点击时更改按钮的文本颜色

I'm trying to get a button's text to change font color to red when tapped. I looked at similar posts from months ago and use of that code causes a build error in Xcode 6.1.1. Here is the code I'm trying:

我试图获取一个按钮的文本，在点击时将字体颜色更改为红色。我查看了几个月前的类似帖子，使用该代码会导致Xcode 6.1.1中出现构建错误。这是我正在尝试的代码：

class ViewController: UIViewController {

    @IBAction func firstButton(sender: UIButton) { 
        firstButton.titleLabel.textColor = UIColor.redColor()
    }
}

The error code that I get is:

我得到的错误代码是：

'(UIButton) -> ()' does not have a member named 'titleLabel'

'（UIButton） - >（）'没有名为'titleLabel'的成员

Any help will be much appreciated as I see Swift as my saving grace after having lost patience in trying to learn Objective C.

任何帮助将非常感激，因为我在尝试学习Objective C后失去耐心，因此我认为Swift是我的拯救恩典。

4 个解决方案

#1

You're trying to change the text color of the function's titleLabel, which doesn't make sense. You should be accessing sender parameter instead if you're trying to get a reference to the button to get at its titleLabel. Additionally, as rakeshbs points out, titleLabel is an optional property of UIButton.

您正在尝试更改函数titleLabel的文本颜色，这没有意义。如果您尝试获取对按钮的引用以获取其titleLabel，则应该访问sender参数。另外，正如rakeshbs指出的那样，titleLabel是UIButton的可选属性。

class ViewController: UIViewController {

    @IBAction func firstButton(sender: UIButton) {
        sender.titleLabel?.textColor  = UIColor.redColor()
    }
}

If you break down your error message, you'll realize that this is clearly the issue.

如果你打破错误信息，你会发现这显然是个问题。

'(UIButton) -> ()' does not have a member named 'titleLabel'

'（UIButton） - >（）'没有名为'titleLabel'的成员

Which states that you are trying to access a member (or property) named titleLabel on an object of type (UIButton) -> (), which means a function that takes a button as input and returns nothing.

这表明您试图在类型（UIButton） - >（）的对象*问名为titleLabel的成员（或属性），这意味着一个函数将按钮作为输入并且不返回任何内容。

#2

For anyone interested in the exact swift code necessary to make this question of mine work, here it is:

对于任何对使我的工作问题所需的确切快速代码感兴趣的人，这里是：

class ViewController: UIViewController {

@IBAction func firstButton(sender: UIButton) {

    sender.setTitleColor(UIColor.redColor(), forState: UIControlState.Normal)

}

#3

this will work for Swift 3 :

这适用于Swift 3：

yourButton.setTitleColor(UIColor.blue, for: .normal)

yourButton.setTitleColor（UIColor.blue，for：。normal）

#4

UIButton.titlelabel is an optional property. You have to use optional chaining for changing its properties.

UIButton.titlelabel是一个可选属性。您必须使用可选链接来更改其属性。

firstButton.titleLabel?.backgroundColor = UIColor.redColor()

Please read about swift optionals to understand this in detail. http://www.appcoda.com/beginners-guide-optionals-swift/

请阅读有关swift选项的详细信息。 http://www.appcoda.com/beginners-guide-optionals-swift/