ios Objective-C Switch 语句
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Objective-C Switch Statement
提问by Echilon
Possible Duplicate:
Declaring variables inside a switch statement
可能的重复：
在 switch 语句中声明变量
I'm having difficulty getting XCode to let me write a particular switch statement in Objective-C. I'm famiiar with the syntax and could rewrite it as if/else blocks but I'm curious.
我很难让 XCode 允许我在 Objective-C 中编写特定的 switch 语句。我熟悉语法，可以将它重写为 if/else 块，但我很好奇。
switch (textField.tag) {
case kComment:
ingredient.comment = textField.text;
break;
case kQuantity:
NSLog(@""); // removing this line causes a compiler error
NSNumberFormatter *fmt = [[NSNumberFormatter alloc] init];
fmt.generatesDecimalNumbers = true;
NSNumber *quantity = [fmt numberFromString:textField.text];
[fmt release];
ingredient.quantity = quantity;
break;
}
I can't see the syntax error, it's as though I need to trick the compiler into allowing this.
我看不到语法错误，就好像我需要欺骗编译器允许这样做一样。
回答by Michael Krelin - hacker
You can not add variable declaration after the label. You can add a semicolon instead of call to NSLog()for instance. Or declare variable before the switch. Or add another {}.
不能在标签后添加变量声明。例如，您可以添加分号而不是调用NSLog()。或者在 switch 之前声明变量。或添加另一个{}.
回答by iCreative
Remove the variable declaration part within the switch statement.
删除 switch 语句中的变量声明部分。
Within switch statement you can't create any variable in Objective-C.
在 switch 语句中，你不能在 Objective-C 中创建任何变量。
NSNumberFormatter *fmt = nil;
NSNumber *quantity = nil;
switch (textField.tag) {
case kComment:
ingredient.comment = textField.text;
break;
case kQuantity:
fmt = [[NSNumberFormatter alloc] init];
fmt.generatesDecimalNumbers = true;
quantity = [fmt numberFromString:textField.text];
[fmt release];
ingredient.quantity = quantity;
break;
}
Try this...
尝试这个...
