iphone - 为什么我在两个 vc 之间的委托(delegate)不起作用？

Question

我有两个 View Controller 。我的第一个是我的菜单，其中包含我的高分和一个按钮，该按钮对我的第二个 View Controller (即我的游戏)执行模式转换。每当我的玩家超过他的高分而输掉游戏时，我希望它在菜单上更新。

现在，当我的玩家输掉游戏时，我创建了一个带有 2 个按钮的 UIAlertView，第一个是主菜单，第二个是重启。这是我尝试通过委托(delegate)更新我的高分的简化代码。

        @protocol highScoreProtocol <NSObject>

        -(void)updateHighScore:(int) score;


        @end

        @interface ViewController : UIViewController <UIAlertViewDelegate> //i have this delegate implemented because i have a uiialertview
        @property (nonatomic) int score;
        @property (nonatomic, weak) id <highScoreProtocol> delegateHighScore;



        @implementation ViewController
        @synthesize score=_score;
        @synthesize delegateHighScore=_delegateHighScore;

            -(void)lostGame{
            [self.delegateHighScore updateHighScore:self.score]; //this is where i try to call the method that should update my high score if necessary but this doesn't actually work
        UIAlertView *losingScreen=[[UIAlertView alloc]initWithTitle:@"Game Over" message:[NSString stringWithFormat:@"Your Score Is %d", self.score] delegate:self cancelButtonTitle:@"Main Menu" otherButtonTitles:@"Restart", nil]; //once the user loses the game i have an alert view show giving the option to either restart the game or go to the main menu where the high score is
            }

        -(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
              if (buttonIndex==0) {
                 //here i'm segueing back to my main menu because he would have pressed the 'main menu' button  [self performSegueWithIdentifier:@"MainMenu" sender:self];

            } else if (buttonIndex==1){
                //here i just reset my attributes and reset my level because he would have pressed the 'restart button'
            }
        }

    @end

            @interface MenuVC : UIViewController <highScoreProtocol>
            @property (weak, nonatomic) IBOutlet UILabel *labelHighScore; //the labelhighscore is the highscore number

            @end


@implementation MenuVC

- (void)viewDidLoad
{
    [super viewDidLoad];
    ViewController *vc=[[ViewController alloc]init];
    vc.delegateHighScore=self;//here is set the delegate as myself which i think i'm supposed to do for some reason

}

-(void)updateHighScore:(int)score{
    if (score>[self.labelHighScore.text integerValue]) { 
        self.labelHighScore.text=[NSString stringWithFormat:@"%d", score];
    }
    NSLog(@"does this method even run");

// this is the method that updates the highscore which I want to run
// but it doesn't, notice I even made an 'nslog' to see if the method
// even runs but I never ever even got a log out in the debugger,
// so this method never runs.
}

如果我只是需要一点帮助，或者如果我做的每件事都完全错误并且以错误的方式完成这项任务，请告诉我。

Answer 1

这不起作用，因为:

ViewController *vc=[[ViewController alloc]init];
vc.delegateHighScore=self;

实例化一个新的 View Controller ，它与您正在与之交互的 View Controller 完全无关。

我假设您正在使用 Storyboard，因此，为您的 View Controller 创建一个标识符(在界面构建器上 -> 选择您的 View Controller -> 身份检查器选项卡 -> 在显示 Storyboard ID 的地方写一个名称)

然后添加这个而不是以前的代码:

ViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:@"yourIdentifier"];
vc.delegateHighScore = self;

编辑:

将此添加到您的按钮操作(但从界面构建器中删除 segue 并从 viewDidLoad 中删除此代码)

ViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:@"yourIdentifier"];
vc.delegateHighScore = self;
[self presentModalViewController:vc animated:YES];