How to update the constant height constraint of a UIView programmatically

Question

I have a UIView and I set the constraints using Xcode Interface Builder  Now I need to update that UIView instance s height constant programmatically  There is a function that goes like myUIView updateConstraints    but I don t know how to use it

User · Answer

First connect the Height constraint in to our viewcontroller for creating IBOutlet like the below code shown

@IBOutlet weak var select_dateHeight: NSLayoutConstraint!

then put the below code in view did load or inside any actions

self.select_dateHeight.constant = 0 // we can change the height value

if it is inside a button click

@IBAction func Feedback_button(_ sender: Any) {
 self.select_dateHeight.constant = 0

}

User · Answer

Create an IBOutlet of NSLayoutConstraint of yourView and update the constant value accordingly the condition specifies     Connect them from Interface   IBOutlet viewHeight  NSLayoutConstraint    IBOutlet view  UIView   private func updateViewHeight height Int      guard let aView   view  aViewHeight   viewHeight else        return         aViewHeight constant   height    aView layoutIfNeeded

User · Answer

Drag the constraint into your VC as an IBOutlet  Then you can change its associated value  and other properties  check the documentation     IBOutlet myConstraint   NSLayoutConstraint   IBOutlet myView   UIView   func updateConstraints            You should handle UI updates on the main queue  whenever possible     DispatchQueue main async           self myConstraint constant   10         self myView layoutIfNeeded

User · Answer

Change HeightConstraint and WidthConstraint Without creating IBOutlet   Note  Assign height or width constraint in Storyboard or XIB file  after fetching this Constraint using this extension   You can use this extension to fetch a height and width Constraint   extension UIView    var heightConstraint  NSLayoutConstraint        get           return constraints first where                 0 firstAttribute     height  amp  amp   0 relation     equal                      set   setNeedsLayout        var widthConstraint  NSLayoutConstraint        get           return constraints first where                 0 firstAttribute     width  amp  amp   0 relation     equal                      set   setNeedsLayout            You can use   yourView heightConstraint  constant   newValue

User · Answer

To update a layout constraint you only need to update the constant property and call layoutIfNeeded after   myConstraint constant   newValue myView layoutIfNeeded

User · Answer

If the above method does not work then make sure you update it in Dispatch main async   block  You do not need to call layoutIfNeeded   method then

User · Answer

If you have a view with multiple constrains  a much easier way without having to create multiple outlets would be   In interface builder  give each constraint you wish to modify an identifier     Then in code you can modify multiple constraints like so   for constraint in self view constraints       if constraint identifier     myConstraint           constraint constant   50         myView layoutIfNeeded     You can give multiple constrains the same identifier thus allowing you to group together constrains and modify all at once

User · Answer

Select the height constraint from the Interface builder and take an outlet of it  So  when you want to change the height of the view you can use the below code   yourHeightConstraintOutlet constant   someValue yourView layoutIfNeeded     Method updateConstraints   is an instance method of UIView  It is helpful when you are setting the constraints programmatically  It updates constraints for the view  For more detail click here

User · Answer

You can update your constraint with a smooth animation if you want  see the chunk of code below    heightOrWidthConstraint constant   100 UIView animate withDuration  animateTime  animations   self view layoutIfNeeded

[swift] How to update the constant height constraint of a UIView programmatically?

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