How to add constraints programmatically using Swift

Question

I m trying to figure this out since last week without going any step further  Ok  so I need to apply some constraints programmatically in Swift to a UIView using this code   var new view UIView    UIView frame  CGRectMake 0  0  100  100    new view backgroundColor   UIColor redColor    view addSubview new view    var constX NSLayoutConstraint   NSLayoutConstraint item  new view  attribute  NSLayoutAttribute CenterX  relatedBy  NSLayoutRelation Equal  toItem  self view  attribute  NSLayoutAttribute CenterX  multiplier  1  constant  0   self view addConstraint constX    var constY NSLayoutConstraint   NSLayoutConstraint item  new view  attribute  NSLayoutAttribute CenterY  relatedBy  NSLayoutRelation Equal  toItem  self view  attribute  NSLayoutAttribute CenterY  multiplier  1  constant  0   self view addConstraint constY    var constW NSLayoutConstraint   NSLayoutConstraint item  new view  attribute  NSLayoutAttribute Width  relatedBy  NSLayoutRelation Equal  toItem  new view  attribute  NSLayoutAttribute Width  multiplier  1  constant  0   self view addConstraint constW    var constH NSLayoutConstraint   NSLayoutConstraint item  new view  attribute  NSLayoutAttribute Height  relatedBy  NSLayoutRelation Equal  toItem  new view  attribute  NSLayoutAttribute Height  multiplier  1  constant  0   self view addConstraint constH     But Xcode returns this weird output   2014-10-03 09 48 12 657 Test 35088 2454916  Unable to simultaneously satisfy constraints   Probably at least one of the constraints in the following list is one you don t want  Try this   1  look at each constraint and try to figure out which you don t expect   2  find the code that added the unwanted constraint or constraints and fix it   Note  If you re seeing NSAutoresizingMaskLayoutConstraints that you don t understand  refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints       lt NSLayoutConstraint 0x7fa4ea446830 UIView 0x7fa4ea429290 centerX    UIView 0x7fa4ea4470f0 centerX gt      lt NSAutoresizingMaskLayoutConstraint 0x7fa4ea4516c0 h -- amp  v -- amp  UIView 0x7fa4ea429290 midX      50 gt      lt NSLayoutConstraint 0x7fa4ea452830  UIView-Encapsulated-Layout-Width  H  UIView 0x7fa4ea4470f0 375   gt      lt NSAutoresizingMaskLayoutConstraint 0x7fa4ea446db0 h - amp - v - amp -  UIView-Encapsulated-Layout-Left  H  - 0 - UIView 0x7fa4ea4470f0     Names      UIWindow 0x7fa4ea444b20   gt      Will attempt to recover by breaking constraint  lt NSLayoutConstraint 0x7fa4ea446830 UIView 0x7fa4ea429290 centerX    UIView 0x7fa4ea4470f0 centerX gt   Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger  The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in  lt UIKit UIView h gt  may also be helpful   2014-10-03 09 48 12 658 Test 35088 2454916  Unable to simultaneously satisfy constraints   Probably at least one of the constraints in the following list is one you don t want  Try this   1  look at each constraint and try to figure out which you don t expect   2  find the code that added the unwanted constraint or constraints and fix it   Note  If you re seeing NSAutoresizingMaskLayoutConstraints that you don t understand  refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints      lt NSLayoutConstraint 0x7fa4ea44d160 UIView 0x7fa4ea429290 centerY    UIView 0x7fa4ea4470f0 centerY gt      lt NSAutoresizingMaskLayoutConstraint 0x7fa4ea451b30 h -- amp  v -- amp  UIView 0x7fa4ea429290 midY      50 gt      lt NSLayoutConstraint 0x7fa4ea44cf00  UIView-Encapsulated-Layout-Height  V  UIView 0x7fa4ea4470f0 667   gt      lt NSAutoresizingMaskLayoutConstraint 0x7fa4ea452700 h - amp - v - amp -  UIView-Encapsulated-Layout-Top  V  - 0 - UIView 0x7fa4ea4470f0    Names      UIWindow 0x7fa4ea444b20   gt      Will attempt to recover by breaking constraint  lt NSLayoutConstraint 0x7fa4ea44d160 UIView 0x7fa4ea429290 centerY    UIView 0x7fa4ea4470f0 centerY gt   Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger  The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in  lt UIKit UIView h gt  may also be helpful    Can you help me  Thanks a lot

User · Answer

Do you plan to have a squared UIView of width  100 and Height  100 centered inside the UIView of an UIViewController  If so  you may try one of the 6 following Auto Layout styles  Swift 5   iOS 12 2    1  Using NSLayoutConstraint initializer override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let horizontalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerX  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerX  multiplier  1  constant  0      let verticalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerY  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerY  multiplier  1  constant  0      let widthConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute width  relatedBy  NSLayoutConstraint Relation equal  toItem  nil  attribute  NSLayoutConstraint Attribute notAnAttribute  multiplier  1  constant  100      let heightConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute height  relatedBy  NSLayoutConstraint Relation equal  toItem  nil  attribute  NSLayoutConstraint Attribute notAnAttribute  multiplier  1  constant  100      view addConstraints  horizontalConstraint  verticalConstraint  widthConstraint  heightConstraint       override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let horizontalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerX  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerX  multiplier  1  constant  0      let verticalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerY  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerY  multiplier  1  constant  0      let widthConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute width  relatedBy  NSLayoutConstraint Relation equal  toItem  nil  attribute  NSLayoutConstraint Attribute notAnAttribute  multiplier  1  constant  100      let heightConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute height  relatedBy  NSLayoutConstraint Relation equal  toItem  nil  attribute  NSLayoutConstraint Attribute notAnAttribute  multiplier  1  constant  100      NSLayoutConstraint activate  horizontalConstraint  verticalConstraint  widthConstraint  heightConstraint       override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerX  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerX  multiplier  1  constant  0  isActive   true     NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerY  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerY  multiplier  1  constant  0  isActive   true     NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute width  relatedBy  NSLayoutConstraint Relation equal  toItem  nil  attribute  NSLayoutConstraint Attribute notAnAttribute  multiplier  1  constant  100  isActive   true     NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute height  relatedBy  NSLayoutConstraint Relation equal  toItem  nil  attribute  NSLayoutConstraint Attribute notAnAttribute  multiplier  1  constant  100  isActive   true     2  Using Visual Format Language override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let views     quot view quot   view    quot newView quot   newView      let horizontalConstraints   NSLayoutConstraint constraints withVisualFormat   quot H  view -  lt  0 - newView 100   quot   options  NSLayoutConstraint FormatOptions alignAllCenterY  metrics  nil  views  views      let verticalConstraints   NSLayoutConstraint constraints withVisualFormat   quot V  view -  lt  0 - newView 100   quot   options  NSLayoutConstraint FormatOptions alignAllCenterX  metrics  nil  views  views      view addConstraints horizontalConstraints      view addConstraints verticalConstraints      override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let views     quot view quot   view    quot newView quot   newView      let horizontalConstraints   NSLayoutConstraint constraints withVisualFormat   quot H  view -  lt  0 - newView 100   quot   options  NSLayoutConstraint FormatOptions alignAllCenterY  metrics  nil  views  views      let verticalConstraints   NSLayoutConstraint constraints withVisualFormat   quot V  view -  lt  0 - newView 100   quot   options  NSLayoutConstraint FormatOptions alignAllCenterX  metrics  nil  views  views      NSLayoutConstraint activate horizontalConstraints      NSLayoutConstraint activate verticalConstraints      3  Using a mix of NSLayoutConstraint initializer and Visual Format Language override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let views     quot newView quot   newView      let widthConstraints   NSLayoutConstraint constraints withVisualFormat   quot H  newView 100   quot   options  NSLayoutConstraint FormatOptions rawValue  0   metrics  nil  views  views      let heightConstraints   NSLayoutConstraint constraints withVisualFormat   quot V  newView 100   quot   options  NSLayoutConstraint FormatOptions rawValue  0   metrics  nil  views  views      let horizontalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerX  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerX  multiplier  1  constant  0      let verticalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerY  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerY  multiplier  1  constant  0      view addConstraints widthConstraints      view addConstraints heightConstraints      view addConstraints  horizontalConstraint  verticalConstraint       override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let views     quot newView quot   newView      let widthConstraints   NSLayoutConstraint constraints withVisualFormat   quot H  newView 100   quot   options  NSLayoutConstraint FormatOptions rawValue  0   metrics  nil  views  views      let heightConstraints   NSLayoutConstraint constraints withVisualFormat   quot V  newView 100   quot   options  NSLayoutConstraint FormatOptions rawValue  0   metrics  nil  views  views      let horizontalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerX  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerX  multiplier  1  constant  0      let verticalConstraint   NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerY  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerY  multiplier  1  constant  0      NSLayoutConstraint activate widthConstraints      NSLayoutConstraint activate heightConstraints      NSLayoutConstraint activate  horizontalConstraint  verticalConstraint       override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   false     let views     quot newView quot   newView      let widthConstraints   NSLayoutConstraint constraints withVisualFormat   quot H  newView 100   quot   options  NSLayoutConstraint FormatOptions rawValue  0   metrics  nil  views  views      let heightConstraints   NSLayoutConstraint constraints withVisualFormat   quot V  newView 100   quot   options  NSLayoutConstraint FormatOptions rawValue  0   metrics  nil  views  views      NSLayoutConstraint activate widthConstraints      NSLayoutConstraint activate heightConstraints      NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerX  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerX  multiplier  1  constant  0  isActive   true     NSLayoutConstraint item  newView  attribute  NSLayoutConstraint Attribute centerY  relatedBy  NSLayoutConstraint Relation equal  toItem  view  attribute  NSLayoutConstraint Attribute centerY  multiplier  1  constant  0  isActive   true     4  Using UIView AutoresizingMask Note  Springs and Struts will be translated into corresponding auto layout constraints at runtime  override func viewDidLoad         let newView   UIView frame  CGRect x  0  y  0  width  100  height  100       newView backgroundColor   UIColor red     view addSubview newView       newView translatesAutoresizingMaskIntoConstraints   true     newView center   CGPoint x  view bounds midX  y  view bounds midY      newView autoresizingMask    UIView AutoresizingMask flexibleLeftMargin  UIView AutoresizingMask flexibleRightMargin  UIView AutoresizingMask flexibleTopMargin  UIView AutoresizingMask flexibleBottomMargin      5  Using NSLayoutAnchor override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView           newView translatesAutoresizingMaskIntoConstraints   false     let horizontalConstraint   newView centerXAnchor constraint equalTo  view centerXAnchor      let verticalConstraint   newView centerYAnchor constraint equalTo  view centerYAnchor      let widthConstraint   newView widthAnchor constraint equalToConstant  100      let heightConstraint   newView heightAnchor constraint equalToConstant  100      view addConstraints  horizontalConstraint  verticalConstraint  widthConstraint  heightConstraint       override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView           newView translatesAutoresizingMaskIntoConstraints   false     let horizontalConstraint   newView centerXAnchor constraint equalTo  view centerXAnchor      let verticalConstraint   newView centerYAnchor constraint equalTo  view centerYAnchor      let widthConstraint   newView widthAnchor constraint equalToConstant  100      let heightConstraint   newView heightAnchor constraint equalToConstant  100      NSLayoutConstraint activate  horizontalConstraint  verticalConstraint  widthConstraint  heightConstraint       override func viewDidLoad         let newView   UIView       newView backgroundColor   UIColor red     view addSubview newView           newView translatesAutoresizingMaskIntoConstraints   false     newView centerXAnchor constraint equalTo  view centerXAnchor  isActive   true     newView centerYAnchor constraint equalTo  view centerYAnchor  isActive   true     newView widthAnchor constraint equalToConstant  100  isActive   true     newView heightAnchor constraint equalToConstant  100  isActive   true     6  Using intrinsicContentSize and NSLayoutAnchor import UIKit  class CustomView  UIView            override var intrinsicContentSize  CGSize           return CGSize width  100  height  100                class ViewController  UIViewController            override func viewDidLoad             let newView   CustomView           newView backgroundColor   UIColor red         view addSubview newView                   newView translatesAutoresizingMaskIntoConstraints   false         let horizontalConstraint   newView centerXAnchor constraint equalTo  view centerXAnchor          let verticalConstraint   newView centerYAnchor constraint equalTo  view centerYAnchor          NSLayoutConstraint activate  horizontalConstraint  verticalConstraint                  Result

User · Answer

If you find the above to be ugly  You should consider using a DSL for constraints  Such as SnapKit Makes constraint API much more user-friendly  view snp makeConstraints   make in     make edges equalToSuperview

User · Answer

Try this elegant UIView extension for constraints  You can do constraints easy as     - firstView coverWholeSuperview    - firstView constraints size  CGSize width  44  height  44   centerX  view centerXAnchor  centerY  view centerXAnchor   - firstView constraints top  view topAnchor                            leading  secondView leadingAnchor                            bottom  view bottomAnchor                            trailing  secondView trailingAnchor                            padding  UIEdgeInsets top  12  left  12  bottom  12  right  12      Here is extension  just copy it to your project   extension UIView           Attaches all sides of the receiver to its parent view     func coverWholeSuperview margin  CGFloat   0 0            let view   superview         layoutAttachTop to  view  margin  margin          layoutAttachBottom to  view  margin  margin          layoutAttachLeading to  view  margin  margin          layoutAttachTrailing to  view  margin  margin                  Attaches the top of the current view to the given view s top if it s a superview of the current view         or to it s bottom if it s not  assuming this is then a sibling view        discardableResult     func layoutAttachTop to  UIView    nil  margin  CGFloat   0 0  - gt  NSLayoutConstraint            let view  UIView    to    superview         let isSuperview   view    superview         let constraint   NSLayoutConstraint item  self  attribute   top  relatedBy   equal                                              toItem  view  attribute  isSuperview    top    bottom  multiplier  1 0                                              constant  margin          superview  addConstraint constraint           return constraint                Attaches the bottom of the current view to the given view      discardableResult     func layoutAttachBottom to  UIView    nil  margin  CGFloat   0 0  priority  UILayoutPriority    nil  - gt  NSLayoutConstraint            let view  UIView    to    superview         let isSuperview    view    superview     false         let constraint   NSLayoutConstraint item  self  attribute   bottom  relatedBy   equal                                              toItem  view  attribute  isSuperview    bottom    top  multiplier  1 0                                              constant  -margin          if let priority   priority               constraint priority   priority                   superview  addConstraint constraint           return constraint                Attaches the leading edge of the current view to the given view      discardableResult     func layoutAttachLeading to  UIView    nil  margin  CGFloat   0 0  - gt  NSLayoutConstraint            let view  UIView    to    superview         let isSuperview    view    superview     false         let constraint   NSLayoutConstraint item  self  attribute   leading  relatedBy   equal                                              toItem  view  attribute  isSuperview    leading    trailing  multiplier  1 0                                              constant  margin          superview  addConstraint constraint           return constraint                Attaches the trailing edge of the current view to the given view      discardableResult     func layoutAttachTrailing to  UIView    nil  margin  CGFloat   0 0  priority  UILayoutPriority    nil  - gt  NSLayoutConstraint            let view  UIView    to    superview         let isSuperview    view    superview     false         let constraint   NSLayoutConstraint item  self  attribute   trailing  relatedBy   equal                                              toItem  view  attribute  isSuperview    trailing    leading  multiplier  1 0                                              constant  -margin          if let priority   priority               constraint priority   priority                   superview  addConstraint constraint           return constraint               For anchoring View     struct AnchoredConstraints           var top  leading  bottom  trailing  width  height  centerX  centerY  NSLayoutConstraint              discardableResult     func constraints top  NSLayoutYAxisAnchor    nil  leading  NSLayoutXAxisAnchor    nil  bottom  NSLayoutYAxisAnchor    nil                  trailing  NSLayoutXAxisAnchor    nil  padding  UIEdgeInsets    zero  size  CGSize    zero                  centerX  NSLayoutXAxisAnchor    nil  centerY  NSLayoutYAxisAnchor    nil                  centerXOffset  CGFloat   0  centerYOffset  CGFloat   0  - gt  AnchoredConstraints            translatesAutoresizingMaskIntoConstraints   false         var anchoredConstraints   AnchoredConstraints            if let top   top               anchoredConstraints top   topAnchor constraint equalTo  top  constant  padding top                     if let leading   leading               anchoredConstraints leading   leadingAnchor constraint equalTo  leading  constant  padding left                     if let bottom   bottom               anchoredConstraints bottom   bottomAnchor constraint equalTo  bottom  constant  -padding bottom                     if let trailing   trailing               anchoredConstraints trailing   trailingAnchor constraint equalTo  trailing  constant  -padding right                     if size width    0               anchoredConstraints width   widthAnchor constraint equalToConstant  size width                     if size height    0               anchoredConstraints height   heightAnchor constraint equalToConstant  size height                     if let centerX   centerX               anchoredConstraints centerX   centerXAnchor constraint equalTo  centerX  constant  centerXOffset                     if let centerY   centerY               anchoredConstraints centerY   centerYAnchor constraint equalTo  centerY  constant  centerYOffset                      anchoredConstraints top  anchoredConstraints leading  anchoredConstraints bottom           anchoredConstraints trailing  anchoredConstraints width           anchoredConstraints height  anchoredConstraints centerX           anchoredConstraints centerY  forEach    0  isActive   true            return anchoredConstraints

User · Answer

Auto layout is realized by applying constraints on images  Use NSLayoutConstraint  It is possible to implement an ideal and beautiful design on all devices  Please try the code below  import UIKit  class ViewController  UIViewController    override func viewDidLoad     super viewDidLoad    let myImageView UIImageView   UIImageView   myImageView backgroundColor   UIColor red myImageView image   UIImage named  quot sample dog quot    myImageView translatesAutoresizingMaskIntoConstraints   false myImageView layer borderColor   UIColor red cgColor myImageView layer borderWidth   10 self view addSubview myImageView           view removeConstraints view constraints    view addConstraint NSLayoutConstraint  item  myImageView  attribute   top  relatedBy   equal  toItem  view  attribute   top  multiplier  1  constant 100          view addConstraint NSLayoutConstraint  item  myImageView  attribute   centerX  relatedBy   equal  toItem  view  attribute   centerX  multiplier  1  constant 0         view addConstraint NSLayoutConstraint  item  myImageView  attribute   height  relatedBy   equal  toItem  view  attribute   width  multiplier  0 5  constant 40        view addConstraint NSLayoutConstraint  item  myImageView  attribute   width  relatedBy   equal  toItem  view  attribute   width  multiplier  0 5  constant 40           override func didReceiveMemoryWarning         super didReceiveMemoryWarning

User · Answer

You can use Snapkit to set constraints programmatically  class ViewController  UIViewController            let rectView  UIView   UIView frame  CGRect x  0  y  0  width  100  height  100            override func viewDidLoad             super viewDidLoad           setupViews                  private func setupViews             rectView backgroundColor    red         view addSubview rectView           rectView snp makeConstraints              0 center equalToSuperview

User · Answer

Basically it involved 3 steps  fileprivate func setupName           lblName text    Hello world          Step 1     lblName translatesAutoresizingMaskIntoConstraints   false        Step 2     self view addSubview lblName         Step 3     NSLayoutConstraint activate           lblName centerXAnchor constraint equalTo  self view centerXAnchor           lblName centerYAnchor constraint equalTo  self view centerYAnchor             This puts label  hello world  in center of screen   Please refer link Autolayout constraints programmatically

User · Answer

It helps me to learn visually  so this is a supplemental answer   Boilerplate code  override func viewDidLoad         super viewDidLoad        let myView   UIView       myView backgroundColor   UIColor blue     myView translatesAutoresizingMaskIntoConstraints   false     view addSubview myView          Add constraints code here                Each of the following examples are independent of the others   Pin left edge  myView leading   leadingMargin   20    Method 1  Anchor Style  let margins   view layoutMarginsGuide myView leadingAnchor constraint equalTo  margins leadingAnchor  constant  20  isActive   true    In addition to leadingAnchor  there is also trailingAnchor  topAnchor  and bottomAnchor    Method 2  NSLayoutConstraint Style  NSLayoutConstraint item  myView  attribute  NSLayoutAttribute leading  relatedBy  NSLayoutRelation equal  toItem  view  attribute  NSLayoutAttribute leadingMargin  multiplier  1 0  constant  20 0  isActive   true    In addition to  leading there is also  trailing   top  and  bottom    In addition to  leadingMargin there is also  trailingMargin   topMargin  and  bottomMargin    Set Width and Height  width   200 height   100    Method 1  Anchor Style  myView widthAnchor constraint equalToConstant  200  isActive   true myView heightAnchor constraint equalToConstant  100  isActive   true   Method 2  NSLayoutConstraint Style  NSLayoutConstraint item  myView  attribute  NSLayoutAttribute width  relatedBy  NSLayoutRelation equal  toItem  nil  attribute  NSLayoutAttribute notAnAttribute  multiplier  1  constant  200  isActive   true NSLayoutConstraint item  myView  attribute  NSLayoutAttribute height  relatedBy  NSLayoutRelation equal  toItem  nil  attribute  NSLayoutAttribute notAnAttribute  multiplier  1  constant  100  isActive   true   Center in container  myView centerX   centerX myView centerY   centerY    Method 1  Anchor Style  myView centerXAnchor constraint equalTo  view centerXAnchor  isActive   true myView centerYAnchor constraint equalTo  view centerYAnchor  isActive   true   Method 2  NSLayoutConstraint Style  NSLayoutConstraint item  myView  attribute  NSLayoutAttribute centerX  relatedBy  NSLayoutRelation equal  toItem  view  attribute  NSLayoutAttribute centerX  multiplier  1  constant  0  isActive   true NSLayoutConstraint item  myView  attribute  NSLayoutAttribute centerY  relatedBy  NSLayoutRelation equal  toItem  view  attribute  NSLayoutAttribute centerY  multiplier  1  constant  0  isActive   true   Notes   Anchor style is the preferred method over NSLayoutConstraint Style  however it is only available from iOS 9  so if you are supporting iOS 8 then you should still use NSLayoutConstraint Style  The examples above showed just the one or two constraints that were being focused on  However  in order to properly place myView in my test project I needed to have four constraints    Further Reading   Programmatically Creating Constraints documentation

User · Answer

var xCenterConstraint   NSLayoutConstraint      var yCenterConstraint  NSLayoutConstraint    xCenterConstraint   NSLayoutConstraint item  self view  attribute   CenterX  relatedBy   Equal  toItem   Your view NAme   attribute   CenterX  multiplier  1  constant  0              self view addConstraint xCenterConstraint    yCenterConstraint   NSLayoutConstraint item  self view  attribute   CenterY  relatedBy   Equal  toItem   Your view Name   attribute   CenterY  multiplier  1  constant  0              self view addConstraint yCenterConstraint

User · Answer

Would like to add some theoretical concept to  Imanou Petit   s answer  so that one can understand how auto layout works   To understand auto layout consider your view as rubber s object which is shrinked initially   To place an object on screen we need 4 mandatory things     X coordinate of object  horizontal position   Y coordinate of object    vertical position   Object   s Width Object   s Height    1 X coordinate  There are multiple ways of giving x coordinates to a view   Such as Leading constraint  Trailing constraint   Horizontally centre etc   2 Y coordinate  There are multiple ways of giving y coordinates to a view    Such as Top constraint  Bottom constraint   Vertical centre etc   3 Object s width  There are two ways of giving width constrain to a view    a  Add fixed width constraint  consider this constraint as iron rod of fixed width and you have hooked your rubber   s object horizontally with it so rubber   s object don   t shrink or expand   b  Do not add any width constraint but add x coordinate constraint to both end of view trailing and leading  these two constraints will expand shrink your rubber   s object by pulling pushing it from both end  leading and trailing     4 Object s height  Similar to width  there are two ways of giving height constraint to a view as well    a  Add fixed height constraint  consider this constraints as iron rod of fixed height and you have hooked your rubber   s object vertically with it so rubber   s object don   t shrink or expand   b  Do not add any height constraint but add x coordinate constraint to both end of view top and bottom  these two constraints will expand shrink your rubber   s object pulling pushing it from both end  top and bottom

User · Answer

If you want to fill your super view then I suggest the swifty way       view translatesAutoresizingMaskIntoConstraints   false     let attributes   NSLayoutAttribute      top   bottom   right   left      NSLayoutConstraint activate attributes map           NSLayoutConstraint item  view  attribute   0  relatedBy   equal  toItem  view superview  attribute   0  multiplier  1  constant  0           Other wise if you need non equal constraints check out NSLayoutAnchor as of iOS 9   Its often much easier to read that using NSLayoutConstraint directly       view translatesAutoresizingMaskIntoConstraints   false     view topAnchor constraint equalTo  view superview  topAnchor  isActive   true     view bottomAnchor constraint equalTo  view superview  bottomAnchor  isActive   true     view leadingAnchor constraint equalTo  view superview  leadingAnchor  constant  10  isActive   true     view trailingAnchor constraint equalTo  view superview  trailingAnchor  constant  10  isActive   true

User · Answer

This is one way to adding constraints programmatically  override func viewDidLoad                 super viewDidLoad     let myLabel   UILabel           myLabel labelFrameUpdate label  myLabel  text   Welcome User   font  UIFont name   times new roman   size  40    textColor  UIColor red  textAlignment   center  numberOfLines  0  borderWidth  2 0  BorderColor  UIColor red cgColor          self view addSubview myLabel             let myLabelhorizontalConstraint   NSLayoutConstraint item  myLabel  attribute  NSLayoutAttribute centerX  relatedBy  NSLayoutRelation equal  toItem  self view  attribute  NSLayoutAttribute centerX  multiplier  1  constant  0          let myLabelverticalConstraint   NSLayoutConstraint item  myLabel  attribute  NSLayoutAttribute centerY  relatedBy  NSLayoutRelation equal  toItem  self view  attribute  NSLayoutAttribute centerY  multiplier  1  constant  0          let mylabelLeading   NSLayoutConstraint item  myLabel  attribute  NSLayoutAttribute leading  relatedBy  NSLayoutRelation equal  toItem  self view  attribute  NSLayoutAttribute leading  multiplier  1  constant  10          let mylabelTrailing   NSLayoutConstraint item  myLabel  attribute  NSLayoutAttribute trailing  relatedBy  NSLayoutRelation equal  toItem  self view  attribute  NSLayoutAttribute trailing  multiplier  1  constant  -10          let myLabelheightConstraint   NSLayoutConstraint item  myLabel  attribute  NSLayoutAttribute height  relatedBy  NSLayoutRelation equal  toItem  nil  attribute  NSLayoutAttribute notAnAttribute  multiplier  1  constant  50          NSLayoutConstraint activate   myLabelhorizontalConstraint  myLabelverticalConstraint  myLabelheightConstraint mylabelLeading mylabelTrailing       extension UILabel       func labelFrameUpdate label UILabel text String    This is sample Label  font UIFont   UIFont name   times new roman   size  20   textColor UIColor   UIColor red textAlignment NSTextAlignment    center numberOfLines Int   0 borderWidth CGFloat   2 0 BorderColor CGColor   UIColor red cgColor           label translatesAutoresizingMaskIntoConstraints   false         label text   text         label font   font         label textColor   textColor         label textAlignment   textAlignment         label numberOfLines   numberOfLines         label layer borderWidth   borderWidth         label layer borderColor   UIColor red cgColor

User · Answer

Updated for Swift 3  import UIKit  class ViewController  UIViewController    let redView  UIView          let view   UIView       view translatesAutoresizingMaskIntoConstraints   false     view backgroundColor    red     return view      override func viewDidLoad         super viewDidLoad        setupViews       setupAutoLayout      func setupViews          view backgroundColor    white     view addSubview redView     func setupAutoLayout             Available from iOS 9 commonly known as Anchoring System for AutoLayout        redView leftAnchor constraint equalTo  view leftAnchor  constant  20  isActive   true     redView rightAnchor constraint equalTo  view rightAnchor  constant  -20  isActive   true      redView centerYAnchor constraint equalTo  view centerYAnchor  isActive   true     redView heightAnchor constraint equalToConstant  300  isActive   true         You can also modified above last two lines as follows by commenting above  amp  uncommenting below lines           redView topAnchor constraint equalTo  view topAnchor  constant  20  isActive   true        redView bottomAnchor constraint equalTo  view bottomAnchor  isActive   true          Type of Constraints         regular use 1 leftAnchor 2 rightAnchor 3 topAnchor    intermediate use 4 widthAnchor 5 heightAnchor 6 bottomAnchor 7 centerXAnchor 8 centerYAnchor    rare use 9 leadingAnchor 10 trailingAnchor etc   note  very project to project

User · Answer

it is a little different in xcode 7 3 1  this is what i come up with         creating the view         let newView   UIView           newView backgroundColor   UIColor redColor           newView translatesAutoresizingMaskIntoConstraints   false         view addSubview newView              creating the constraint              attribute and relation cannot be set directyl you need to create a cariable of them         let layout11   NSLayoutAttribute CenterX         let layout21   NSLayoutRelation Equal         let layout31   NSLayoutAttribute CenterY         let layout41   NSLayoutAttribute Width         let layout51   NSLayoutAttribute Height         let layout61   NSLayoutAttribute NotAnAttribute             defining all the constraint         let horizontalConstraint   NSLayoutConstraint item  newView  attribute  layout11  relatedBy  layout21  toItem  view  attribute  layout11  multiplier  1  constant  0          let verticalConstraint   NSLayoutConstraint item  newView  attribute  layout31  relatedBy  layout21  toItem  view  attribute  layout31  multiplier  1  constant  0          let widthConstraint   NSLayoutConstraint item  newView  attribute  layout41  relatedBy  layout21  toItem  nil  attribute  layout61  multiplier  1  constant  100          let heightConstraint   NSLayoutConstraint item  newView  attribute  layout51  relatedBy  layout21  toItem  nil  attribute  layout61  multiplier  1  constant  100              adding all the constraint         NSLayoutConstraint activateConstraints  horizontalConstraint verticalConstraint widthConstraint heightConstraint

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The problem  as the error message suggests  is that you have constraints of type NSAutoresizingMaskLayoutConstraints that conflict with your explicit constraints  because new view translatesAutoresizingMaskIntoConstraints is set to true   This is the default setting for views you create in code   You can turn it off like this   var new view UIView    UIView frame  CGRectMake 0  0  100  100   new view translatesAutoresizingMaskIntoConstraints   false   Also  your width and height constraints are weird   If you want the view to have a constant width  this is the proper way   new view addConstraint NSLayoutConstraint      item new view  attribute NSLayoutAttribute Width      relatedBy NSLayoutRelation Equal      toItem nil  attribute NSLayoutAttribute NotAnAttribute      multiplier 0  constant 100      Replace 100 by the width you want it to have    If your deployment target is iOS 9 0 or later  you can use this shorter code   new view widthAnchor constraintEqualToConstant 100  active   true   Anyway  for a layout like this  fixed size and centered in parent view   it would be simpler to use the autoresizing mask and let the system translate the mask into constraints   var new view UIView    UIView frame  CGRectMake 0  0  100  100   new view backgroundColor   UIColor redColor    view addSubview new view       This is the default setting but be explicit anyway    new view translatesAutoresizingMaskIntoConstraints   true  new view autoresizingMask      FlexibleTopMargin   FlexibleBottomMargin       FlexibleLeftMargin   FlexibleRightMargin    new view center   CGPointMake view bounds midX  view bounds midY    Note that using autoresizing is perfectly legitimate even when you re also using autolayout   UIKit still uses autoresizing in lots of places internally   The problem is that it s difficult to apply additional constraints to a view that is using autoresizing

User · Answer

Constraints for multiple views in playground    swift 3     var yellowView  UIView      var redView  UIView       override func loadView                 UI          let view   UIView           view backgroundColor    white          yellowView   UIView           yellowView backgroundColor    yellow         view addSubview yellowView           redView   UIView           redView backgroundColor    red         view addSubview redView              Layout         redView translatesAutoresizingMaskIntoConstraints   false         yellowView translatesAutoresizingMaskIntoConstraints   false         NSLayoutConstraint activate               yellowView topAnchor constraint equalTo  view topAnchor  constant  20               yellowView leadingAnchor constraint equalTo  view leadingAnchor  constant  20               yellowView widthAnchor constraint equalToConstant  80               yellowView heightAnchor constraint equalToConstant  80                redView bottomAnchor constraint equalTo  view bottomAnchor  constant  -20               redView trailingAnchor constraint equalTo  view trailingAnchor constant  -20               redView widthAnchor constraint equalToConstant  80               redView heightAnchor constraint equalToConstant  80                          self view   view            In my opinion xcode playground is the best place for learning adding   constraints programmatically

User · Answer

We can easily do this with in swift 5 1  setup 1   subview align to view center subview width height set using float  view addSubview myView1  myView1 translatesAutoresizingMaskIntoConstraints   false NSLayoutConstraint activate       myView1 centerXAnchor constraint equalTo  view centerXAnchor       myView1 centerYAnchor constraint equalTo  view centerYAnchor       myView1 widthAnchor constraint equalToConstant  100       myView1 heightAnchor constraint equalToConstant  100         setup 2   subview align to view leading and top anchor subview width set using view width height      view addSubview myView2      myView2 translatesAutoresizingMaskIntoConstraints   false      NSLayoutConstraint activate           myView2 leadingAnchor constraint equalTo  view leadingAnchor constant  16           myView2 topAnchor constraint equalTo  view safeAreaLayoutGuide topAnchor constant  16           myView2 widthAnchor constraint equalTo  view widthAnchor  multiplier  0 3           myView2 heightAnchor constraint equalTo  view heightAnchor  multiplier  0 3

User · Answer

The error is caused by constrains automatically created from autoresizing mask  they are created because UIView property translatesAutoresizingMaskIntoConstraints is true by default  Consider using BoxView to get rid of all manual constraint creation boilerplate  and make your code concize and readable  To make layout in question with BoxView is very easy  boxView items        new view boxed centerX   centerY   relativeWidth 1 0  relativeHeight 1 0

User · Answer

the following code works for me in this scenario  an UIImageView forced landscape      imagePreview  isUserInteractionEnabled   true     imagePreview  isExclusiveTouch   true     imagePreview  contentMode   UIView ContentMode scaleAspectFit             Remove all constraints     imagePreview  removeAllConstraints               Add the new constraints     let guide   view safeAreaLayoutGuide     imagePreview  translatesAutoresizingMaskIntoConstraints   false     imagePreview  leadingAnchor constraint equalTo  guide leadingAnchor  isActive   true     imagePreview  trailingAnchor constraint equalTo  guide trailingAnchor  isActive   true     imagePreview  heightAnchor constraint equalTo  guide heightAnchor  multiplier  1 0  isActive   true  where removeAllConstraints is an extension extension UIView            func removeAllConstraints             var  superview   self superview                  func removeAllConstraintsFromView view  UIView    for c in view constraints   view removeConstraint c                       while let superview    superview               for constraint in superview constraints                                    if let first   constraint firstItem as  UIView  first    self                       superview removeConstraint constraint                                                     if let second   constraint secondItem as  UIView  second    self                       superview removeConstraint constraint                                                            superview   superview superview                            self removeConstraints self constraints          self translatesAutoresizingMaskIntoConstraints   true

User · Answer

You are adding all defined constraints to self view which is wrong  as width and height constraint should be added to your newView   Also  as I understand you want to set constant width and height 100 100  In this case you should change your code to   var constW   NSLayoutConstraint item  newView       attribute   Width       relatedBy   Equal       toItem  nil       attribute   NotAnAttribute       multiplier  1       constant  100  newView addConstraint constW   var constH   NSLayoutConstraint item  newView       attribute   Height       relatedBy   Equal       toItem  nil       attribute   NotAnAttribute       multiplier  1       constant  100  newView addConstraint constH

[ios] How to add constraints programmatically using Swift

1. Using `NSLayoutConstraint` initializer

2. Using Visual Format Language

3. Using a mix of `NSLayoutConstraint` initializer and Visual Format Language

4. Using `UIView.AutoresizingMask`

5. Using `NSLayoutAnchor`

6. Using `intrinsicContentSize` and `NSLayoutAnchor`

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