How to load images asynchronously ? adding associated objects.
Summary: How to load images asynchronously ? adding associated objects.
Description
How to load images asynchronously on iOS ? Here is a way to do this with UIKit in Objective-C using ReactiveCocoa and associated objects.
Note: I wrote this code in 2016 for an interview with a company. This is only for educational purpose.
Associated Objects
Associated Objects—or Associative References, as they were originally known—are a feature of the Objective-C 2.0 runtime, introduced in OS X Snow Leopard (available in iOS 4). The term refers to the following three C functions declared in <objc/runtime.h>, which allow objects to associate arbitrary values for keys at runtime:
- objc_setAssociatedObject
- objc_getAssociatedObject
- objc_removeAssociatedObjects
Why is this useful? It allows developers to add custom properties to existing classes in categories, which is an otherwise notable shortcoming for Objective-C.
More info about that on NSHipster .
UIImageView+DZRImageManager.h
The header is pretty simple. We hide all the internal of this category on UIImageView and there is only 1 methods.
dzr_setImageWithURL: This property set the image that will be asynchronously loaded onto theUIImageView.
UIImageView+DZRImageManager.m
This category relies on the previously described DZRImageManager for doing the image loading work.
The objective-C runtime is used in order to retain the ReactiveCocoa disposable with the UIImageView .