Reload own created UITableViewCell - iphone

Question

I got a custom UITableViewcell which should load an Image when use that code:
- (void)setImageWithURL:(NSURL *)URL
{
dispatch_queue_t taskQ = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(taskQ, ^{
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:URL]];
imageView.image = image;
NSLog(#"test");
});
}
It loads the Image very fast, so I get the response "test" very fast, but it needs to load IN the tableView. Also if I select the row it loads the Image.
How can I fix this issue?
Thanks

Answer 1

As long as setImageWithURL: is called as an effect of cellForRowAtIndexPath, then it should should show up as you expect... however, you need to call imageView.image = image; on the main thread. This goes for ALL UI related tasks. So you'll want:
- (void)setImageWithURL:(NSURL *)URL
{
dispatch_queue_t taskQ = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(taskQ, ^{
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:URL]];
dispatch_async(dispatch_get_main_queue(), ^{
imageView.image = image;
NSLog(#"test");
});
});
}
EDIT:
Using NSOperationQueue.
Create an operation queue as a member of your view controller.
m_operationQueue = [NSOperationQueue new];
m_operationQueue.maxConcurrentOperationCount = 1 // if you want to load images in order;
Make sure you cancel operations when the view unloads and when the table will refresh using
[m_operationQueue cancelAllOperations];
Do your thing in setImageWithURL
- (void)setImageWithURL:(NSURL *)URL
{
[m_operationQueue addOperationWithBlock:^{
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:URL]];
dispatch_async(dispatch_get_main_queue(), ^{
imageView.image = image;
NSLog(#"test");
});
}];
}
EDIT again:
Sorry, forgot that setImage was in your custom table cell. You can either:
1) make it a static object that you initialize in the +(void)initialize; method of your cell
2) make it a static object available via class method on your view controller
2) make a singleton instance that is available to your table cell
The design preference is up to you and depends what other practices you've been using if you want to be consistent.

Answer 2

You should call [tableView reloadData] when you finish downloading the image.
There is a similar question with an accepted answer, but also it has a suggestion to use SDWebImage. Take a look: How to get UITableViewCell images to update to downloaded images without having to scroll UITableView