如何将ReactiveCocoa与手势识别器一起使用

Question

我正在使用ReactiveCocoa构建应用程序.顶视图是一个菜单,可以向下拉,然后向上推.我必须使用两种不同的手势识别器 - 一种用于拉下,另一种用于推回.一次只能启用一个 - 这就是我的问题.州.

我正在使用BlocksKit扩展来设置手势识别器.

self.panHeaderDownGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithHandler:^(UIGestureRecognizer *sender, UIGestureRecognizerState state, CGPoint location) {
    UIPanGestureRecognizer *recognizer = (UIPanGestureRecognizer *)sender;

    CGPoint translation = [recognizer translationInView:self.view];

    if (state == UIGestureRecognizerStateChanged)
    {
        [self.downwardHeaderPanSubject sendNext:@(translation.y)];
    }
    else if (state == UIGestureRecognizerStateEnded)
    {
        // Determine the direction the finger is moving and ensure if it was moving down, that it exceeds the minimum threshold for opening the menu.
        BOOL movingDown = ([recognizer velocityInView:self.view].y > 0 && translation.y > kMoveDownThreshold);

        // Animate the change
        [UIView animateWithDuration:0.25f animations:^{
            if (movingDown)
            {
                [self.downwardHeaderPanSubject sendNext:@(kMaximumHeaderTranslationThreshold)];
            }
            else
            {
                [self.downwardHeaderPanSubject sendNext:@(0)];
            }
        } completion:^(BOOL finished) {
            [self.menuFinishedTransitionSubject sendNext:@(movingDown)];
        }];
    }
}];

在我的initWithNibName:bundle:方法中,我正在设置以下RACSubjects.

self.headerMovementSubject = [RACSubject subject];
[self.headerMovementSubject subscribeNext:^(id x) {
    @strongify(self);

    // This is the ratio of the movement. 0 is closed and 1 is open.
    // Values less than zero are treated as zero.
    // Values greater than one are valid and will be extrapolated beyond the fully open menu.
    CGFloat ratio = [x floatValue];

    CGRect headerFrame = CGRectMake(0, 0, CGRectGetWidth(self.view.bounds), kHeaderHeight + ratio * kMaximumHeaderTranslationThreshold);

    if (ratio < 0)
    {            
        headerFrame = CGRectMake(0, 0, CGRectGetWidth(self.view.bounds), kHeaderHeight);
    }

    self.headerViewController.view.frame = headerFrame;
}];

// This subject is responsible for receiving translations from a gesture recognizers and turning
// thos values into ratios. These ratios are fead into other signals.
self.downwardHeaderPanSubject = [RACSubject subject];
[self.downwardHeaderPanSubject subscribeNext:^(NSNumber *translation) {
    @strongify(self);
    CGFloat verticalTranslation = [translation floatValue];

    CGFloat effectiveRatio = 0.0f;

    if (verticalTranslation <= 0)
    {
        effectiveRatio = 0.0f;
    }
    else if (verticalTranslation <= kMaximumHeaderTranslationThreshold)
    {
        effectiveRatio = fabsf(verticalTranslation / kMaximumHeaderTranslationThreshold);
    }
    else
    {
        CGFloat overshoot = verticalTranslation - kMaximumHeaderTranslationThreshold;
        CGFloat y = 2 * sqrtf(overshoot + 1) - 2;
        effectiveRatio = 1.0f + (y / kMaximumHeaderTranslationThreshold);
    }

    [self.headerMovementSubject sendNext:@(effectiveRatio)];
}];

// This subject is responsible for mapping this value to other signals and state (ugh). 
self.menuFinishedTransitionSubject = [RACReplaySubject subject];
[self.menuFinishedTransitionSubject subscribeNext:^(NSNumber *menuIsOpenNumber) {
    @strongify(self);

    BOOL menuIsOpen = menuIsOpenNumber.boolValue;

    self.panHeaderDownGestureRecognizer.enabled = !menuIsOpen;
    self.panHeaderUpGestureRecognizer.enabled = menuIsOpen;
    self.otherViewController.view.userInteractionEnabled = !menuIsOpen;

    if (menuIsOpen)
    {
        [self.headerViewController flashScrollBars];
    }
}];

这里有很多事情要做.这个问题因为我已经在这里列出的主题数量几乎翻了一倍(用于泛起手势识别器的主题),再加上另一组用于与页脚进行类似交互的识别器而加剧了这个问题.这是很多科目.

我的问题分为两部分:

1. 有没有更好的方法来设置我想要的链接类型？我在我的俯卧姿势中重新使用了一些主题,看起来非常相似.我有很多,RACSubjects看起来很笨拙.
2. 在menuFinishedTransitionSubject基本上用于管理手势识别器的状态.我试图绑定他们的enabled财产没有任何运气.有什么建议吗？

Answer 1

让我们关注显式订阅,因为这些通常是重写命令式代码的最佳结果.

首先,根据显示的代码,它看起来headerMovementSubject只是来自downwardHeaderPanSubject(和其他地方)的值.这是一个轻松的写作转换的候选人:

RACSignal *headerFrameSignal = [[self.downwardHeaderPanSubject
    map:^(NSNumber *translation) {
        CGFloat verticalTranslation = [translation floatValue];
        CGFloat effectiveRatio = 0.0f;

        // Calculate effectiveRatio.

        return @(effectiveRatio);
    }]
    map:^(NSNumber *effectiveRatio) {
        // Calculate headerFrame.

        return @(headerFrame);
    }];

然后,self.headerViewController.view.frame我们可以使用绑定而不是作为副作用进行操作:

RAC(self.headerViewController.view.frame) = headerFrameSignal;

我们可以在布尔代表中做类似的事情menuFinishedTransitionSubject:

RAC(self.panHeaderDownGestureRecognizer.enabled) = [self.menuFinishedTransitionSubject not];
RAC(self.panHeaderUpGestureRecognizer.enabled) = self.menuFinishedTransitionSubject;
RAC(self.otherViewController.view.userInteractionEnabled) = [self.menuFinishedTransitionSubject not];

不幸的是,-flashScrollBars仍然需要调用副作用,但我们至少可以解除块的过滤:

[[self.menuFinishedTransitionSubject
    filter:^(NSNumber *menuIsOpen) {
        return menuIsOpen.boolValue;
    }]
    subscribeNext:^(id _) {
        @strongify(self);

        [self.headerViewController flashScrollBars];
    }];

如果你想变得非常花哨,很多手势识别器逻辑可以用流转换来表示,动画可以用ReactiveCocoaLayout实现,但这是自己的重写.