UIButton 块相当于 addTarget:action:forControlEvents: 方法？

Question

我环顾四周，但在互联网上找不到这个，也没有在 Apple 文档的任何地方找到，所以我猜它不存在。

但是有没有 iOS4 块等效的 API：

[button addTarget:self action:@selector(tappy:) forControlEvents:UIControlEventTouchUpInside];

我想这可以使用一个类别来实现，但由于极端懒惰，我不想自己写这个:)

这样的东西会很棒：

[button handleControlEvent:UIControlEventTouchUpInside withBlock:^ { NSLog(@"I was tapped!"); }];

Answer 1

我刚刚实现了这个。它就像一个魅力！

而且这并不难。

typedef void (^ActionBlock)();

@interface UIBlockButton : UIButton {
    ActionBlock _actionBlock;
}

-(void) handleControlEvent:(UIControlEvents)event
                 withBlock:(ActionBlock) action;
@end

@implementation UIBlockButton

-(void) handleControlEvent:(UIControlEvents)event
                 withBlock:(ActionBlock) action
{
    _actionBlock = action;
    [self addTarget:self action:@selector(callActionBlock:) forControlEvents:event];
}

-(void) callActionBlock:(id)sender{
    _actionBlock();
}
@end

Answer 2

有一个添加到常用 Foundation/UI 类的块库：BlocksKit。这是documentation。

它没有继承UIButton，而是添加了UIControl category：

[button addEventHandler:^(id sender) {
    //do something
} forControlEvents:UIControlEventTouchUpInside];

还有对集合（地图、过滤器等）、与视图相关的内容等的块/功能添加。

注意：它不能很好地与 Swift 配合使用。

Answer 3

这是一个工作类别实现。在它的当前形式中，这应该只在DEBUG 中使用。当用户交互和时间很重要时，我将这个类别与一个函数（包括在下面）结合使用来测试各种代码。同样，这仅用于开发/调试目的，不应考虑用于生产，因此 #ifdef DEBUG ;)

#ifdef DEBUG

#import <objc/runtime.h>

static char UIButtonBlockKey;

@interface UIButton (UIBlockButton)

- (void)handleControlEvent:(UIControlEvents)event withBlock:(ActionBlock)block;
- (void)callActionBlock:(id)sender;

@end


@implementation UIButton (UIBlockButton)

- (void)handleControlEvent:(UIControlEvents)event withBlock:(ActionBlock)block {
    objc_setAssociatedObject(self, &UIButtonBlockKey, block, OBJC_ASSOCIATION_COPY_NONATOMIC);
    [self addTarget:self action:@selector(callActionBlock:) forControlEvents:event];
}


- (void)callActionBlock:(id)sender {
    ActionBlock block = (ActionBlock)objc_getAssociatedObject(self, &UIButtonBlockKey);
    if (block) {
        block();
    }
}

@end


void DSAddGlobalButton(NSString *title, ActionBlock block) {
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button setTitle:title forState:UIControlStateNormal];
    [button handleControlEvent:UIControlEventTouchUpInside withBlock:block];
    [button sizeToFit];
    [button setFrame:(CGRect){{100.0f, 100.0f}, [button frame].size}];

    UIView *firstView = [[[[UIApplication sharedApplication] keyWindow] subviews] objectAtIndex:0];
    [firstView addSubview:button];
}


#endif

Answer 4

斯威夫特 4

class ClosureSleeve {
    let closure: () -> ()

    init(attachTo: AnyObject, closure: @escaping () -> ()) {
        self.closure = closure
        objc_setAssociatedObject(attachTo, "[\(arc4random())]", self, .OBJC_ASSOCIATION_RETAIN)
    }

    @objc func invoke() {
        closure()
    }
}

extension UIControl {
    func addAction(for controlEvents: UIControlEvents = .primaryActionTriggered, action: @escaping () -> ()) {
        let sleeve = ClosureSleeve(attachTo: self, closure: action)
        addTarget(sleeve, action: #selector(ClosureSleeve.invoke), for: controlEvents)
    }
}

示例用法：

button.addAction {
    print("button pressed")
}

Answer 5

我为此创建了一个库！

它支持UIControl (UIButton)、UIBarButtonItem 和UIGestureRecognizer。使用 CocoaPods 也支持它。

https://github.com/lavoy/ALActionBlocks

// Assuming you have a UIButton named 'button'
[button handleControlEvents:UIControlEventTouchUpInside withBlock:^(id weakControl) {
    NSLog(@"button pressed");
}];

安装

pod 'ALActionBlocks'

Answer 6

这是我很久以前写的，这不是解决这个问题的方法！！！子类化 UIButton 会创建一个不值得的雷区。使用 Shayne Sweeney 的类别（我刚刚通过一系列调整更新了他的答案，以使他的示例产品准备就绪......希望他们能很快获得批准）。

-----ORIG POST-----

如果您只分配 UIControlEventTouchUpInside，Martin 发布的代码应该可以工作......但有几个问题：

• 如果您多次调用 handleControlEvent:，您将使用发布的代码泄漏块。
• 如果您分配了多种类型的事件，它将触发所有事件的最后一个块

在我的代码中，我依赖 Blocks 被视为 object-c 对象，它只适用于 iOS4+（不是 3.2）。当我想为按钮状态（即动画）做一些特别的事情时，它对我很有效。您可以只使用 clickedButton 块来处理正常点击。

#import <UIKit/UIKit.h>

@interface ButtWithBlockActions : UIButton {
  void (^downBlock_)(void);
  void (^upBlock_)(void);
  void (^clickedBlock_)(void);
}

@property(nonatomic,retain) void (^downBlock)(void);
@property(nonatomic,retain) void (^upBlock)(void);
@property(nonatomic,retain) void (^clickedBlock)(void);

@end



#import "ButtWithBlockActions.h"

@implementation ButtWithBlockActions

- (void)dealloc {
  [downBlock_ release];
  [upBlock_ release];
  [clickedBlock_ release];
  [super dealloc];
}


- (void (^)(void))downBlock { return downBlock_; }
- (void) fireDownBlock { downBlock_(); }
- (void) setDownBlock:(void (^)(void))block {
  if(downBlock_) {
    [self removeTarget:self action:@selector(fireDownBlock) forControlEvents:UIControlEventTouchDown];
    [self removeTarget:self action:@selector(fireDownBlock) forControlEvents:UIControlEventTouchDragEnter];
    [downBlock_ release];
  }
  downBlock_ = [block copy];
  if(downBlock_) {
    [self addTarget:self action:@selector(fireDownBlock) forControlEvents:UIControlEventTouchDown];
    [self addTarget:self action:@selector(fireDownBlock) forControlEvents:UIControlEventTouchDragEnter];
  }
}


- (void (^)(void))upBlock { return upBlock_; }
- (void) fireUpBlock { upBlock_(); }
- (void) setUpBlock:(void (^)(void))block {
  if(upBlock_) {
    [self removeTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchUpInside];
    [self removeTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchUpOutside];
    [self removeTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchDragOutside];
    [self removeTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchCancel];
    [upBlock_ release];
  }
  upBlock_ = [block copy];
  if(upBlock_) {
    [self addTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchUpInside];
    [self addTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchUpOutside];
    [self addTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchDragOutside];
    [self addTarget:self action:@selector(fireUpBlock) forControlEvents:UIControlEventTouchCancel];
  }
}


- (void (^)(void))clickedBlock { return clickedBlock_; }
- (void) fireClickedBlock { clickedBlock_(); }
- (void) setClickedBlock:(void (^)(void))block {
  if(clickedBlock_) {
    [self removeTarget:self action:@selector(fireClickedBlock) forControlEvents:UIControlEventTouchUpInside];
    [clickedBlock_ release];
  }
  clickedBlock_ = [block copy];
  if(clickedBlock_) {
    [self addTarget:self action:@selector(fireClickedBlock) forControlEvents:UIControlEventTouchUpInside];
  }
}

@end

Answer 7

有REKit可以带出Blocks的潜在能力。它使您能够使用 Block 向实例添加/覆盖方法。

使用 REKit，您可以动态创建一个响应 buttonAction 的目标，如下所示：

id target;
target = [[NSObject alloc] init];
[target respondsToSelector:@selector(buttonAction) withKey:nil usingBlock:^(id receiver) {
    // Do something…
}];
[button addTarget:target action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];

您不需要创建子类或类别。

除了目标/动作范式之外，您还可以使用 REKit 进行委托模式。

Answer 8

我发起的基于 Swift 扩展/类别的实现。使用 OBJC 关联对象不是反模式。 :P

import UIKit

// MARK: UIControl Block based actions
typealias ActionBlock = (UIControl) -> ()

class UIButtonActionDelegate : NSObject {
    let actionBlock : ActionBlock
    init(actionBlock: ActionBlock) {
        self.actionBlock = actionBlock
    }
    func triggerBlock(control : UIControl) {
        actionBlock(control)
    }
}

private var actionHandlersKey: UInt8 = 0
extension UIControl {
    var actionHandlers: NSMutableArray { // cat is *effectively* a stored property
        get {
            return associatedObject(self, key: &actionHandlersKey, initialiser: { () -> NSMutableArray in
                return NSMutableArray()
            })
        }
        set { associateObject(self, key: &actionHandlersKey, value: newValue) }
    }

    func addBlockForEvents(events: UIControlEvents, block: ActionBlock) {
        let actionDelegate = UIButtonActionDelegate(actionBlock: block)
        actionHandlers.addObject(actionDelegate) // So it gets retained
        addTarget(actionDelegate, action: #selector(UIButtonActionDelegate.triggerBlock(_:)), forControlEvents: events)
    }
}

// MARK: Associated Object wrapper

func associatedObject<ValueType: AnyObject>(
    base: AnyObject,
    key: UnsafePointer<UInt8>,
    initialiser: () -> ValueType)
    -> ValueType {
        if let associated = objc_getAssociatedObject(base, key)
            as? ValueType { return associated }
        let associated = initialiser()
        objc_setAssociatedObject(base, key, associated,
                                 .OBJC_ASSOCIATION_RETAIN)
        return associated
}

func associateObject<ValueType: AnyObject>(
    base: AnyObject,
    key: UnsafePointer<UInt8>,
    value: ValueType) {
    objc_setAssociatedObject(base, key, value,
                             .OBJC_ASSOCIATION_RETAIN)
}

Answer 9

我发现使用一个小助手类既简单又通用：

@interface Handler : NSObject

@end

@implementation Handler {
    void (^block)(id);
}

+ (Handler *)create:(void (^)(id))block {
    Handler *result = [[Handler alloc] init];

    result->block = block;

    return result;
}

- (void)call:(id)sender {
    block(sender);
}

@end

并像这样使用它：

Handler *handler = [Handler create:^(id sender) {
    // ... handle the event, using local state captured by the block ...
}];

// store the handler because the target is not retained in addTarget
[handlers addObject:handler];

[button addTarget:handler action:@selector(call:) forControlEvents:UIControlEventTouchUpInside];

Answer 10

一个更简单的解决方案（一个没有扩展等）：

void (^eventHandlerBlock)(void) = ^{
    printf("\nHandling event for button %lu\n", some_local_variable);
};
objc_setAssociatedObject(button, @selector(invoke), eventHandlerBlock, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
[button addTarget:eventHandlerBlock action:@selector(invoke) forControlEvents:UIControlEventAllEvents];

将选择器替换为块时需要牢记以下几点：

1. 如果声明块变量static，可以省略objc_setAssociatedObject；但是，您不能使用任何非编译常量（例如some_local_variable）。
2. 您可以将void(^)(void) 替换为dispatch_block_t。