我可以在 Objective-C switch 语句中声明变量吗?

Can I declare variables inside an Objective-C switch statement?(我可以在 Objective-C switch 语句中声明变量吗?)

问题描述

我想我要瞎了，因为我不知道这段代码中的语法错误在哪里:

I think I'm going blind, because I can't figure out where the syntax error is in this code:

if( cell == nil ) {
    titledCell = [ [ [ TitledCell alloc ] initWithFrame:CGRectZero
        reuseIdentifier:CellIdentifier ] autorelease
    ];

    switch( cellNumber ) {
        case 1:
            NSString *viewDataKey = @"Name";
etc...

当我尝试编译它时，我得到一个 Error: syntax error before '*' token 在最后一行.

When I try to compile it, I'm getting an Error: syntax error before '*' token on the last line.

很抱歉问了这么一个基本问题，但我错过了什么?

Sorry for such a basic question, but what am I missing?

推荐答案

我手头没有合适的 Objective-C 编译器，但只要 C 结构相同即可:

I don't have a suitable Objective-C compiler on hand, but as long as the C constructs are identical:

switch { ... } 为您提供 一个 块级范围，而不是每个 case 一个.在作用域开头以外的任何地方声明变量都是非法的，并且在 switch 内部是特别危险的，因为它的初始化可能会被跳过.

switch { … } gives you one block-level scope, not one for each case. Declaring a variable anywhere other than the beginning of the scope is illegal, and inside a switch is especially dangerous because its initialization may be jumped over.

以下任一方法能否解决问题?

Do either of the following resolve the issue?

NSString *viewDataKey;
switch (cellNumber) {
    case 1:
        viewDataKey = @"Name";
    …
}

switch (cellNumber) {
    case 1: {
        NSString *viewDataKey = @"Name";
        …
    }
    …
}

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