objective-c - 在 AFNetworking 请求中等待完成块完成

Question

我正在使用 AFNetworking 发出 JSON 请求，然后调用 [operation waitUntilFinished] 来等待操作以及成功或失败块。但是，它似乎是正确的——就日志消息而言，我得到“0”、“3”、“1”而不是“0”、“1”、“3”

NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://google.com"]];
AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
httpClient.parameterEncoding = AFFormURLParameterEncoding;
NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys:@"query", @"q", nil];
NSMutableURLRequest *request = [httpClient requestWithMethod:@"GET" path:[url path] parameters:params];
NSLog(@"0");
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *innerRequest, NSHTTPURLResponse *response, id JSON) {
 NSLog(@"1");
 gotResponse = YES;
} failure:^(NSURLRequest *innerRequest, NSHTTPURLResponse *response, NSError *error, id JSON) {
  NSLog(@"2");
  gotResponse = YES;
}];
NSLog(@"Starting request");
[operation start];
[operation waitUntilFinished];
NSLog(@"3");

Answer 1

这通过使用 AFNetworking 来设置请求，但进行同步调用然后手动处理完成块来工作。非常简单。AFNetworking 似乎不支持此https://github.com/AFNetworking/AFNetworking/wiki/AFNetworking-FAQ，尽管解决方法很简单。

#import "SimpleClient.h"

#import "AFHTTPClient.h"
#import "AFJSONRequestOperation.h"
#import "AFJSONUtilities.h"

@implementation SimpleClient

+ (void) makeRequestTo:(NSString *) urlStr
        parameters:(NSDictionary *) params
        successCallback:(void (^)(id jsonResponse)) successCallback 
        errorCallback:(void (^)(NSError * error, NSString *errorMsg)) errorCallback {

   NSURLResponse *response = nil;
   NSError *error = nil;

   NSURL *url = [NSURL URLWithString:urlStr];

   AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];

   httpClient.parameterEncoding = AFFormURLParameterEncoding;

   NSMutableURLRequest *request = [httpClient requestWithMethod:@"POST" path:[url path] parameters:params];
   NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

   if(error) {
      errorCallback(error, nil);
   } else {
      id JSON = AFJSONDecode(data, &error);
      successCallback(JSON);
   }
}

@end

Answer 2

这应该（几乎）起作用。您的来电

NSMutableURLRequest *request = [httpClient requestWithMethod:@"GET" path:[url path] parameters:params];

可能不应该传递[url path]给path:参数。在 AFNetworking 领域，该路径是基本 url 之后的所有内容（例如，基本 url 可以是“http://google.com”和路径“/gmail”或其他）。

话虽如此，使用waitUntilFinished将异步操作变为线程阻塞同步操作可能不是一个好主意，但我相信你有你的理由......;）

Answer 3

我只是遇到了同样的问题并找到了不同的解决方案。我有两个相互依赖的操作，但可以并行加载。但是，在第一个操作的完成块完成之前，不能执行第二个操作的完成块。

正如 Colin 所指出的，阻止 Web 请求可能是一个糟糕的选择。这对我来说很重要，所以我是异步完成的。

这是我的解决方案：

// This is our lock
@interface SomeController () {
    NSLock *_dataLock;
}
@end

@implementation

// This is just an example, you might as well trigger both operations in separate
// places if you get the locking right
// This might be called e.g. in awakeFromNib
- (void)someStartpoint {
    AFJSONRequestOperation *operation1 = [AFJSONRequestOperation JSONRequestOperationWithRequest:[NSURLRequest requestWithURL:url1]
                                                                                         success:^(NSURLRequest *request, NSHTTPURLResponse *response, id data) {
        // We're done, we unlock so the next operation can continue its
        // completion block
        [_dataLock unlock];
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id data) {
        // The request has failed, so we need to unlock for the next try
        [_dataLock unlock];
    }];

    AFJSONRequestOperation *operation2 = [AFJSONRequestOperation JSONRequestOperationWithRequest:[NSURLRequest requestWithURL:url2]
                                                                                         success:^(NSURLRequest *request, NSHTTPURLResponse *response, id data) {
        // The completion block (or at least the blocking part must be run in a
        // separate thread
        [NSThread detachNewThreadSelector:@selector(completionBlockOfOperation2:) toTarget:self withObject:data];
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id data) {
        // This second operation may fail without affecting the lock
    }];

    // We need to lock before both operations are started
    [_dataLock lock];

    // Order does not really matter here
    [operation2 start];
    [operation1 start];
}

- (void)completionBlockOfOperation2:(id)data {
    // We wait for the first operation to finish its completion block
    [_dataLock lock];

    // It's done, so we can continue

    // We need to unlock afterwards, so a next call to one of the operations
    // wouldn't deadlock
    [_dataLock unlock];
}

@end

Answer 4

使用委托方法调用

将方法放入块中，该块将在下载/上传完成时调用自身。