Xcode Swift 编译器警告永远不会执行

Xcode Swift compiler warning will never be executed

提问by Dribbler

I have code in this vein:

我有这样的代码：

enum enumThingType {
    case apples
    case oranges
    case starfruit
}

func myFunc( enumThing: enumThingType ) -> String {
    switch enumThing {
    case .apples:
        return "Hey, apples"
    case .oranges:
        return "Hey, oranges"        
    default:
        return ""
    }
}

I'm very slowly filling in the code for all of the cases, and I have need of the code to be functional while I code for starfruitand its ilk.

我正在非常缓慢地为所有情况填写代码，并且在我为杨桃及其同类代码编写代码时，我需要代码具有功能性。

All is good, but the compiler issues the warning will never be executedfor return "". It happily generates an executable, but I am compulsive and would like warnings and errors to go away.

一切都很好，但编译器发出警告，永远不会为return "". 它很高兴地生成了一个可执行文件，但我是强制性的，希望警告和错误消失。

If I delete the line return "", then I get the very real and compiler arresting Missing return in a function expected to return 'String'.

如果我删除该行return ""，那么我会在预期返回 'String' 的函数中得到非常真实的编译器捕获Missing 返回。

Likewise, if I just delete default:..., I get the equally arresting error Switch must be exhaustive, consider adding a default clause, which is fully understandable, but I am creative in my efforts to thwart warnings and errors.

同样，如果我只是删除default:...，我会得到同样引人注目的错误Switch must be extinctive，考虑添加一个 default clause，这是完全可以理解的，但我在努力阻止警告和错误方面很有创意。

So given this construct, can I eliminate warnings and errors while still coding for existing cases for myFunc?

因此，鉴于此构造，我是否可以消除警告和错误，同时仍然为 的现有案例编码myFunc？

EDIT

编辑

As @appzYourLife pointed out, I omitted precompiler directives in my sample code that were creating the error. This code, with the precompiler directives, throws a warning:

正如@appzYourLife 指出的那样，我在示例代码中省略了导致错误的预编译器指令。此代码带有预编译器指令，会引发警告：

enum enumThingType {
    case apples
    case oranges
    case starfruit
}

func myFunc( enumThing: enumThingType ) -> String {
    switch enumThing {
    case .apples:
        return "Hey, apples"
    case .oranges:
        return "Hey, oranges"        
    default:
    #if DEBUG
        print( "Ouch!" )
    #else
        fatalError()
    #endif
        return ""
    }
}

Because if the product is not created with DEBUG specified, then return can never happen--the FatalError()prevents that.

因为如果产品不是在指定 DEBUG 的情况下创建的，那么返回永远不会发生——这会FatalError()阻止这种情况。

This code, however, does notthrow a warning for all precompiler specified cases:

但是，此代码不会对所有预编译器指定的情况发出警告：

func myFunc( enumThing: enumThingType ) -> String {
    switch enumThing {
    case .apples:
        return "Hey, apples"
    case .oranges:
        return "Hey, oranges"        
    default:
    #if DEBUG
        print( "Ouch!" )
        return ""
    #else
        fatalError()
    #endif
    }
}

I just wanted to summarize the actual code fix for anyone who might gander across this, as the lack of a properly specified DEBUG flag fixed it for a DEBUG condition, but not for a non DEBUG condition. Thanks again for everyone who helped on this!

我只是想为任何可能对此感到困惑的人总结实际的代码修复，因为缺少正确指定的 DEBUG 标志将其修复为 DEBUG 条件，而不是非 DEBUG 条件。再次感谢所有为此提供帮助的人！

采纳答案by Luca Angeletti

I follow the chat you had with @matt, so it looks like the code you posted in your question was NOTthe real code ;)

我关注了你与@matt的聊天，所以看起来你在问题中发布的代码不是真正的代码；)

The real code is more something like this

真正的代码更像这样

func myFunc( enumThing: enumThingType ) -> String {
    switch enumThing {
    case .apples:
        return "Hey, apples"
    case .oranges:
        return "Hey, oranges"
    default:
        #if DEBUG
        print("...")
        #else
        fatalError()
        #endif
        return ""
    }
}

Now I am getting your warning and it is totally correct.

现在我收到了你的警告，这是完全正确的。

In fact since DEBUGis NOTdefined, the #elseblock will be executed.

事实上，因为DEBUG被NOT定义的，#else块将被执行。

So the fatalError()will be executed.

所以fatalError()会被执行。

And since you are putting a return ""immediately after a fatalError()... well the returnof course will never be executed.

并且由于您在 areturn ""之后立即放置了fatalError()...return当然永远不会被执行。

The compiler is right.

编译器是对的。

Update: defining the DEBUG complier flag

更新：定义 DEBUG 编译器标志

1. Open the project root
2. Select your target
3. Look for the Swift Compiler - Custom Flagssection
4. Add to debug or release this entry: -D DEBUG

1. 打开项目根目录
2. 选择你的目标
3. 寻找Swift Compiler - Custom Flags栏目
4. 添加以调试或发布此条目： -D DEBUG