11 Frameworks – Bookshelves of Classes
Frameworks are presented as reusable “bookshelves of classes” that bundle related code—functions, classes, and even other frameworks—so you can share, maintain, and reuse functionality across many apps without copy‑pasting. The chapter explains the containment hierarchy (functions inside classes, classes inside frameworks) and why frameworks are ideal for cleaning up projects, fixing bugs in one place, and distributing code to others via repositories. It also notes that this is a special‑topic milestone aimed at developers who want to package and share code rather than build full UIs.
To make the idea concrete, the chapter walks through creating a Cocoa Touch framework called SwiftoFile that encapsulates file reading and writing once handled inline in Chapter 10. You build a small class hierarchy: a base FileContentManager that stores a filename, a FileReader and FileWriter that inherit from it, and a public SwiftoFile facade that exposes simple read/write methods while hiding internal details via access control. Because frameworks must be compiled for the correct target, the chapter shows building the .framework for either a real device (Generic iOS Device) or a simulator, emphasizing that these outputs are not interchangeable due to different architectures.
The second half shows how to consume the framework in an Xcode app by removing now‑duplicate read/write functions, importing the framework, embedding it in the project, and replacing previous code with a SwiftoFile instance’s read and write calls. It highlights the “Embedded Binaries” step to ensure the app includes the framework at runtime and reminds you to run on a device or simulator that matches how the framework was built. Finally, it connects the concept to UIKit, which you’ve been importing all along—another example of a framework—reinforcing how frameworks streamline code reuse, organization, and collaboration.
The “What-contains-what?” diagram.
The Project Template Pane.
“Cocoa Touch Framework”, the template you should choose.
The Xcode Project screen.
New File Template screen
Giving the file a Name.
“Universe of The Framework”, an Inheritance diagram.
Device Menu, with “Generic iOS Device” selected.
Dragging the Framework file into our Xcode Project.
Putting the Framework file into the Xcode Project
File Navigator in Xcode
The Xcode Project Screen
“Embedded Binaries” Add Page
Check Your App-Knowledge
- Why do you have to build for simulators and iDevices differently when you make a framework?
- What is the advantage of using a framework over functions and classes?
- Why do we use the keyword “public” in some classes when creating a framework?
- Why do you not see files like “Main.storyboard” when you create a framework project in Xcode?
- Describe 2 situations where creating a new framework could be useful.
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