asynchronous UIImageView in custom UITableViewCell

Question

I would like to know how people implement an asynchronous UIImageView loading, if you have it inside a custom UITableViewCell, I've seen quite some examples using GCD, subclassing UIImageView.. all of them must involves NSURLRequest and NSURLConnection. So how do people do this in a subclass of UITableViewCell that has an UIImageView in it?

Answer 1

Look at this category: SDWebImage . It's a image downloader for UIImageView . You place you're image view in your cell, and in the - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath method, just use:

[myImageView setImageWithURL:[NSURL URLWithString:@"example.com/myimage.jpg"]];

Answer 2

I think the simple and ideal way to do this is to do the following steps

1. Inside cellForRowAtIndexPath: check if the image is available locally load it, else fire off nsurl request to download it in a separate thread and show a loading indicator image.
2. On completion of request thread, store the image locally reload tableView.

Answer 3

Here is a very good tutorial which explains asynchronous loading in general....

http://www.raywenderlich.com/4295/multithreading-and-grand-central-dispatch-on-ios-for-beginners-tutorial

You can use the same idea to load your image view..