ios - 如何在完成 block 中返回值

Question

我有管理与 AF​​Networking 的连接的类。

所以我想像这样调用我的函数 NSDictionary *dict = [ServerManager requestWithURL:@"https://someurl.com"];

这是另一个类中的函数:

- (NSDictionary *) requestWithURL:(NSString *)requestURL {
    AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] init];
    [manager GET:requestURL parameters:nil progress:nil
         success:^(NSURLSessionDataTask *operation, id responseObject){

             return responseObject;

    }
         failure:^(NSURLSessionDataTask *operation, NSError *error) {

    }];
}

我知道这样做是不正确的。那么我应该怎么做才能将 responseObject 返回给 NSDictionary *dict 呢？我想了解使用 block 进行异步开发的基本概念。

Answer 1

由于网络请求在启动后很长时间内完成，处理结果的唯一方法是将 block 传递给您的请求方法...

// when request completes, invoke the passed block with the result or an error
- (void)requestWithURL:(NSString *)requestURL completion:(void (^)(NSDictionary *, NSError *))completion {
    AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] init];
    [manager GET:requestURL parameters:nil progress:nil success:^(NSURLSessionDataTask *operation, id responseObject){
        if (completion) completion((NSDictionary*)responseObject, nil);
    }, failure:^(NSURLSessionDataTask *operation, NSError *error) {
        if (completion) completion(nil, error);
    }];
}

在 ServerManager.h 中将其公开

- (void)requestWithURL:(NSString *)requestURL completion:(void (^)(NSDictionary *, NSError *))completion;

在其他地方，调用它:

[ServerManager requestWithURL:@"http://someurl.com" completion:^(NSDictionary *dictionary, NSError *error) {
    // check error and use dictionary
}];