NSString比较在Objective-C中不起作用

Question

以下是Objective-C代码,我试图在两个NSString值之间进行比较,但是它会引发运行时错误.这是代码:

NSDictionary *innerContent=[JSONResponseDict valueForKey:@"JSONRESPONSE"];
NSString *authFlag = [innerContent valueForKey:@"authenticationFlag"];

NSLog(@"authFlag = %@",authFlag);

UIAlertView *alert = [[UIAlertView alloc]
                      initWithTitle:nil
                      message: [NSString stringWithFormat:@"authenticationFlag = %@",authFlag]
                      delegate:self
                      cancelButtonTitle:@"OK"
                      otherButtonTitles:nil];
[alert show];
[alert release];

// This block is problematic
if ( [authFlag isEqualToString:@"1"]){
    NSLog(@"Logged in");
    self.view = homeView;
} else {
    NSLog(@"Not logged in");
}

请注意,NSString authFlag已经过测试,确实具有有效的字符串值.authFlag的值为"1"或"0"(它来自使用json-framework对JSON调用的响应).

这是运行时错误:

[Session started at 2009-03-29 19:21:00 -0700.]
2009-03-29 19:21:11.186 taggle[4144:20b] userEmail=user@domain.com&password=opensesame
2009-03-29 19:21:11.653 taggle[4144:20b] authFlag = 1
2009-03-29 19:21:11.655 taggle[4144:20b] *** -[NSCFBoolean isEqualToString:]:       unrecognized selector sent to instance 0xa089c400
2009-03-29 19:21:11.661 taggle[4144:20b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSCFBoolean isEqualToString:]: unrecognized selector sent to instance 0xa089c400'

Answer 1

正如错误日志所示,authFlag不是一个NSString,而是一个NSCFBoolean.

你可以这样做:

NSCFBoolean *authFlag = [innerContent valueForKey:@"authenticationFlag"];

if([authFlag boolValue]) {
    NSLog(@"Logged in");
    self.view = homeView;
} else {
    NSLog(@"Not logged in");
}