ios - AFHTTPRequestOperation 完成后如何执行函数？

Question

我搜索了很多并看到了一些答案，但我仍然不确定如何解决它:我只想在操作完成时执行一些 void 函数。

我的代码:

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    [request setHTTPBody:[soapBody dataUsingEncoding:NSUTF8StringEncoding]];
    [request addValue:@"text/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPMethod:@"POST"];
    [request addValue:kAPP_PASSWORD_VALUE forHTTPHeaderField:kAPP_PASSWORD_HEADER];
    [request addValue:@"http://blablabla" forHTTPHeaderField:@"SOAPAction"];


    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];

    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
        self.responseXML = [operation responseString];        

        NSData *data = [self.responseXML dataUsingEncoding:NSUTF8StringEncoding];
        [self doParse:data];
        self.numOfWallPosts = [self.sharedPrefs integerForKey:@"total_number_of_wall_posts"];

        for (int i = 1; i <= self.numOfWallPosts; i++)
        {
            NSString *sharedKey = [NSString stringWithFormat:@"wall_number_%d", i];
            NSMutableDictionary *aaa = [[NSMutableDictionary alloc] init];
            aaa = [self.sharedPrefs objectForKey:sharedKey];
            [self handleWallPostsWithWallPost:aaa];
        }
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"\n\nError: %@", error);
    }];

    [operation start];

[self handleWallPostsWithWallPost:aaa]; - 在后台下载一些图像，因此，该 block 已完成，但在后台，有一些图像正在下载。我如何知道图像下载何时完成？

- (void)handleWallPostsWithWallPost:(NSMutableDictionary *)wallPost
{
    NSMutableDictionary *temp = [[NSMutableDictionary alloc] init];
    temp = wallPost;

    NSString *owner = [temp objectForKey:@"owner"];
    NSString *title = [temp objectForKey:@"title"];
    NSString *imageUrl = [temp objectForKey:@"image_url"];
    NSInteger wallId = [[temp objectForKey:@"wall_id"] integerValue];
    NSLog(@"Wall ID: %d | Owner: %@ | Title: %@ | Image URL: %@", wallId, owner, title, imageUrl);

//    arrayOfOwnersImage - Save as NSData

    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:imageUrl]];
    AFImageRequestOperation *operation;
    operation = [AFImageRequestOperation imageRequestOperationWithRequest:request imageProcessingBlock:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
        NSLog(@"Image downloaded...");
        NSData *imageData = UIImageJPEGRepresentation(image, 90);
        [self.arrayOfOwnersImage addObject:imageData];
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
        NSLog(@"Image download fail: %@", [error localizedDescription]);
    }];

    [operation start];
}

有什么想法吗？

Answer 1

我认为您应该采用两种不同的方法来实现这一目标。

第一个简单的方法。使用计数器。使用您需要运行的操作数设置计数器。当操作完成时，计数器将递减。当它为零时，操作完成。确保在操作的完成 block 中递减计数器，并确保在同一线程中执行递减。相反，你会遇到竞争条件问题。

第二种更干净的方式。子类 AFHTTPClient 并使用 – enqueueBatchOfHTTPRequestOperationsWithRequests:progressBlock:completionBlock: 方法。来自 AFNetworking 文档。

Creates and enqueues an AFHTTPRequestOperation to the HTTP client’s operation queue for each specified request object into a batch. When each request operation finishes, the specified progress block is executed, until all of the request operations have finished, at which point the completion block also executes.

NSMutableArray *operations = [NSMutableArray array];

for (id element in elements) {  

    NSMutableURLRequest *request = // your request here

    AFHTTPRequestOperation *operation = [[YourAFHTTPClientSubclass sharedClient] HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, id responseObject) {
        // 
        // Handle success here
        //   

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        // 
        // Handle error here
        //

    }];

    //
    // Add all operations to the operations NSArray
    //
    [operations addObject:operation];
}

//
// Pass off operations array to the sharedClient so that they are all executed
//
[[YourAFHTTPClientSubclass sharedClient] enqueueBatchOfHTTPRequestOperations:operations progressBlock:^(NSUInteger numberOfCompletedOperations, NSUInteger totalNumberOfOperations) {
    NSLog(@"Completed %d of %d create operations", numberOfCompletedOperations, totalNumberOfOperations);
} completionBlock:^(NSArray *operations) {
    //
    // All operations are completed
    //

}];

编辑

在第一个操作中创建一个 dict 元素数组，如下所示

NSMutableArray *elements = [NSMutableArray array];
for (int i = 1; i <= self.numOfWallPosts; i++)
{
    NSString *sharedKey = [NSString stringWithFormat:@"wall_number_%d", i];
    NSMutableDictionary *aaa = [[NSMutableDictionary alloc] init];
    aaa = [self.sharedPrefs objectForKey:sharedKey];
    [elements addObject:aaa];
}

[self handleWallPostsWithWallPost:elements];

现在，handleWallPostsWithWallPost: 将包含我提供的代码。

elements 是传递给方法的元素字典数组。 for 循环允许您创建图像操作。