我也有同样的问题，这个方法对我很有效

class SomeClass {
    var someProperty: AnyObject {
        didSet {
            doStuff()
        }
    }

    init(someProperty: AnyObject) {
        defer { self.someProperty = someProperty }
    }

    func doStuff() {
        // do stuff now that someProperty is set
    }
}

在特定的情况下，你想在init中调用willSet或didSet来获取父类中可用的属性，你可以简单地直接分配你的父属性:

override init(frame: CGRect) {
    super.init(frame: frame)
    // this will call `willSet` and `didSet`
    someProperty = super.someProperty
}

注意，带闭包的Charlesism解决方案在这种情况下也总是有效的。所以我的解只是一种选择。

创建一个自己的set-Method，并在init-Method中使用它:

class SomeClass {
    var someProperty: AnyObject! {
        didSet {
            //do some Stuff
        }
    }

    init(someProperty: AnyObject) {
        setSomeProperty(someProperty)
    }

    func setSomeProperty(newValue:AnyObject) {
        self.someProperty = newValue
    }
}

By declaring someProperty as type: AnyObject! (an implicitly unwrapped optional), you allow self to fully initialize without someProperty being set. When you call setSomeProperty(someProperty) you're calling an equivalent of self.setSomeProperty(someProperty). Normally you wouldn't be able to do this because self hasn't been fully initialized. Since someProperty doesn't require initialization and you are calling a method dependent on self, Swift leaves the initialization context and didSet will run.

不幸的是，根类初始化时不会调用didSet观察器。

如果你的类不是子类，你必须使用getter和setter来实现你想要的功能:

class SomeClass {
    private var _test: Int = 0
    var test: Int {
        get { _test }
        set { _test = newValue }
    }
    
    init(test: Int) { self.test = test }
}

或者，如果你的类是一个子类，你可以使用didSet并执行:

override init(test: int) {
    super.init()
    self.test = test
}

在super.init()被调用之后，didSet应该被调用。

有一件事我没有尝试过，但可能也有用:

init(test: int) {
    defer { self.test = test }
}

注意:你需要让你的属性为空，或者为它们设置一个默认值，或者打开类属性。

作为Oliver回答的一种变体，您可以将这些行包装成闭包。例如:

class Classy {

    var foo: Int! { didSet { doStuff() } }

    init( foo: Int ) {
        // closure invokes didSet
        ({ self.foo = foo })()
    }

}

编辑:Brian Westphal的回答更好。这句话的好处是暗示了他的意图。

你可以用obj-с的方法来解决:

class SomeClass {
    private var _someProperty: AnyObject!
    var someProperty: AnyObject{
        get{
            return _someProperty
        }
        set{
            _someProperty = newValue
            doStuff()
        }
    }
    init(someProperty: AnyObject) {
        self.someProperty = someProperty
        doStuff()
    }

    func doStuff() {
        // do stuff now that someProperty is set
    }
}