xcode 4 - 简单代码不工作？ [英] xcode 4 - Simple code not working?

问题描述

这是我的代码

this is my code

//set button cliekd
- (IBAction)SetBtn:(id)sender {
     NSString *formattedDateString = [_dateformatter stringFromDate:_datepicker.dateValue];
    _settimelabel.stringValue = formattedDateString;
}


//timer ticking
-(void) onTick {
    _formattedDateString = [_dateformatter stringFromDate:[NSDate date]];
   _thetimelabel.stringValue =_formattedDateString;

    if (_thetimelabel.stringValue == _settimelabel.stringValue ) {

        if (_messageCheckBox.state == 1)
        {
            //show notification
            NSUserNotification *notification = [[NSUserNotification alloc] init];
            notification.title = @"FastAlarmClock: Alert!";
            notification.informativeText = _textfeild.stringValue;
            notification.soundName = NSUserNotificationDefaultSoundName;

            [[NSUserNotificationCenter defaultUserNotificationCenter] deliverNotification:notification];
        }

        //play the alarm
        NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Alarm" ofType:@"mp3"];
        NSURL* file = [[NSURL alloc] initFileURLWithPath:filePath];
        audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:file error:nil];
        [audioPlayer prepareToPlay];

        [audioPlayer play];

    }

错误发生在

the error is at

if (_thetimelabel.stringValue == _settimelabel.stringValue ) {

他们都是标签，他们最终都是成熟的，这是一个闹钟，我不明白为什么它不解雇，有人可以解释一下吗？我明白了！就像lol=lol做某事一样。 imm so confused

they are both labels, they both end up matcing, this is an alarm clock, i don''t understand why its not firing, can some one please explain? I do understand! its like if "lol" = "lol" do something. imm so confused

推荐答案

通过测试两个字符串是==你实际上是在询问变量指向的对象是否是同一个对象。



我猜他们不是。



您需要检查这些对象的字符串值是否相等

By testing for the two strings being == you are actually asking whether the objects pointed to by the variables are the same object.

And I guess they''re not.

You need to check if the string values of those objects are equal

if ([_thetimelabel.stringValue isEqualTostring:_settimelabel.stringValue] ) {

当你使用常数时

When you use constants

NSString* myVar1 = @"foo";
NSString* myVar2 = @"foo";

然后myVar1 == myVar2为真 - 但只有因为编译器发现两个常量相同，因此引用相同的对象。当你有两个具有值的NSString *时，它们（通常是！）将指向完全不同的对象，因此不相等。

then myVar1 == myVar2 is true - but onlyh because the compiler spots that the two constants are the same, and so references the same object. When you have two NSString* that have values, they (usually!) will point to completely different objects, and so are not equal.

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