前言

在Swift3.1中使用initialize会出现如下警告：

Method 'initialize()' defines Objective-C class method 'initialize', which is not guaranteed to be invoked by Swift and will be disallowed in future versions。

以下是国外论坛上的一种方案：

1.

Define the following Swift code. The purpose is to provide a simple entry point for any class that you would like to imbue with behaviour akin to initialize() - this can now be done simply by conforming to SelfAware. It also provides a single function to run this behaviour for every conforming class.

/// 定义 `protocol`
public protocol SelfAware: class {
    static func awake()
}

// 创建代理执行单例
class NothingToSeeHere{

    static func harmlessFunction(){
        let typeCount = Int(objc_getClassList(nil, 0))
        let  types = UnsafeMutablePointer<AnyClass?>.allocate(capacity: typeCount)
        let autoreleaseintTypes = AutoreleasingUnsafeMutablePointer<AnyClass?>(types)
        objc_getClassList(autoreleaseintTypes, Int32(typeCount)) //获取所有的类
        for index in 0 ..< typeCount{
            (types[index] as? SelfAware.Type)?.awake() //如果该类实现了SelfAware协议，那么调用awake方法
        }
        types.deallocate(capacity: typeCount)
    }
}

2.

That’s all good and well, but we still need a way to actually run the function we defined, i.e. NothingToSeeHere.harmlessFunction(), on application start up. Previously, this answer suggested using Objective-C code to do this. However, it seems that we can do what we need using only Swift. For macOS or other platforms where UIApplication is not available, a variation of the following will be needed.

/// 执行单例
extension UIApplication {
    private static let runOnce:Void = {
        //使用静态属性以保证只调用一次(该属性是个方法)
        NothingToSeeHere.harmlessFunction()
        UIButton.harmlessFunction()
    }()

    open override var next: UIResponder?{
        UIApplication.runOnce
        return super.next
    }
}

3.

We now have an entry point at application start up, and a way to hook into this from classes of your choice. All that is left to do: instead of implementing initialize(), conform to SelfAware and implement the defined method, awake().

/// 将类设置为代理并在代理中实现运行时代吗
extension UIButton:SelfAware{
    public static func awake() {
        
    }
}

参考