NSString属性在IBAction方法中失去了值

Question

我有一个NSString属性self。textFromTextVC，在Viewcontroller中，它的值在IBAction方法中变为null。

- (IBAction)buttonPressed:(id)sender
{
    NSLog(@"text before alarm is created: %@", self.textFromTextVC);
}

下面的方法是相同的。

-(void)setPropertyTextToReceivedText:(NSString *)text
{
    self.textFromTextVC = text;
    NSLog(@"text received from text VC: %@", self.textFromTextVC);
    [self doesStringKeepValue]; //I call this method to check and see if the NSString value     
                                //was retained
}
-(void)doesStringKeepValue
{
    NSLog(@"keep value: %@", self.textFromTextVC); //NSString value the same from the above
                                                   //method
}

下面是我如何声明NSString属性的:

@property (nonatomic, copy) NSString *textFromTextVC;

基本上，我在IBAction方法被调用之前设置了self.textFromTextVC，这就是为什么我感到困惑。我真的不知道发生了什么事。我选择了ARC。我希望我只是犯了个小错误……救命?谢谢你,

下面是另一个视图控制器中的方法，我调用setPropertyTextToReceivedText:

@implementation TextViewController
@synthesize typedText;

- (IBAction)doneButton:(id)sender {
    [self.typedText resignFirstResponder];
    AlarmViewController *receiver = [[AlarmViewController alloc]init];
    [receiver setPropertyTextToReceivedText:self.typedText.text];
    //[self showAlert];
}

Answer 1

您的问题是receiver与显示(当前/已推送)的VC不同。

AlarmViewController *receiver = [[AlarmViewController alloc]init];
[receiver setPropertyTextToReceivedText:self.typedText.text];

Answer 2

修改如下:

NSLog(@"text before alarm is created: %@", self.textFromTextVC);

:

NSLog(@"%@: text before alarm is created: %@", self, self.textFromTextVC);

它可能会告诉你，你确实在看同一个类的两个不同的对象实例。

Answer 3

我想你忘记了:

@synthesize textFromTextVC;