MVVM实战

- (UIViewController *)createInitialViewController {
    self.viewModelServices = [RWTViewModelServicesImpl new];
    self.viewModel = [[RWTFlickrSearchViewModel alloc] initWithServices:self.viewModelServices];
    return [[RWTFlickrSearchViewController alloc] initWithViewModel:self.viewModel];
}

- (void)bindViewModel
{
    self.title = self.viewModel.title;
    RAC(self.viewModel, searchText) = self.searchTextField.rac_textSignal;
　　 self.searchButton.rac_command = self.viewModel.executeSearch; //绑定ViewModel中创建的RACComand
    RAC([UIApplication sharedApplication], networkActivityIndicatorVisible) = self.viewModel.executeSearch.executing;
    RAC(self.loadingIndicator, hidden) = [self.viewModel.executeSearch.executing not];
    [self.viewModel.executeSearch.executionSignals subscribeNext:^(id x) {
        [self.searchTextField resignFirstResponder];
    }];

}

- (void)initialize
{
    self.title = @"Flickr Search";

    RACSignal *validSearchSignal =
    [[RACObserve(self, searchText)
      map:^id(NSString *text) {
        return @(text.length > 3);
    }]
     distinctUntilChanged];

    [validSearchSignal subscribeNext:^(id x) {
        NSLog(@"search text is valid %@", x);
    }];
}

- (RACSignal *)signalFromAPIMethod:(NSString *)method arguments:(NSDictionary *)args transform:(id (^)(NSDictionary *response))block
{
    // 1. 创建请求信号
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {

        // 2. 创建一个Flick请求对象
        OFFlickrAPIRequest *flickrRequest = [[OFFlickrAPIRequest alloc] initWithAPIContext:self.flickrContext];
        flickrRequest.delegate = self;
        [self.requests addObject:flickrRequest];

        // 3. 从代理方法中创建一个信号
        RACSignal *successSignal = [self rac_signalForSelector:@selector(flickrAPIRequest:didCompleteWithResponse:)
                                                  fromProtocol:@protocol(OFFlickrAPIRequestDelegate)];

        // 4. 处理响应
        [[[successSignal
         map:^id(RACTuple *tuple) {
             return tuple.second;
         }]
         map:block]
         subscribeNext:^(id x) {
             [subscriber sendNext:x];
             [subscriber sendCompleted];
         }];

        // 5. 开始请求
        [flickrRequest callAPIMethodWithGET:method arguments:args];

        // 6. 完成后，移除请求的引用
        return [RACDisposable disposableWithBlock:^{
            [self.requests removeObject:flickrRequest];
        }];
    }];
}