Referring to an NSString in output of UIAlertView?

问题

I have an NSString, testString which is set to a value in my app. Then as a response to a button press in UIAlertView I have the following code:

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 0) {
        NSLog(@"String: %@", testString);
    }
}

But for sme reason, this always causes the app to crash. I can't seem to figure out why.

回答1:

Probably you create your string with one of convenience methods and don't retain it, so when it comes to alert's clickedButtonAtIndex it's already autoreleased. You should define it as

@property (nonatomic, retain) NSString *testString;

In implementation:

@synthesize testString;

On creating:

self.testString = [NSString stringWithFormat:@"%@", @"My test string"];

and [testString release]; on dealloc.

Then when you use it in clickedButtonAtIndex you can be sure your testString has a right value

来源：https://stackoverflow.com/questions/4841399/referring-to-an-nsstring-in-output-of-uialertview