The repository contains the demo for Lesson 4 of MDB's iOS training program, APIs + Concurrency in iOS. The first demo, NotificationCenterVsDelegation, is intended to teach students about NotificationCenter and Delegation as well as the pros and cons of using one over the other. The second demo, MemeGenerator, teaches students about API calls and the CodingKeys protocol. MemeGenerator makes a GET request to the ImgFlip MemeGenerator API and uses CodingKeys to make shape the fetched JSON data into Meme objects. Two other playgrounds are also part of Lesson 4. The two playgrounds, the GCD playground and SRC playground, teach the students about Grand Center Dispatch and Automatic Reference Counting respectively. Lesson 4 slides are also available here.