类未实现其超类的必需成员 [英] Class does not implement its superclass's required members

问题描述

所以我今天更新到 Xcode 6 beta 5，发现我在 Apple 类的几乎所有子类中都收到了错误.

So I updated to Xcode 6 beta 5 today and noticed I received errors in nearly all of my subclasses of Apple's classes.

错误状态:

类x"未实现其超类所需的成员

Class 'x' does not implement its superclass's required members

这是我选择的一个例子，因为这个类目前非常轻量级，所以很容易发布.

Here is one example I picked because this class is currently pretty lightweight so it will be easy to post.

class InfoBar: SKSpriteNode  { //Error message here

    let team: Team
    let healthBar: SKSpriteNode

    init(team: Team, size: CGSize) {
        self.team = team
        if self.team == Team.TeamGood {
            healthBar = SKSpriteNode(color: UIColor.greenColor(), size:size)
        }
        else {
            healthBar = SKSpriteNode(color: UIColor.redColor(), size:size)
        }
        super.init(texture:nil, color: UIColor.darkGrayColor(), size: size)

        self.addChild(healthBar)

    }

}

所以我的问题是，为什么我会收到此错误，我该如何解决?我没有执行什么?我正在调用指定的初始化程序.

So my question is, why am I receiving this error, and how can I fix it? What is it that I am not implementing? I'm calling a designated initializer.

推荐答案

来自开发者论坛上的 Apple 员工:

From an Apple employee on the Developer Forums:

"向编译器和构建的程序声明你真正不想与 NSCoding 兼容就是做这样的事情:"

"A way to declare to the compiler and the built program that you really don't want to be NSCoding-compatible is to do something like this:"

required init(coder: NSCoder) {
  fatalError("NSCoding not supported")
}

如果您知道自己不想遵守 NSCoding，这是一个选项.我的很多 SpriteKit 代码都采用了这种方法，因为我知道我不会从情节提要中加载它.

If you know you don't want to be NSCoding compliant, this is an option. I've taken this approach with a lot of my SpriteKit code, as I know I won't be loading it from a storyboard.

您可以采用的另一个效果很好的选项是将方法实现为便利 init，如下所示:

Another option you can take which works rather well is to implement the method as a convenience init, like so:

convenience required init(coder: NSCoder) {
    self.init(stringParam: "", intParam: 5)
}

注意 self 中对初始化程序的调用.这允许您只需要对参数使用虚拟值，而不是所有非可选属性，同时避免引发致命错误.

Note the call to an initializer in self. This allows you to only have to use dummy values for the parameters, as opposed to all non-optional properties, while avoiding throwing a fatal error.

第三个选项当然是在调用 super 时实现该方法，并初始化所有非可选属性.如果对象是从故事板加载的视图，您应该采用这种方法:

The third option of course is to implement the method while calling super, and initialize all of your non-optional properties. You should take this approach if the object is a view being loaded from a storyboard:

required init(coder aDecoder: NSCoder!) {
    foo = "some string"
    bar = 9001

    super.init(coder: aDecoder)
}

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