Passing Data in iOS: Delegates, Notifications, and Closures

Updated on September 25th, 2019

⏱ Reading Time: 2 mins

Today, I’m going to discuss about an important and definitely interesting topic which focuses on a quite often overlooked concept. And, this question is commonly asked by beginners:

How do you implement communication internally in apps and exchange messages properly among classes or other entities in Swift projects?

Undoubtedly, it is a must-have knowledge for every developer, new or not. Knowing what the available tools and techniques are, what works best, where and when, is crucial for a proper development process. After all, being able to send messages and data back and forth among classes is not something that one can optionally learn; instead, it’s one of the first things a developer should know about.

So, in this post we are going to see the following methods that allow to perform in-app communication:

  • Delegation pattern
  • Notifications
  • Closures & action handlers

Usually, not all these three concepts are met together in one post, but one can find a lot about each topic separately. I felt the need to write a tutorial that concentrates them all, as they actually serve the same purpose; to let us exchange messages and data among our programming structures and entities. Through simple words and practical programming examples I will try my best to make it easily understandable how each concept works. Hopefully, by the end of the tutorial some valuable lessons will have been taught.

A programming tutorial without a bit of coding doesn’t sound right, so we will work on a demo application that will let us meet each concept as thoroughly as possible given the limits of a single post. For sure, what you will see next are standard techniques which you just have to adjust and use them in your projects. And by having said that, let’s not lose any more time here and let’s move on to the actual interesting stuff! Happy reading!

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