Question

I am using Facebook graph to load a user’s image to an iOS app.
The image is then placed inside a UIView in order to present it.

I would like to present that same picture if internet connection is not available, and if internet is available to fetch the image from Facebook.

How do I save the image:

• to NSUserDefaults?
• to Core Data?
• to App folder?

and how do I retrieve it later?

Answer 1

You’re talking about image caching – keep in mind that you can’t just infinitely store images as they are downloaded (there is a chance that your application will take up way too much disk space eventually). You need to define some criteria for purging all of this data – either data that is unused or maybe outdated – that’s up to you. There are a lot of ways to tackle the caching issue, just Google it and I’m sure you’ll find some useful stuff.

As for storing images – what you want to do is get the UIImage’s data (by using functions like UIImageJpegRepresentation or UIImagePNGRepresentation). These functions will return an NSData instance that can either be stored in NSUserDefaults (not the place for image caching) or on a file in your Cache directory (much better and won’t give Apple a good reason to reject your app for bad storage practices).

Also, don’t accidentally try to call these functions on an FBProfilePictureView instance – that’s just a class Facebook created for displaying profile pictures (it is in fact a UIView that has a UIImageView subview of a profile image. Within this UIImageView you can get the UIImage itself). How can I convert FBProfilePictureView to an UIImage?

Good luck