RACChannelTo(self, name) = RACChannelTo(self.model, name);RACChannelTo(self, blurb) = RACChannelTo(self.model, blurb);RACChannelTo(self, filmType, @(ASHRecipeFilmTypeColourNegative)) = RACChannelTo(self.model, filmType, @(ASHRecipeFilmTypeColourNegative));复制代码

这是一个双向绑定，self.name和self.model.name任何一个改变，另外一个也会改变。第三个参数是默认值，出现nil就用这个来代替。有了它，model和ViewModel就可以双向同步。

RACChannelTerminal *channelA = RACChannelTo(self, valueA);    RACChannelTerminal *channelB = RACChannelTo(self, valueB);    [[channelA map:^id(NSString *value) {        if ([value isEqualToString:@"西"]) {            return @"东";        }        return value;    }] subscribe:channelB];    [[channelB map:^id(NSString *value) {        if ([value isEqualToString:@"左"]) {            return @"右";        }        return value;    }] subscribe:channelA];    [[RACObserve(self, valueA) filter:^BOOL(id value) {        return value ? YES : NO;    }] subscribeNext:^(NSString* x) {        NSLog(@"你向%@", x);    }];    [[RACObserve(self, valueB) filter:^BOOL(id value) {        return value ? YES : NO;    }] subscribeNext:^(NSString* x) {        NSLog(@"他向%@", x);    }];    self.valueA = @"西";    self.valueB = @"左";复制代码