在swift中覆盖属性 [英] Overriding properties in swift

问题描述

例如a有第一个类

public class MyBaseButton: UIButton {

    public var weight: Double = 1.0

    public var text: String? {
        get {
            return self.titleForState(.Normal)
        }
        set {
            return self.setTitle(newValue, forState: .Normal)
        }
    }
}

继承类：

public class SomeButton: SomeBaseButton {

    override public var text: String? = "text"
    override public var weight: Double = 2.0
}

所以，逻辑是 SomeClass 定义自己的文本和权重。
但是我收到错误：

So, the logic is that SomeClass define own text and weight. But I'm getting an errors:

对于文字：无法覆盖存储的属性'text'

对于重量：无法覆盖存储的属性'权重'

推荐答案

有趣的是，这在纯Swift类中效果很好。例如，这可以按预期工作：

Interestingly this works just fine in pure Swift classes. For example, this works as expected:

public class FooButton {
    public var weight: Double = 1.0
}

public class BarButton: FooButton {
    override public var weight: Double = 2.0
}

它不适合你的原因是因为你正在使用Objective-C类：因为 UIButton 是一个目标 - C类，它的所有子类也都是。因此，规则似乎有点不同。

The reason it does not work for you is because you are working with Objective-C classes: since UIButton is an Objective-C class, all its subclasses will be too. Because of that, the rules seem to be a bit different.

Xcode 6.3实际上提供了更多信息。它显示以下两个错误：

Xcode 6.3 is actually a bit more informative. It shows the following two errors:

getter forweight覆盖Objective-C方法weight来自超类FooButton
权重的设定者覆盖Objective-C方法setWeight：来自超类Foobutton

Getter for "weight" overrides Objective-C method "weight" from superclass "FooButton" Setter for "weight" overrides Objective-C method "setWeight:" from superclass "Foobutton"

由于以下方法有效... 。

Since the following does work ...

public class BarButton: FooButton {
    override public var weight: Double {
        get {
            return 2.0
        }
        set {
            // Do Nothing
        }
    }
}

...我的猜测是这些方法根本没有正确合成。

... my guess is that these methods are simply not synthesized correctly.

我想知道是否这是编译器错误。或者是一个缺点。因为我认为可以处理这个案子。

I wonder if this is a compiler bug. Or a shortcoming. Because I think it could handle the case.

也许Swift设计师认为如果重写权重您也可以在初始化程序中将其设置为不同的值。嗯。

Maybe the Swift designers thought that in case of overriding weight you could also simply set it to a different value in your initializer. Hm.

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