财产不保值

Question

I have a property in my view controller (the app only has one view controller)

@property (weak, nonatomic) NSString * correctAnswer;

In viewDidLoad, I set that property like this and the log statement confirms that it's being set

self.correctAnswer = info.correctAnswer;
NSLog(@"correctAnswer %@", self.correctAnswer);

However, when I click a button in the view and try to inspect that same property in the action (in the same view controller) triggered by the button, it's turning out to be (null) Therefore the string comparison is always wrong. Can you explain what I'm doing wrong?

- (IBAction)checkResponse:(UIButton *)sender {

    UIButton *resultButton = (UIButton *)sender;
    NSLog(@" The button's title is %@.", resultButton.currentTitle);
    NSLog(@"correct answer %@", self.correctAnswer);  //null

    if ([resultButton.currentTitle isEqualToString:self.correctAnswer]){
        NSLog(@"you guessed right");
    }else {
        NSLog(@"You guessed wrong");

    }


}

Answer 1

Change the property from weak to strong (or better yet in this case, copy ).

Weak properties are set to nil as soon as the referenced object is deallocated.