编译错误：开关，“期望的表达式之前” [英] Compile Error with: switch, "expected expression before"

问题描述

切换到追逐我已经重新创建我的问题，因为它是相当自我解释。

Cut to the chase I have recreated my problem as it is fairly self explanatory.

此操作正确无误：

switch (n) {
    case 1:
        NSLog(@"");
        NSString *aStr;
        break;
    default:
        break;
    }

此编译错误 NSLog（）：

switch (n) {
    case 1:
        NSString *aStr;
        break;
    default:
        break;
    }

它会在编译时抛出一个错误

it throws an error at compile "Expected expression before 'NSString'"

我在这里缺少什么？

推荐答案

在正常的C中，在两种情况下都必须用括号括起来。我怀疑这可能解决您的问题：

In normal C you'd have to enclose this in brackets in both cases. I suspect this may fix your problem:

case 1:
{
    NSLog(@"");
    NSString *aStr;
    break;
}

查看

See this SO question for more info.

另一种方法是使用下面的命令：解决这个问题是在case标签和第一个声明之间放置一个语句，就像你在上面的工作示例中做的那样。有关详情，请参阅评论和Quinn Taylor的回答。

Another way to get around this problem is to put a statement between the case label and the first declaration as you've done in your working example above. See the comments and Quinn Taylor's answer for more info.

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