方法完成后，是否可以运行代码？

Question

我想在方法完成后开始代码。 我有一个UICollectionView ，它从服务器加载图像数组，然后将这些图像添加到我创建的单元格中的ImageView中，以更好地在这里解释我的代码：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellID = @"cellID";
    insightCell *myCell = (insightCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellID forIndexPath:indexPath];
    myCell.tag = [[[objectiveGov n_insights] objectAtIndex:indexPath.item]integerValue];
    imgTag = ((UICollectionView *)myCell).tag;
//This is the Method I want to run "ObjectiveGov is the NSObject which has my Method inside "arrayImages" which is separate to the view controller this UICollectionView is in.
    [objectiveGov arrayImages];

//Possible if statement here, that records when the method above is finished.
    myCell.insightImageView.image = [theInsightImage objectAtIndex:indexPath.item];
            return myCell;
        }

因此，一旦方法[objectiveGov arrayImages]; 完成后，我希望它运行myCell.insightImageView.image 。 有办法吗？ 我尝试创建一个在方法末尾发布的NSNotificationCenter，但这没有用，因为UICollectionViewCell方法在分配UICollectionView时启动。 有任何想法吗？ 谢谢！

编辑 ArrayImages方法代码：

+(void)arrayImages
{
    [[NSNotificationCenter defaultCenter] postNotificationName:@"postArrayImages" object:nil];
    [[NSUserDefaults standardUserDefaults] synchronize];

    NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@/api/insights/get/",URL_ROOT]];
    AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
    NSString *imageString = [NSString stringWithFormat:@"%d",[viewInsightViewController imgTag]];
    NSURLRequest *request = [httpClient requestWithMethod:@"GET" path:imageString parameters:nil];
    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {

        NSDictionary *dictionInsight = [JSON valueForKey:@"results"];
        NSArray *insightArray = [dictionInsight valueForKey:@"images"];
        NSString *fileName = [dictionInsight valueForKey:@"filename"];
        if (fileName == (id) [NSNull null])
        {
//URL incase server file doesnt contain image.
            nineArray = [NSString stringWithFormat:@"http://url.co.uk/images/logo.png"];
        }else {
            nineArray = [insightArray valueForKey:@"96"];
        }
        insightURL = [NSURL URLWithString:nineArray];

         if (insightURL != nil) {
        NSURLRequest *requestImage = [NSURLRequest requestWithURL:insightURL];
        AFImageRequestOperation *imageOperation = [AFImageRequestOperation imageRequestOperationWithRequest:requestImage imageProcessingBlock:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image)
                                                   { 
                                                       if (requestImage != nil) {
                                                           insightImages = image;
                                                           [arrayOfImages addObject:insightImages];                                                      
 }

                                                   } failure:nil];
        [imageOperation start];
         }

Answer 1

对于这种情况，使用块将是完美的。 将您的array images方法更改为类似的方法，以便在完成网络连接后调用该块，以传回已加载的图像。

+ (void)arrayImagesWithCompletionBlock:(void(^)(UIImage *image))completionBlock {
....
       if (insightURL != nil) {
            NSURLRequest *requestImage = [NSURLRequest requestWithURL:insightURL];
            AFImageRequestOperation *imageOperation = [AFImageRequestOperation imageRequestOperationWithRequest:requestImage imageProcessingBlock:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                    if (requestImage != nil) {

                       insightImages = image;
                       [arrayOfImages addObject:insightImages];

                       // Call the completion block here once we have the loaded image
                       completionBlock(image);
                    }];

               } failure:nil];

            [imageOperation start];
        }
....
}

并在cellForIndexPath中这样称呼它：

[objectiveGov arrayImagesWithCompletionBlock:^(UIImage *loadedImage) {
    myCell.insightImageView.image = loadedImage;    
}];

最后一件事，就是在实际要执行objectForKey的地方调用valueForKey。 （valueForKey将获得对象的属性值与所需的字典方法的比较，有关详细信息，请使用谷歌“键值编码”）。

Answer 2

也许你可以带一个条件？ 完成后，让[objectiveGov arrayImages]返回BOOL = YES。

NSCondition *condition = [NSCondition new];
__block BOOL continueThread = NO;

        if ([objectiveGov arrayImages] == YES) {
            continueThread = YES;
            [condition signal];
            [condition unlock];
        } 

while (!continueThread) [condition wait];

不知道它是否会工作..大声思考一下...