How to use addTarget method in swift 3

Question

here is my button object       let loginRegisterButton UIButton         let button   UIButton type   system      button backgroundColor   UIColor r  50   g  80  b  130      button setTitle  Register   for   normal      button translatesAutoresizingMaskIntoConstraints   false     button setTitleColor  white  for   normal      button addTarget self  action  selector handleRegister   for   touchUpInside      return button       and here is my function       func handleRegister         FIRAuth auth    createUser withEmail  email  password  password completion     user  error  in          if error    nil           print  Error Occured             else          print  Successfully Authenticated                       I m getting compile error  if addTarget removed it compiles successfully

User · Answer

Try with swift 3    cell TaxToolTips tag   indexPath row         cell TaxToolTips addTarget self  action   selector InheritanceTaxViewController displayToolTipDetails       for  touchUpInside      objc func displayToolTipDetails   sender   UIButton            print sender tag          let tooltipString   TaxToolTipsArray sender tag          self displayMyAlertMessage userMessage  tooltipString  status  202

User · Answer

Try this   button addTarget self  action  selector handleRegister     for   touchUpInside      Just add parenthesis with name of method   Also you can refer link   Value of type   39 CustomButton  39  has no member   39 touchDown  39

User · Answer

let button  UIButton   UIButton       button setImage UIImage named  imagename    for   normal      button addTarget self  action  selector YourClassName backAction  sender     for   touchUpInside       button frame   CGRect init x  5  y  100  width  45  height  45      view addSubview button        objc public func backAction  sender  UIButton

User · Answer

In swift 3 use this -  object  addTarget objectWhichHasMethod  action   selector classWhichHasMethod yourMethod   for  someUIControlEvents    For example from my code  -  self datePicker  addTarget self  action  selector InfoTableViewCell datePickerValueChanged   for   valueChanged    Just give a   after method name if you want the sender as parameter

User · Answer

Try this with Swift 4  buttonSection addTarget self  action   selector actionWithParam       for   touchUpInside   objc func actionWithParam sender  UIButton                buttonSection addTarget self  action   selector actionWithoutParam   for   touchUpInside   objc func actionWithoutParam

User · Answer

Instead of   let loginRegisterButton UIButton                  Try   lazy var loginRegisterButton UIButton                  That should fix the compile error

User · Answer

Yes  don t add      if there is no param  button addTarget self  action  selector handleRegister   for   touchUpInside      and if you want to get the sender  button addTarget self  action  selector handleRegister       for   touchUpInside     func handleRegister sender  UIButton                Edit   button addTarget self  action  selector handleRegister       for   touchUpInside    no longer works  you need to replace   in the selector with a variable name you used in the function header  in this case it would be sender  so the working code becomes   button addTarget self  action  selector handleRegister sender     for   touchUpInside

User · Answer

Try this with Swift 3   button addTarget self  action  selector ClassName handleRegister sender     for   touchUpInside    Good luck

User · Answer

the Demo from Apple document  https   developer apple com documentation swift using objective-c runtime features in swift    import UIKit class MyViewController  UIViewController       let myButton   UIButton frame  CGRect x  0  y  0  width  100  height  50        override init nibName nibNameOrNil  NSNib Name   bundle nibBundleOrNil  Bundle             super init nibName  nibNameOrNil  bundle  nibBundleOrNil             without parameter style         let action    selector MyViewController tappedButton             with parameter style             selector MyViewController tappedButton              myButton addTarget self  action  action  forControlEvents   touchUpInside              objc func tappedButton   sender  UIButton             print  tapped button              required init  coder  NSCoder            super init coder  coder

User · Answer

The poster s second comment from September 21st is spot on   For those who may be coming to this thread later with the same problem as the poster  here is a brief explanation   The other answers are good to keep in mind  but do not address the common issue encountered by this code   In Swift  declarations made with the let keyword are constants   Of course if you were going to add items to an array  the array can t be declared as a constant  but a segmented control should be fine  right    Not if you reference the completed segmented control in its declaration     Referencing the object  in this case a UISegmentedControl  but this also happens with UIButton  in its declaration when you say  addTarget and let the target be self  things crash   Why   Because self is in the midst of being defined   But we do want to define behaviour as part of the object    Declare it lazily as a variable with var   The lazy fools the compiler into thinking that self is well defined - it silences your compiler from caring at the time of declaration   Lazily declared variables don t get set until they are first called   So in this situation  lazy lets you use the notion of self without issue while you set up the object  and then when your object gets a  touchUpInside or  valueChanged or whatever your 3rd argument is in your  addTarget    THEN it calls on the notion of self  which at that point is fully established and totally prepared to be a valid target   So it lets you be lazy in declaring your variable   In cases like these  I think they could give us a keyword like necessary  but it is generally seen as a lazy  sloppy practice and you don t want to use it all over your code  though it may have its place in this sort of situation   What it   There is no lazy let in Swift  no lazy for constants    Here is the Apple documentation on lazy   Here is the Apple on variables and constants   There is a little more in their Language Reference under Declarations

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