是否可以允许在 Swift 初始化期间调用 didSet? [英] Is it possible to allow didSet to be called during initialization in Swift?

问题描述

问题

Apple 的文档 指定:

<块引用>

willSet 和 didSet 观察者在属性第一次初始化时不会被调用.仅当属性的值设置在初始化上下文之外时才会调用它们.

是否可以在初始化期间强制调用这些?

为什么?

假设我有这门课

class SomeClass {var someProperty: AnyObject {已设置{做东西()}}init(someProperty: AnyObject) {self.someProperty = someProperty做东西()}func doStuff() {//既然设置了 someProperty 就做一些事情}}

我创建了方法 doStuff，以使处理调用更加简洁，但我宁愿只处理 didSet 函数中的属性.有没有办法在初始化期间强制调用它?

更新

我决定为我的类移除便利的初始化器，并强制您在初始化后设置该属性.这让我知道 didSet 将始终被调用.我还没有决定这是否总体上更好，但它很适合我的情况.

解决方案

创建自己的 set-Method 并在您的 init-Method 中使用它:

class SomeClass {var someProperty: AnyObject!{已设置{//做一些事情}}init(someProperty: AnyObject) {setSomeProperty(someProperty)}func setSomeProperty(newValue:AnyObject) {self.someProperty = newValue}}

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通过将 someProperty 声明为类型:AnyObject!(一个隐式的解包可选)，您允许 self 完全初始化而无需someProperty 正在设置.你打电话时setSomeProperty(someProperty) 你正在调用相当于self.setSomeProperty(someProperty).通常你不能这样做是因为 self 尚未完全初始化.自从someProperty 不需要初始化，您正在调用方法依赖于 self，Swift 离开初始化上下文并didSet 将运行.

Question

Apple's docs specify that:

willSet and didSet observers are not called when a property is first initialized. They are only called when the property’s value is set outside of an initialization context.

Is it possible to force these to be called during initialization?

Why?

Let's say I have this class

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

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

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

I created the method doStuff, to make the processing calls more concise, but I'd rather just process the property within the didSet function. Is there a way to force this to call during initialization?

Update

I decided to just remove the convenience intializer for my class and force you to set the property after initialization. This allows me to know didSet will always be called. I haven't decided if this is better overall, but it suits my situation well.

解决方案

Create an own set-Method and use it within your init-Method:

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.

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