ios - 在所有请求完成后执行代码(Facebook SDK)

Question

是否可以通过委托(delegate)以外的方式从异步完成 block 返回？最好通过调用 block 来传递值吗？

- (NSMutableArray *)facebookGalleryImages
{
    // Create array which will hold dicts for each image containing both thumbnail and original image URLs
    NSMutableArray *allFBImages = [[NSMutableArray alloc] init];
    // Begin Facebook API Calls
    [FBRequestConnection startWithGraphPath:@"me/albums" completionHandler:^(FBRequestConnection* connection, id result, NSError* error) {
        if (!error) {
            // Get data of all albums
            NSArray *feed =[result objectForKey:@"data"];
            for (NSDictionary *dict in feed) {
                // Get album ID of each album
                NSString *albumID = [dict objectForKey:@"id"];
                // New API call to get the image data for a specific album ID
                [FBRequestConnection startWithGraphPath:[NSString stringWithFormat:@"%@/photos", albumID] completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
                    if (!error){
                        // Get data of all images in album
                        NSArray *imageFeed = [result objectForKey:@"data"];
                        // For each image data object, extract source image URL and thumbnail URL, then add these to a dictionary
                        for (NSDictionary *dict in imageFeed){
                            NSString *sourceURL = [dict objectForKey:@"source"];
                            NSString *thumbnailURL = [dict objectForKey:@"picture"];
                            NSDictionary *imageDict = @{ @"source" : sourceURL, @"thumbnail" : thumbnailURL};
                            //Add the dictionary holding an images URLs to an array which will be passed to our gallery
                            [allFBImages addObject:imageDict];
                        }
                    }
                }];
            }
        }
    }];
}

Answer 1

您的返回代码不起作用，因为这些方法是异步的。您能做的最好的事情就是扩展您的方法以在完成时返回，因此您的方法将如下所示:

- (void) facebookGalleryImages:(void (^)(NSMutableArray *imagesArray, NSError *error))completion
{
     NSMutableArray *allFBImages = [[NSMutableArray alloc] init];
     // Begin Facebook API Calls
    [FBRequestConnection startWithGraphPath:@"me/albums" completionHandler:^(FBRequestConnection* connection, id result, NSError* error) {
         if (!error) {
            // Get data of all albums
            NSArray *feed =[result objectForKey:@"data"];
            for (NSDictionary *dict in feed) {
                // Get album ID of each album
                NSString *albumID = [dict objectForKey:@"id"];
                // New API call to get the image data for a specific album ID
                [FBRequestConnection startWithGraphPath:[NSString stringWithFormat:@"%@/photos", albumID] completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
                    if (!error){
                        // Get data of all images in album
                        NSArray *imageFeed = [result objectForKey:@"data"];
                        // For each image data object, extract source image URL and thumbnail URL, then add these to a dictionary
                        for (NSDictionary *dict in imageFeed){
                            NSString *sourceURL = [dict objectForKey:@"source"];
                            NSString *thumbnailURL = [dict objectForKey:@"picture"];
                            NSDictionary *imageDict = @{ @"source" : sourceURL, @"thumbnail" : thumbnailURL};
                            //Add the dictionary holding an images URLs to an array which will be passed to our gallery
                            [allFBImages addObject:imageDict];
                        }
                    }
                }];
            }
            completion(allFBImages, nil);
        }else {
           completion(nil, error);
        }
    }];
}

最后，您将使用您的方法:

[self facebookGalleryImages:^(NSMutableArray *imagesArray, NSError *error) {
     if ([imagesArray count] > 0 ){
         // do something with the array
     }else {
         // do something with error
     }     
};