OC + RAC(七) RACSubject和RACSignal的区别

-(void)_test8{
    /// RACSubject继承自RACSignal 但是RACSubject和RACSignal的区别？
    //1能接收1，2
    //但是2只能接收2
    RACSubject *subject = [RACSubject subject];
    
    [subject subscribeNext:^(id x) {
        NSLog(@"订阅者1%@", x);
    }];
    
    [subject sendNext:@"subject1"];
    
    [subject subscribeNext:^(id x) {
        NSLog(@"订阅者2%@", x);
    }];
    
    [subject sendNext:@"subject2"];
}