UIAlertController Objective-C的布尔值

Question

A button triggers an alert; the alert is "one-time", appearing once but never appearing again after user hits "OK".

If the Boolean is 0, the alert is triggered; if it is 1, then the alert is not triggered. If the user hits "OK", the value of the BOOL is set to 1.

Which is the best way to set a one-time alert in Objective-C?

Answer 1

I would use NSUserDefaults to store the boolean flag you're talking about. Like so:

static NSString * const AlertHasBeenShownUserDefaultsKey = @"AlertHasBeenShownUserDefaultsKey";

-(void)showAlert {
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    if (![userDefaults boolForKey:AlertHasBeenShownUserDefaultsKey]) {
        //Show an alert

        [userDefaults setBool:YES forKey:AlertHasBeenShownUserDefaultsKey];
    }
}

NSUserDefaults will keep the bool value across launches. The value will be reset if the user reinstalls the app though.