QTEventBus架构分析

飞线图

简介

QTEventBus 事件总线集中管理事件流,跟ReactiveCocoa函数响应式编程框架类似(Functional reactive programming，简称FRP）能很好的,省略胶水代码.

Event(事件)

支持事件类型有NSString NSObject Notificaton QTJsonEvent QTAppEvent(应用生命周期事件) 等同于RAC里的signal

Subscribe(订阅)

订阅先于事件发布

dispatch(发布)

事件源出发布需要传递的事件

使用前先订阅事件

// QTSub(self, DemoEvent) 是个宏
 [QTSub(self, DemoEvent) next:^(DemoEvent *event) {
        NSLog(@"%ld",event.count);
 }];

宏展开后

// self 事件订阅者 _className_  泛型指定了 next 回调参数类型 subscribeSharedBus 是通过NSObject扩展里实现
#define QTSub(_object_,_className_) ((QTEventSubscriberMaker<_className_ *> *)[_object_ subscribeSharedBus:[_className_ class]])

subscribeSharedBus 在NSObject分类里实现

// 此处是对 QTEventSubscriberMaker 做事件存储以及封装释放的处理 
- (QTEventSubscriberMaker *)subscribeSharedBus:(Class)eventClass{
    return [QTEventBus shared].on(eventClass).freeWith(self);
}

// on是 QTEventSubscriberMaker对象的block属性 用来
- (QTEventSubscriberMaker *(^)(Class eventClass))on{
    return ^QTEventSubscriberMaker *(Class eventClass){
        return [[QTEventSubscriberMaker alloc] initWithEventBus:self
                                                     eventClass:eventClass];
    };
}
// QTEventSubscriberMaker 对象 
@interface QTEventSubscriberMaker()

- (instancetype)initWithEventBus:(QTEventBus *)eventBus
                      eventClass:(Class)eventClass;

@property (strong, nonatomic) Class eventClass; // 事件类型

@property (strong, nonatomic) NSObject * lifeTimeTracker; // QTEventSubscriberMaker释放的时候用

@property (strong, nonatomic) dispatch_queue_t queue;// 事件响应的队列

@property (strong, nonatomic) NSMutableArray * eventSubTypes; // 存储二级事件

@property (strong, nonatomic) QTEventBus * eventBus; // 事件处理对象

@property (copy, nonatomic) void(^hander)(__kindof NSObject *);// 订阅者需要处理的任务

@end

// next:^(DemoEvent *event) {  将创建监听者 并保存至QTEventBusCollection中(内部实现是双向链表)

 [QTSub(self, DemoEvent) next:^(DemoEvent *event) {
        NSLog(@"%ld",event.count);
 }];

- (id)next:(QTEventNextBlock)hander{
    return self.next(hander);
}

- (id(^)(void(^)(id event)))next{
    return ^id(void(^hander)(__kindof NSObject * event)){
        self.hander = hander;
        return [self.eventBus _createNewSubscriber:self];
    };
}

- (id)_createNewSubscriber:(QTEventSubscriberMaker *)maker{
    if (!maker.hander) {
        return nil;
    }
    if (maker.eventSubTypes.count == 0) {//一级事件
        _QTEventToken * token = [self _addSubscriberWithMaker:maker eventType:nil];
        return token;
    }
    NSMutableArray * tokens = [[NSMutableArray alloc] init];
    for (NSString * eventType in maker.eventSubTypes) {
        _QTEventToken * token = [self _addSubscriberWithMaker:maker eventType:eventType];
        [tokens addObject:token];
    }
    _QTComposeToken * token = [[_QTComposeToken alloc] initWithTokens:tokens];
    return token;
}

- (_QTEventToken *)_addSubscriberWithMaker:(QTEventSubscriberMaker *)maker eventType:(NSString *)eventType{
    __weak typeof(self) weakSelf = self;
    NSString * eventKey = __generateUnqiueKey(maker.eventClass, eventType);
    NSString * groupId = [self.prefix stringByAppendingString:eventKey];
    NSString * uniqueId = [groupId stringByAppendingString:@([NSDate date].timeIntervalSince1970).stringValue];
    _QTEventToken * token = [[_QTEventToken alloc] initWithKey:uniqueId];
    BOOL isCFNotifiction = (maker.eventClass == [NSNotification class]);
    if (eventType && isCFNotifiction) {
        [self _addNotificationObserverIfNeeded:eventType];
    }
// 销毁时的回调
    token.onDispose = ^(NSString *uniqueId) {
        __strong typeof(self) strongSelf = weakSelf;
        if (!strongSelf) {
            return;
        }
        BOOL empty = [strongSelf.collection removeUniqueId:uniqueId ofKey:groupId];
        if (empty && isCFNotifiction) {
            [strongSelf _removeNotificationObserver:eventType];
        }
    };

使用runtime 关联QTDisposeBag 管理监听对象 触发时机在监听者如VC dealloc后会释放关联对象

    //创建监听者
    _QTEventSubscriber * subscriber = [[_QTEventSubscriber alloc] init];
    subscriber.queue = maker.queue;
    subscriber.handler = maker.hander;
    subscriber.uniqueId = uniqueId;
    if (maker.lifeTimeTracker) {
        // 销毁 
        [maker.lifeTimeTracker.eb_disposeBag addToken:token];
    }
    [self.collection addObject:subscriber forKey:groupId];
    return token;
}

以上是订阅事件做的工作.接下来看事件发布的处理

- (IBAction)dispatchEvent:(id)sender {
    static long _count = 1;
    DemoEvent * event = [[DemoEvent alloc] init];
    event.count = _count;
    _count ++;
    [[QTEventBus shared] dispatch:event];
}

- (void)dispatch:(id)event{
    if (!event) {
        return;
    }
    NSString * eventSubType = [event respondsToSelector:@selector(eventSubType)] ? [event eventSubType] : nil;
    if (eventSubType) {
        //二级事件
        NSString * key = __generateUnqiueKey(event.class, eventSubType);
        [self _publishKey:key event:event];
    }
    //一级事件
    NSString * key = __generateUnqiueKey(event.class, nil);
    [self _publishKey:key event:event];
}

根据 key 到collection 取出订阅者 并执行handle任务

- (void)_publishKey:(NSString *)eventKey event:(NSObject *)event{
    NSString * groupId = [self.prefix stringByAppendingString:eventKey];
    NSArray * subscribers = [self.collection objectsForKey:groupId];
    if (!subscribers || subscribers.count == 0) {
        return;
    }
    for (_QTEventSubscriber * subscriber in subscribers) {
        if (subscriber.queue) { //异步分发
            dispatch_async(subscriber.queue, ^{
                if (subscriber.handler) {
                    subscriber.handler(event);
                }
            });
        }else{ //同步分发
            if (subscriber.handler) {
                subscriber.handler(event);
            }
        }

    }
}

到此结束

总结

1, 订阅者存储使用字典加链表的方式
2,DSL链式编程
3,泛型的应用
4,释放池的关联
https://github.com/LeoMobileDeveloper/QTEventBus