How to load images asynchronously ? - UIKit in Objective-C using ReactiveCocoa

Summary: How to load images asynchronously ? - UIKit in Objective-C using ReactiveCocoa

Description

How to load images asynchronously on iOS ? Here is a way to do this with UIKit in Objective-C using ReactiveCocoa

Note: I wrote this code in 2016 for an interview with a company. This is only for educational purpose.

ReactiveCocoa

ReactiveCocoa is an Objective-C framework inspired by Functional Reactive Programming. It provides APIs for composing and transforming streams of values.

DZRImageManager.h

The header is pretty simple. We hide all the internal of this class and there is only 2 public methods.

• sharedInstance: This property return the shared instance of this singleton.
• fetch: this method returns the result of fetching the image at the provided url

DZRImageManager.m

The implementation relies on NSURLSession for the downloading and on NSCache for caching decoded images. Also there is an extra NSURLCache that is used in order to cache the network responses.

The fetch method use flattenMap to combine the result of 2 operations:

• download: does the download in the background
• decode: decode the image in the background