Xcode 7.3 / Swift 2:“没有使用Objective-C选择器声明的方法”警告

I've been using selectors for a while, and even after migrating to Swift I was able to use them without issues. That's how I was using on Swift 2 without issues until I updated Xcode to version 7.3:

我使用选择器已经有一段时间了，甚至在迁移到Swift之后，我也可以毫无问题地使用它们。这就是我使用Swift 2的方式，直到我将Xcode更新为7.3版:

As use can see I use selectors with NSTimer.

可以看到，我使用了选择器和NSTimer。

This is the action that is called:

这就是所谓的行动:

 func Start () {

 }

As you can see Xcode 7.3 now gives a warning "No method declared with Objective-C selector". By clicking on the warning, Xcode offers a quick fix to the code by adding "Selector", but then I still get the same warning:

如您所见，Xcode 7.3现在给出了一个警告“没有使用Objective-C选择器声明的方法”。通过单击警告，Xcode通过添加“Selector”对代码进行了快速修复，但我仍然得到相同的警告:

4 个解决方案

#1

Since Swift 2.2 / Xcode 7.3 there is a new way to use a selector: Selector("funcName") was changed to #selector(ClassName.funcName)

由于Swift 2.2 / Xcode 7.3，有一种新的方法可以使用selector: selector(“funcName”)被更改为#selector(ClassName.funcName)

Have a look at https://github.com/apple/swift-evolution/blob/master/proposals/0022-objc-selectors.md ,

看看https://github.com/apple/swift-演进/ blob/master/sals/0022 - objectors.md，

tl;dr;

tl,博士;

Replace Selector("Start") with #selector(YOUR_CLASS.Start)

替代选择器(“开始”)#选择器(YOUR_CLASS.Start)

where YOUR_CLASS = class of target in given context.

其中YOUR_CLASS =目标的类。

If you don't want to do it manually, Xcode provides easy fix itself by default, when you have the following situation, tap on the Yellow triangles ( sometimes required to tap/click multiple times ),

如果您不想手工操作，Xcode默认提供了简单的修复，当您有以下情况时，点击黄色三角形(有时需要多次点击)，

it will give you suggestion:

它会给你建议:

And if you select that suggestion, it will automatically update the selector:

如果你选择那个建议，它会自动更新选择器:

#2

Both following statements work perfectly. The upper one is mostly used. However when the selector method is in a different ViewController the compiler warning "No method declared with Objective-C selector 'buttonHandler'" may occur.

以下两种说法都很有效。上面的部分大部分是用的。但是，当选择器方法位于不同的ViewController中时，编译器会发出警告，“不会出现使用Objective-C选择器'buttonHandler'声明的方法”。

The second listed statement does not give this warning.

第二个列出的语句没有给出这个警告。

button.addTarget(parentViewController, action: Selector("buttonHandler:"), forControlEvents: .TouchUpInside)

button.addTarget(parentViewController, action: #selector(MainViewController.buttonHandler), forControlEvents: .TouchUpInside)

In the target view controller (MainViewController) you can define the module:

在目标视图控制器(MainViewController)中，您可以定义模块:

func buttonHandler(sender:UIButton!) {
    print ("Pressed")
}

#3

On Swift 4 I had to add @objc before the func to get rid of the warnings.

在Swift 4上，我必须在func之前添加@objc以消除警告。

This is how I call the func with NSTimer:

我用NSTimer这样称呼func:

 Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(ViewController.intro), userInfo: nil, repeats: false)

This is how the func is declared:

以下是基金会的声明:

     @objc func intro () {

          // do your stuff here         

     }

I also updated the setting as the Xcode requested:

我还按照Xcode的要求更新了设置:

No more warnings, everything seems to be working fine.

没有更多的警告，一切似乎都很顺利。

#4

Some findings of my own to support what Vincent said (too long to be a direct comment)

我自己的一些发现支持文森特所说的话(太长了不能直接评论)

It's not necessarily in a different view controller, but just a different file where the following format won't work:

它不一定是在不同的视图控制器中，而是在不同的文件中，以下格式不能工作:

button.addTarget(parentViewController, action: Selector("buttonHandler:"), forControlEvents: .TouchUpInside)

按钮。addTarget(parentViewController, action: Selector(“buttonHandler:”)，forControlEvents: .TouchUpInside)

For instance, if you have an extension in a separate file, although for the same view controller, this format Selector("buttonHandler:") won't work.

例如，如果在一个单独的文件中有一个扩展，尽管对于相同的视图控制器，这个格式选择器(“buttonHandler:”)不能工作。

Further, when the selector is in the same file and VC, Xcode's quick-fix prompts you to have the selector include the constructor, so it would look something like this:

此外，当选择器位于相同的文件和VC中时，Xcode的快速修复会提示您让选择器包含构造函数，所以它看起来是这样的:

#selector(MainViewController.buttonHandler(_:))

#选择器(MainViewController.buttonHandler(_)):

However this format only works when the selector is in the same VC + file, if it is in a separate file, but same VC, then that recommended method won't work, and you need to use the method without the constructor

但是，这种格式只在选择器位于相同的VC +文件中时才有效，如果选择器位于单独的文件中，但是在相同的VC中，那么推荐的方法将不起作用，您需要使用没有构造函数的方法

#selector(MainViewController.buttonHandler)

#选择器(MainViewController.buttonHandler)

#1