Question

我想在方法完成后启动代码。我有一个 UICollectionView ，它从服务器加载一个图像数组，然后将这些图像添加到我创建的单元格中的ImageView中，以便更好地解释这里是我的代码：

- (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，我希望它运行myCell.insightImageView.image。有办法做到这一点吗？我尝试创建一个在方法结束时发布的NSNotificationCenter但这不起作用，因为UICollectionViewCell方法在分配UICollectionView时启动。有任何想法吗？谢谢！

修改 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

使用块对于这种情况是完美的。将数组图像方法更改为类似的方法，以便在完成afnetworking时调用块传回加载的图像。

+ (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];
        }
....
}

在cellForIndexPath中调用它：

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

最后一件事，你在你想要做objectForKey的地方调用valueForKey。（valueForKey将获得对象的属性值与您想要的字典方法，google“键值编码”获取更多信息）。

Answer 2

也许你可以选择病情？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];

不知道它是否会起作用..只是大声思考......

一旦方法完成，有没有办法运行代码？

2 个答案: