As part of Apple's effort to introduce more and more extension points into the iOS ecosystem, iMessage extensions were added in iOS 10. iMessage extensions allow your users to access and share content from your app with their friends right inside the Messages app. This chapter will show you exactly how to create an iMessage extension.

You will learn about two different extension types: Sticker packs and iMessage apps. Note that these extensions are called apps and not just extensions. This is because iMessage extensions behave a lot like apps even though they're not apps. Also, iMessage apps are distributed through their own iMessage App Store. You will learn more about this later in this chapter.

First, you will gain a broad understanding of iMessage apps and what possibilities they give you as a developer. Once this is established, you will deep dive into several aspects of iMessage apps in more detail. To be more specific, the following are the topics that will be covered in this chapter:

• Creating a sticker pack for iMessage
• Implementing custom, interactive iMessage apps
• Understanding sessions, messages, and conversations

By the end of this chapter, you'll understand how iMessage apps work and how you can create an experience for your users that is fun and engaging. More importantly, you'll be able to launch an amazing sticker pack that features cats, dogs, or any other type of sticker you'd like to slap on messages you send and receive.