ios - 处理 UIButtons iOS

Question

我一直在观看 2013 年冬季的 iOS 讲座(由 Paul Hegerty 主讲)，我似乎无法理解为什么第二行代码在 Matchisimo 程序中是必需的。如果我将其注释掉，程序就会崩溃，但如果我保留它，它会正常工作。

[cardButton setTitle:card.contents forState:UIControlStateSelected];

[cardButton setTitle:card.contents forState:UIControlStateSelected|UIControlStateDisabled];

在这一行失败:

@autoreleasepool {
    return UIApplicationMain(argc, argv, nil, NSStringFromClass([CardGameAppDelegate class]));
}

第二行被注释掉会报错:

'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 47 beyond bounds [0 .. 46]'

卡片内容:

@property (strong, nonatomic) NSString *contents;

更新用户界面:

- (void)updateUI
{
    for (UIButton *cardButton in self.cardButtons) {
        Card *card = [self.game cardAtIndex:[self.cardButtons indexOfObject:cardButton]];

        [cardButton setTitle:card.contents forState:UIControlStateSelected];

        [cardButton setTitle:card.contents forState:UIControlStateSelected|UIControlStateDisabled];

        cardButton.selected = card.isFaceUp;
        cardButton.enabled = !card.isUnPlayable;
    }
}

Answer 1

注释此行 [cardButton setTitle:card.contents forState:UIControlStateSelected|UIControlStateDisabled]; 不会因任何原因导致崩溃。

这是行 [self.game cardAtIndex:[self.cardButtons indexOfObject:cardButton]]; 导致与索引越界相关的崩溃。基本上你拥有的 cardButtons 比 self.game 拥有的卡片更多。

您可以用它包装它以防止崩溃，但应该寻找更深层次的潜在问题，了解为什么要创建额外的按钮。

int buttonIndex = [self.cardButtons indexOfObject:cardButton];
if (self.game.count > buttonIndex) {
    Card *card = [self.game cardAtIndex:buttonIndex];

    [cardButton setTitle:card.contents forState:UIControlStateSelected];

    [cardButton setTitle:card.contents forState:UIControlStateSelected|UIControlStateDisabled];

    cardButton.selected = card.isFaceUp;
    cardButton.enabled = !card.isUnPlayable;
}