04_读书笔记_RAC中的RACReplaySubject

• RACReplaySubject 是 RACSubject的子类

基本使用

#import "ViewController.h"
#import 

@interface ViewController ()

@end

@implementation ViewController

// 注意:下面的代码如果 RACSubject 直接创建的对象 是 不能执行成功的
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    
    // 1.订阅信号
    RACReplaySubject *subject = [RACReplaySubject subject];
    
    // 3.发送信号
    [subject sendNext:@"RACReplaySubject的信号"];
    
    // 2.订阅信号
    [subject subscribeNext:^(id  _Nullable x) {
       
        NSLog(@"第1个订阅信号中的内容是: %@", x);
    }];
    
    [subject subscribeNext:^(id  _Nullable x) {
        
        NSLog(@"第2个订阅信号中的内容是: %@", x);
    }];
    
    [subject subscribeNext:^(id  _Nullable x) {
        
        NSLog(@"第3个订阅信号中的内容是: %@", x);
    }];
    
}

@end

执行过程

RACReplaySubject.png

• 创建信号

// RACSubject
// 还是调用类的创建
+ (instancetype)subject {
    return [[self alloc] init];
}

// RACReplaySubject
// init 子类重写了

@property (nonatomic, assign, readonly) NSUInteger capacity;

// These properties should only be modified while synchronized on self.
@property (nonatomic, strong, readonly) NSMutableArray *valuesReceived;

- (instancetype)init {
    return [self initWithCapacity:RACReplaySubjectUnlimitedCapacity];
}

- (instancetype)initWithCapacity:(NSUInteger)capacity {

    self = [super init]; // 调用父类 创建一个订阅者数组
    
    _capacity = capacity;
    
    // 创建一个数组 用于保存 发送的信号值
    _valuesReceived = (capacity == RACReplaySubjectUnlimitedCapacity ? [NSMutableArray array] : [NSMutableArray arrayWithCapacity:capacity]);
    
    return self;
}

• 订阅信号

// 1.创建订阅者和父类是一样的, 保存nextBlock

// 2.真正的订阅信号 进行了重写
- (RACDisposable *)subscribe:(id)subscriber {
    RACCompoundDisposable *compoundDisposable = [RACCompoundDisposable compoundDisposable];

    RACDisposable *schedulingDisposable = [RACScheduler.subscriptionScheduler schedule:^{
        @synchronized (self) {
            
            // 如果  self.valuesReceived 有值 就直接发送信号
            // 如果没有,就和父类相同, 将信号的值 进行保存
            for (id value in self.valuesReceived) {
                if (compoundDisposable.disposed) return;
                
                // 发送数组中的每一个值.
                [subscriber sendNext:(value == RACTupleNil.tupleNil ? nil : value)];
            }

            if (compoundDisposable.disposed) return;

            if (self.hasCompleted) {
                [subscriber sendCompleted];
            } else if (self.hasError) {
                [subscriber sendError:self.error];
            } else {
                
                // 保存数据
                RACDisposable *subscriptionDisposable = [super subscribe:subscriber];
                [compoundDisposable addDisposable:subscriptionDisposable];
            }
        }
    }];

    [compoundDisposable addDisposable:schedulingDisposable];

    return compoundDisposable;
}

• 发送信号

- (void)sendNext:(id)value {
    @synchronized (self) {

        // 如果已经添加过, 则value有值,不再需要进行添加
        // 如果没有添加,则添加RACTupleNil单例对象,保存到valuesReceived数组中去.
        [self.valuesReceived addObject:value ?: RACTupleNil.tupleNil];
        
        // 调用父类进行遍历所有的订阅者进行发送数据 执行nextBlock
        [super sendNext:value];
        
        // 清空已发送数据
        if (self.capacity != RACReplaySubjectUnlimitedCapacity && self.valuesReceived.count > self.capacity) {
            [self.valuesReceived removeObjectsInRange:NSMakeRange(0, self.valuesReceived.count - self.capacity)];
        }
    }
}