Marvel App Assignment

Hi Nick Fury! As requested the iOS App that lists all the best possible Super Heroes. I hope this helps you save the universe. ???

API, Services and Caching

For this assignement I first focussed on creating a generic client side API to load data and images from the official Marvel API. On top of the API I build two services. The Service object is responsible for loading and parsing JSON data from the Marvel Characters endpoint and the ImageService is responsible for downloading images and storing them in the ImageCache. The ImageCache is not much more than a wrapper around NSCache and is the owner of the ImageService and repsonsible for fetching and returning images either from the cache or fresh from the internet.

UX/UI Design

For the visual style and overall look and feel of the app I tried to draw inspiration from data and images returned by the Marvel API and tried to create a matching comic-like style by choosing a very specific set of colors, using thick fonts and fat borders, adding quircky animations and cover everything in animating textures that wouldn’t look out of place in a 1970’s comic book.

Loading Data and images

To populate the super heroes collection view, the view model utilizes a UICollectionViewDiffableDataSource to update snapshots of the data when new characters are loaded. When the user starts scrolling new data is loaded automagically in a paging fashion and images are prefetched through the UICollectionViewDataSourcePrefetching protocol conformance. Making the loading of data and images (almost)completely transparent to the user.

Searching Characters

For the search we again depend heavily on our UICollectionViewDiffableDataSource to apply our filtered data in a new snapshot and animating the collection and layout to its new state. I created a custom SearchAccessoryView class that I pass as the inputAccessoryView of the view controller to make sure it’s always on screen and animates with the showing and hiding of the keyboard.

Transitioning to Detail

To dive deeper into the details of one the characters of your choosing I created a quick and snappy custom view controller transition using UIKits UIViewControllerAnimatedTransitioning and related protocols. The idea was to give the user the feeling you’re really zooming in and out of a character.

What’s next?

If I would have had more time I would have loved to spend it on the following subjects(in no particar order):

  • add unit tests
  • add documentation
  • add loading state
  • improve overview to detail transition
  • optimize image cache
  • simplify and expand JSON models


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