iOS Xcode Swift 自动完成功能坏了? [英] iOS Xcode Swift autocomplete broken?

问题描述

我没怎么用过 Swift，但我来自 Objective C，有一些关于 Swift 的东西是 PITA 来解决我的问题.

I haven't used Swift that much but coming from Objective C, there's a few things about Swift that's a PITA to get my head around.

在 iOS 编程中，我们有 animateWithDuration: 方法，它是 UIView 的一部分.

In iOS programming, we have animateWithDuration: method, which is part of UIView.

所以我尝试使用 Xcode 的自动完成并开始输入:

So I tried to use Xcode's autocomplete and begin to type:

UIView.animateWith

自动完成显示:

UIView.animateWithDuration(duration: NSTimeInterval, animations: () -> Void)

然后我切换到持续时间"字段，然后输入一个数字:

I then tabbed across to the "duration" field, and then typed in a number:

UIView.animateWithDuration(0.5, animations: () -> Void)

然后我再次切换到动画块，然后像我通常在 Objective C 中所做的那样按下 Enter，Xcode 现在显示:

Then I tabbed across again to the animation block, and pressed enter like how I normally do it in Objective C, Xcode now shows:

UIView.animateWithDuration(0.5, animations: { () -> Void in
    code
})

所以我最后一次用我的代码替换代码":

So then I tabbed one last time to replace "code" with my code:

UIView.animateWithDuration(0.5, animations: { () -> Void in
    self.customView?.transform = CGAffineTransformMakeTranslation(0.0, 0.0);
})

那时 Xcode 给了我错误:

That's when Xcode then gives me the error:

无法使用类型参数列表调用animateWithDuration"'(FloatLiteralConvertible, 动画: () -> Void)'

Cannot invoke 'animateWithDuration' with an argument list of type '(FloatLiteralConvertible, animations: () -> Void)'

我不明白.这是 Xcode 为我生成的自动完成代码，为什么它给我一个错误?

I don't understand. That's the autocomplete code that Xcode generated for me, why is it giving me an error ?

我注意到如果做一个简单的陈述:

I noticed if do a simple statement like:

UIView.animateWithDuration(0.5, animations: { () -> Void in
    var num = 1 + 1;
})

它没有给我任何错误.

大家有什么想法吗?

推荐答案

来自 "通过可选链调用方法":

任何通过可选链设置属性的尝试都会返回一个Void? 类型的值，它使您可以与 nil 进行比较以查看如果属性设置成功...

Any attempt to set a property through optional chaining returns a value of type Void?, which enables you to compare against nil to see if the property was set successfully ...

因此表达式的类型

self.customView?.transform = CGAffineTransformMakeTranslation(0.0, 0.0)

是Void?(可选的Void).如果一个闭包只包含一个单个表达式，那么这个表达式会自动作为返回值.错误信息相当具有误导性，但它来自于 Void? 是不同于Void.

is Void? (optional Void). And if a closure consists only of a single expression, then this expression is automatically taken as the return value. The error message is quite misleading, but it comes from the fact that Void? is different from Void.

添加一个显式的return语句即可解决问题:

Adding an explicit return statement solves the problem:

UIView.animateWithDuration(0.5, animations: { () -> Void in
    self.customView?.transform = CGAffineTransformMakeTranslation(0.0, 0.0)
    return
})

更新: 添加一个明确的 return 语句是不必要的不再使用 Swift 1.2 (Xcode 6.3).来自 Beta 版发行说明:

Update: Adding an explicit return statement it not necessary anymore with Swift 1.2 (Xcode 6.3). From the beta release notes:

具有非 Void 返回类型的未注释的单表达式闭包现在可以在 Void 上下文中使用.

Unannotated single-expression closures with non-Void return types can now be used in Void contexts.

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