ios - 这个 block 队列中发生了什么？

Question

我正在寻找一种对动画 block 进行排队的方法，偶然发现了这篇博文: http://xibxor.com/2013/03/27/uiview-animation-without-nested-hell/

不过，我无法使其正常工作...如何安排这些元素的范围尚不清楚。另外，第 18、25 和 32 行的那些分号在做什么？谁能解释一下如何使用它？

编辑:这里是从源代码复制的代码:

NSMutableArray* animationBlocks = [NSMutableArray new];

typedef void(^animationBlock)(BOOL);

// getNextAnimation
// removes the first block in the queue and returns it
animationBlock (^getNextAnimation)() = ^{
    animationBlock block = animationBlocks.count ? (animationBlock)[animationBlocks objectAtIndex:0] : nil;
    if (block){
        [animationBlocks removeObjectAtIndex:0];
        return block;
    }else{
        return ^(BOOL finished){};
    }
};

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    [UIView animateWithDuration:1.0 animations:^{
        //...animation code...
    } completion: getNextAnimation()];
}];

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    [UIView animateWithDuration:1.0 animations:^{
        //...animation code...
    } completion: getNextAnimation()];
}];

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    [UIView animateWithDuration:1.0 animations:^{
        //...animation code...
    } completion: getNextAnimation()];
}];

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    NSLog(@"Multi-step Animation Complete!");
}];

// execute the first block in the queue
getNextAnimation()(YES);

Answer 1

首先感谢分享这篇文章，这是个好主意。这非常适合我:

在 @interface 之外的 .h 中:

typedef void(^animationBlock)(BOOL);

然后在你的 .m 中(这里是 - (void)viewDidLoad):

NSMutableArray* animationBlocks = [NSMutableArray new];

UILabel* labelTest = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 50)];
labelTest.text = @"Label Test";

[self.view addSubview:labelTest];

// getNextAnimation
// removes the first block in the queue and returns it
animationBlock (^getNextAnimation)() = ^{
    animationBlock block = animationBlocks.count ? (animationBlock)[animationBlocks objectAtIndex:0] : nil;
    if (block){
        [animationBlocks removeObjectAtIndex:0];
        return block;
    }else{
        return ^(BOOL finished){};
    }
};

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    [UIView animateWithDuration:2.0 animations:^{
        NSLog(@"1-step Animation Complete!");
        labelTest.alpha = 0;
    } completion: getNextAnimation()];
}];

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    [UIView animateWithDuration:2.0 animations:^{
        labelTest.text = @"New text";
    } completion: getNextAnimation()];
}];

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    [UIView animateWithDuration:2.0 animations:^{
        labelTest.alpha = 1;
    } completion: getNextAnimation()];
}];

//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
    NSLog(@"Multi-step Animation Complete!");
}];

// execute the first block in the queue
getNextAnimation()(YES);

这是一个非常简单的动画，但你需要它来测试它^^

希望对您有所帮助。