"初始化" Swift中类的类方法？ [英] "initialize" class method for classes in Swift?

问题描述

我正在寻找类似于Objective-C的 +（void）initialize 类方法的行为，因为该方法在初始化类时被调用一次，而且从不此后再次。

I'm looking for behavior similar to Objective-C's +(void)initialize class method, in that the method is called once when the class is initialized, and never again thereafter.

类中的简单类init（）{} 关闭会非常时尚！显然，当我们在结构闭包中使用 class var s而不是 static var s时，这一切都很好！

A simple class init () {} in a class closure would be really sleek! And obviously when we get to use "class vars" instead of "static vars in a struct closure", this will all match really well!

推荐答案

如果你有一个Objective-C类，最简单的就是覆盖 +初始化。但是，请确保您班级的子类还覆盖 + initialize ，否则您的班级 + initialize 可能不止一次被召唤！如果需要，您可以使用 dispatch_once（）（如下所述）来防止多次通话。

If you have an Objective-C class, it's easiest to just override +initialize. However, make sure subclasses of your class also override +initialize or else your class's +initialize may get called more than once! If you want, you can use dispatch_once() (mentioned below) to safeguard against multiple calls.

class MyView : UIView {
  override class func initialize () {
    // Do stuff
  }
}

 

如果你有Swift课程，你可以获得的最好成绩是 dispatch_once（）在 init（）语句中。

If you have a Swift class, the best you can get is dispatch_once() inside the init() statement.

private var once = dispatch_once_t()

class MyObject {
  init () {
    dispatch_once(&once) {
      // Do stuff
    }
  }
}

这个解决方案不同于 + initialize （这是第一次对Objective-C类进行消息调用），因此不是问题的真正答案。但它足够好，IMO。

This solution differs from +initialize (which is called the first time an Objective-C class is messaged) and thus isn't a true answer to the question. But it works good enough, IMO.

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