iOS-Interview | Comprehensive list of questions and problems to pass | Frontend Framework library

You should start downloading your image in the background with a callback mechanism that can decide if the image should still be displayed after it's been loaded.

One option would be to subclass UIImageView or UITableViewCell and store a reference to the NSURL of the image. Then, when your callback is called, you could check if the image view or the cell's cached URL is the one of the image you have, and decide to display it or not.

I wouldn't recommend on:

• relying on a view's tag as it requires some sort of association table between a NSURL and an integer, which requires a manager object and is not helping reusability of your code
• relying on the cell's indexPath as updates of the table or cells being reused for other index paths could occur while the network request happened

A more advanced options is described in Associated Objects, by NSHipster:

When extending the behavior of a built-in class, it may be necessary to keep track of additional state. This is the textbook use case for associated objects. For example, AFNetworking uses associated objects on its UIImageView category to store a request operation object, used to asynchronously fetch a remote image at a particular URL.