是否有必要在将一个字符串与另一个变量进行比较之前将其赋值给该变量？

我想将 NSString的值与字符串“错误”进行比较，下面是我的代码:

NSString *wrongTxt = [[NSString alloc] initWithFormat:@"Wrong"];
if( [statusString isEqualToString:wrongTxt] ){
doSomething;
}

我真的需要为“错误”创建 NSString 吗？

此外，我可以比较一个 UILabel的 text的值到一个字符串没有分配标签值到一个字符串？

107754 次浏览
小开 
if ([statusString isEqualToString:@"Wrong"]) {
// do something
}
小开
最佳答案

Do I really have to create an NSString for "Wrong"?

No, why not just do:

if([statusString isEqualToString:@"Wrong"]){
//doSomething;
}

Using @"" simply creates a string literal, which is a valid NSString.

Also, can I compare the value of a UILabel.text to a string without assigning the label value to a string?

Yes, you can do something like:

UILabel *label = ...;
if([someString isEqualToString:label.text]) {
// Do stuff here
}
小开

Brian, also worth throwing in here - the others are of course correct that you don't need to declare a string variable. However, next time you want to declare a string you don't need to do the following:

NSString *myString = [[NSString alloc] initWithFormat:@"SomeText"];

Although the above does work, it provides a retained NSString variable which you will then need to explicitly release after you've finished using it.

Next time you want a string variable you can use the "@" symbol in a much more convenient way:

NSString *myString = @"SomeText";

This will be autoreleased when you've finished with it so you'll avoid memory leaks too...

Hope that helps!

小开

You can also use the NSString class methods which will also create an autoreleased instance and have more options like string formatting:

NSString *myString = [NSString stringWithString:@"abc"];
NSString *myString = [NSString stringWithFormat:@"abc %d efg", 42];

提交答案