blocks|key|3973906|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3973907|button.addTarget(self,+action:#selector(handleRegister()),+for:+.touchUpInside).+|code-block|syntax|javascript|3973908|只需添加带有方法名称的括号即可。|3973909|你也可以参考链接：Value+of+type+'CustomButton'+has+no+member+'touchDown'|offset|length|3973910|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/39509556/value-of-type-custombutton-has-no-member-touchdown/39509985#39509985^0|0|0|0|9|1I|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

Try this 

<pre><code>button.addTarget(self, action:#selector(handleRegister()), for: .touchUpInside). 
</code></pre>

Just add parenthesis with name of method.

Also you can refer link : <a href="https://stackoverflow.com/questions/39509556/value-of-type-custombutton-has-no-member-touchdown/39509985#39509985">Value of type &#39;CustomButton&#39; has no member &#39;touchDown&#39;</a>

blocks|key|3973934|text|是，如果没有参数，不要添加"()“|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3973935|button.addTarget(self,+action:#selector(handleRegister),+for:+.touchUpInside).+|code-block|syntax|javascript|3973936|如果你想让发送者|3973937|button.addTarget(self,+action:#selector(handleRegister(_:)),+for:+.touchUpInside).+

func+handleRegister(sender:+UIButton){
+++//...
}|3973938|编辑：|3973939|button.addTarget(self,+action:#selector(handleRegister(_:)),+for:+.touchUpInside)|3973940|不再起作用，您需要将选择器中的_替换为您在函数头中使用的变量名，在本例中它将是sender，因此工作代码为：|offset|length|style|CODE|3973941|button.addTarget(self,+action:#selector(handleRegister(sender:)),+for:+.touchUpInside)|3973942|entityMap^0|0|0|0|0|0|0|F|1|13|6|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|14|8|@$Q|15|R|16|S|T]|$Q|17|R|18|S|T]]|9|@]|A|$]]|$1|U|3|V|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|W|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|X|$]]

Yes, don't add "()" if there is no param

<pre><code>button.addTarget(self, action:#selector(handleRegister), for: .touchUpInside). 
</code></pre>

and if you want to get the sender

<pre><code>button.addTarget(self, action:#selector(handleRegister(_:)), for: .touchUpInside). 

func handleRegister(sender: UIButton){
 //...
}
</code></pre>

Edit:

<pre><code>button.addTarget(self, action:#selector(handleRegister(_:)), for: .touchUpInside)
</code></pre>

no longer works, you need to replace <code>_</code> in the selector with a variable name you used in the function header, in this case it would be <code>sender</code>, so the working code becomes:

<pre><code>button.addTarget(self, action:#selector(handleRegister(sender:)), for: .touchUpInside)
</code></pre>

blocks|key|1549757|text|在swift+3中使用这个-|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1549758|object?.addTarget(objectWhichHasMethod,+action:+#selector(classWhichHasMethod.yourMethod),+for:+someUIControlEvents)|code-block|syntax|javascript|1549759|例如(来自我的代码)-|1549760|self.datePicker?.addTarget(self,+action:#selector(InfoTableViewCell.datePickerValueChanged),+for:+.valueChanged)|1549761|如果你想把发送者作为参数，只需在方法名后加上一个:即可。|offset|length|style|CODE|1549762|entityMap^0|0|0|0|0|O|1|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

In swift 3 use this -

<pre><code>object?.addTarget(objectWhichHasMethod, action: #selector(classWhichHasMethod.yourMethod), for: someUIControlEvents)
</code></pre>

For example(from my code) -

<pre><code>self.datePicker?.addTarget(self, action:#selector(InfoTableViewCell.datePickerValueChanged), for: .valueChanged)
</code></pre>

Just give a <code>:</code> after method name if you want the sender as parameter.

blocks|key|1864035|text|发帖者从9月21日开始的第二条评论是对的。对于那些以后可能会带着与发帖者相同的问题来到这个帖子的人，这里有一个简短的解释。记住其他答案是很好的，但不能解决此代码遇到的常见问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1864036|在Swift中，使用let关键字进行的声明是常量。当然，如果要将项添加到数组中，则不能将数组声明为常量，但分段控件应该可以，对吧？！如果在声明中引用已完成的分段控件，则不会。|offset|length|style|CODE|1864037|在其声明中引用对象(在本例中为UISegmentedControl，但这也发生在UIButton中)时，当您指定.addTarget并将目标设为self时，事情就会崩溃。为什么？因为self正在被定义中。但我们确实希望将行为定义为对象的一部分。用var将其作为变量延迟声明为。lazy欺骗编译器，使其认为self定义良好-它使编译器在声明时不再关心它。延迟声明的变量直到第一次被调用时才会被设置。因此，在这种情况下，lazy允许您在设置对象时毫无问题地使用self的概念，然后当您的对象获得.touchUpInside或.valueChanged或.addTarget()中的第三个参数时，然后它调用self的概念，在这一点上，它完全建立并完全准备成为有效的目标。所以它可以让你懒于声明你的变量。在这样的情况下，我认为他们可以给我们一个像necessary这样的关键字，但它通常被认为是一种懒惰、草率的做法，你不想在代码中到处使用它，尽管它在这种情况下可能有自己的位置。它是什么|BOLD|1864038|Swift中没有lazy+let+(常量没有lazy+)。|1864039|这是Apple+documentation+on+lazy。|1864040|这是Apple+on+variables+and+constants。在Declarations下，他们的语言参考中有更多的内容。|1864041|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html#//apple_ref/doc/uid/TP40014097-CH14-ID257|1|https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html|2|https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/doc/uid/TP40014097-CH34-ID351^0|0|A|3|0|F|I|14|8|1K|A|20|4|2J|4|3F|3|3U|4|48|4|5S|4|6C|4|6T|E|78|D|7M|C|8C|4|A9|9|1E|AT|0|0|T|8|8|M|4|0|0|U|2|R|0|0|0|1T|2|W|1|10|C|2|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|16|8|@$D|17|E|18|F|G]|$D|19|E|1A|F|G]|$D|1B|E|1C|F|G]|$D|1D|E|1E|F|G]|$D|1F|E|1G|F|G]|$D|1H|E|1I|F|G]|$D|1J|E|1K|F|G]|$D|1L|E|1M|F|G]|$D|1N|E|1O|F|G]|$D|1P|E|1Q|F|G]|$D|1R|E|1S|F|G]|$D|1T|E|1U|F|G]|$D|1V|E|1W|F|G]|$D|1X|E|1Y|F|G]|$D|1Z|E|20|F|G]|$D|21|E|22|F|J]]|9|@]|A|$]]|$1|K|3|L|5|6|7|23|8|@$D|24|E|25|F|J]|$D|26|E|27|F|G]|$D|28|E|29|F|G]]|9|@]|A|$]]|$1|M|3|N|5|6|7|2A|8|@$D|2B|E|2C|F|J]]|9|@$D|2D|E|2E|1|2F]]|A|$]]|$1|O|3|P|5|6|7|2G|8|@$D|2H|E|2I|F|J]]|9|@$D|2J|E|2K|1|2L]|$D|2M|E|2N|1|2O]]|A|$]]|$1|Q|3|-4|5|6|7|2P|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]|Y|$5|T|U|V|A|$W|Z]]|10|$5|T|U|V|A|$W|11]]]]

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 <code>let</code> 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 <code>UISegmentedControl</code>, but this also happens with <code>UIButton</code>) in its declaration when you say <code>.addTarget</code> and let the target be <code>self</code>, things crash. Why? Because <code>self</code> 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 <code>var</code>. The <code>lazy</code> fools the compiler into thinking that <code>self</code> 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, <code>lazy</code> lets you use the notion of <code>self</code> without issue while you set up the object, and then when your object gets a <code>.touchUpInside</code> or <code>.valueChanged</code> or whatever your 3rd argument is in your <code>.addTarget()</code>, THEN it calls on the notion of <code>self</code>, 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 <code>necessary</code>, 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 <code>lazy let</code> in Swift (no <code>lazy</code> for constants).

Here is the <a href="https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html#//apple_ref/doc/uid/TP40014097-CH14-ID257" rel="nofollow noreferrer">Apple documentation on lazy</a>.

Here is the <a href="https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html" rel="nofollow noreferrer">Apple on variables and constants</a>. There is a little more in their Language Reference under <a href="https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/doc/uid/TP40014097-CH34-ID351" rel="nofollow noreferrer">Declarations</a>.

blocks|key|5391666|text|尝试使用Swift+3|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5391667|button.addTarget(self,+action:#selector(ClassName.handleRegister(sender:)),+for:+.touchUpInside)|code-block|syntax|javascript|5391668|祝好运!|5391669|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Try this with Swift 3 

<pre><code>button.addTarget(self, action:#selector(ClassName.handleRegister(sender:)), for: .touchUpInside)
</code></pre>

Good luck!

blocks|key|3974194|text|尝试使用swift+3|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3974195|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)++++
}|code-block|syntax|javascript|3974196|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try with swift 3 

<pre><code>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) 
}
</code></pre>

blocks|key|1549814|text|++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)+{

++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1549815|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> 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) {

 }
</code></pre>

blocks|key|1549833|text|而不是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1549834|let+loginRegisterButton:UIButton+=+{
//...++}()|code-block|syntax|javascript|1549835|尝试：|1549836|lazy+var+loginRegisterButton:UIButton+=+{
//...++}()|1549837|这应该可以修复编译错误！|1549838|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Instead of 

<pre><code>let loginRegisterButton:UIButton = {
//... }()
</code></pre>

Try:

<pre><code>lazy var loginRegisterButton:UIButton = {
//... }()
</code></pre>

That should fix the compile error!!!

blocks|key|3974277|text|尝试使用Swift+4|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|3974278|buttonSection.addTarget(self,+action:+#selector(actionWithParam(_:)),+for:+.touchUpInside)
@objc+func+actionWithParam(sender:+UIButton){
++++//...
}

buttonSection.addTarget(self,+action:+#selector(actionWithoutParam),+for:+.touchUpInside)
@objc+func+actionWithoutParam(){
++++//...
}|code-block|syntax|javascript|3974279|entityMap^0|0|B|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Try this with Swift 4

<pre><code>buttonSection.addTarget(self, action: #selector(actionWithParam(_:)), for: .touchUpInside)
@objc func actionWithParam(sender: UIButton){
 //...
}

buttonSection.addTarget(self, action: #selector(actionWithoutParam), for: .touchUpInside)
@objc func actionWithoutParam(){
 //...
}
</code></pre>

blocks|key|3974289|text|来自Apple文档的Demo。https://developer.apple.com/documentation/swift/using_objective-c_runtime_features_in_swift|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3974290|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)
++++}
}|code-block|syntax|javascript|3974291|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/documentation/swift/using_objective-c_runtime_features_in_swift^0|F|2J|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

the Demo from Apple document. <a href="https://developer.apple.com/documentation/swift/using_objective-c_runtime_features_in_swift" rel="nofollow noreferrer">https://developer.apple.com/documentation/swift/using_objective-c_runtime_features_in_swift</a> 

<pre><code>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)
 }
}
</code></pre>

here is my <code>button</code> object 

<pre><code> 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
}()
</code></pre>

and here is my function 

<pre><code> func handleRegister(){

 FIRAuth.auth()?.createUser(withEmail: email, password: password,completion: { (user, error) in

 if error != nil
 { print("Error Occured")}

 else
 {print("Successfully Authenticated")}
 }) 
}
</code></pre>

I'm getting compile error, if addTarget removed it compiles successfully

How to use addTarget method in swift 3

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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这是我的button对象    let loginRegisterButton:UIButton = {    let button = UIButton(type: .system)    button.backgroundColor = UIColor(r: 50 , g: 80, b: 130)    butto...

问如何在swift 3中使用addTarget方法
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问如何在swift 3中使用addTarget方法EN