Creating and Distributing iOS Frameworks

Michael Katz
ios frameworks tutorial

C’mon on in and learn how to create and distribute iOS frameworks!

Update note: This tutorial has been updated to Xcode 8, Cocoapods 1.0, iOS 10 and Swift 3 on Sept 28, 2016.

Have you ever wanted to share a chunk of code between two or more of your apps, or wanted to share a part of your program with other developers?

Maybe you wanted to modularize your code similarly to how the iOS SDK separates its API by functionality, or perhaps you want to distribute your code in the same way as popular 3rd parties do.

In this iOS frameworks tutorial you’ll learn how to do all of the above!

In iOS 8 and Xcode 6, Apple provided a new template, Cocoa Touch Framework. As you’ll see, it makes creating custom frameworks much easier than before.

Frameworks have three major purposes:

  • Code encapsulation
  • Code modularity
  • Code reuse

You can share your framework with your other apps, team members, or the iOS community. When combined with Swift’s access control, frameworks help define strong, testable interfaces between code modules.

In Swift parlance, a module is a compiled group of code that is distributed together. A framework is one type of module, and an app is another example.

In this iOS frameworks tutorial, you’ll extract a piece of an existing app and set it free, and by doing so, you’ll learn the ins and outs of frameworks by:

  • Creating a new framework for the rings widget
  • Migrating the existing code and tests
  • Importing the whole thing back into the app.
  • Packing it up as an uber-portable CocoaPods
  • Bonus: Setting up a repository for your framework

By the time you’re done, the app will behave exactly as it did before, but it will use the portable framework you developed! :]

Getting Started

Download the Phonercise Starter Project.

Phonercise is a simple application that replicates the Apple Watch Activity app, except it measures your phone’s physical activity. The three rings on the main view represent movement, standing and exercise.

To get the most out of the project, you’ll need to build and run on an actual iOS device, and turn on the volume. Go ahead now, build and run!

ios frameworks tutorial

Move the phone around to get credit for movement, and “exercise” the phone by shaking it vigorously — that’ll get its heartrate up. To get credit for standing up, just hold the phone upright.

The logic for the app is pretty simple:

  • ActionViewController.swift contains the view lifecycle and motion logic.
  • All the view logic is in the files in the Three Ring View folder, where you’ll find ThreeRingView.swift, which handles the view, and Fanfare.swift, which handles the audio. The other files handle the custom drawing of the shading, gradient and shapes.

The ring controls are pretty sweet. They’ve got an addictive quality and they’re easy to understand. Wouldn’t it be nice to use them in a number of applications beyond this fun, but completely silly app? Frameworks to the rescue!

Creating a Framework

Frameworks are self-contained, reusable chunks of code and resources that you can import into any number of apps and even share across iOS, tvOS, watchOS, and macOS apps.

If you’ve programmed in other languages, you may have heard of node modules, packages, gems, jars, etc. Frameworks are the Xcode version of these. Some examples of common frameworks in the iOS SDK are: Foundation, UIKit, AVFoundation, CloudKit, etc.

Framework Set Up

In Xcode 6, Apple introduced the Cocoa Touch Framework template along with access control, so creating frameworks has never been easier. The first thing to do is to create the project for the framework.

  1. Create a new project. In Xcode, go to File/New/Project.
  2. Choose iOS/Framework & Library/Cocoa Touch Framework to create a new framework.
  3. ios frameworks tutorial

  4. Click Next.
  5. Set the Product Name to ThreeRingControl. Use your own Organization Name and Organization Identifier. Check Include Unit Tests. That’s right! You’re going to have automated tests ensure your framework is bug free.

    ios frameworks tutorial

  6. Click Next.
  7. In the file chooser, choose to create the project at the same level as the Phonercise project.

    ios frameworks tutorial

  8. Click Create.

Now you have a project (albeit a boring one) that creates a framework!

Add Code and Resources

Your current state is a framework without code, and that is about as appealing as straight chocolate without sugar. In this section, you’ll put the pod in CocoaPods by adding the existing files to the framework.

From the Phonercise source directory, drag the following eight files into the ThreeRingControl project in Xcode:

  • CircularGradient.swift
  • coin07.mp3
  • Fanfare.swift
  • RingLayer.swift
  • RingTip.swift
  • ThreeRingView.swift
  • Utilities.swift
  • winning.mp3

ios frameworks tutorial

Make sure to check Copy items if needed, so that the files actually copy into the new project instead of just adding a reference. Frameworks need their own code, not references, to be independent.

Double-check that each of the files has Target Membership in ThreeRingControl to make sure they appear in the final framework. You can see this in the File Inspector for each file.

ios frameworks tutorial

Build the framework project to make sure that you get Build Succeeded with no build warnings or errors.

Add the Framework to the Project

Close the ThreeRingControl project, and go back to the Phonercise project. Delete the six files under the Three Ring View group as well as the two MP3 files in Helper Files. Select Move to Trash in the confirmation dialog.

ios frameworks tutorial

Build the project, and you’ll see several predictable errors where Xcode complains about not knowing what the heck a ThreeRingView is. Well, you’ll actually see messages along the lines of “Use of undeclared type 'ThreeRingView'“, among others.

Adding the Three Ring Control framework project to the workspace is the solution to these problems.

Add the Framework to the Project

Right-click on the root Phonercise node in the project navigator. Click Add Files to “Phonercise”. In the file chooser, navigate to and select ThreeRingControl.xcodeproj. This will add ThreeRingControl.xcodeproj as a sub-project.

Note: It isn’t strictly necessary to add the framework project to the app project; you could just add the ThreeRingControl.framework output.

However, combining the projects makes it easier to develop both the framework and app simultaneously. Any changes you make to the framework project are automatically propagated up to the app. It also makes it easier for Xcode to resolve the paths and know when to rebuild the project.

Even though the two projects are now together in the workspace, Phonercise still doesn’t get ThreeRingControl. It’s like they’re sitting in the same room, but Phonercise can’t see the new framework.

Try linking the framework to the app’s target to fix this problem. First, expand the ThreeRingControl project to see the Products folder, and then look for for ThreeRingControl.framework beneath it. This file is the output of the framework project that packages up the binary code, headers, resources and metadata.

Select the top level Phonercise node to open the project editor. Click the Phonercise target, and then go to the General tab.

Scroll down to the Embedded Binaries section. Drag ThreeRingControl.framework from the Products folder of ThreeRingControl.xcodeproj onto this section.

You just added an entry for the framework in both Embedded Binaries and Linked Frameworks and Binaries.

ios frameworks tutorial

Now the app knows about the framework and where to find it, so that should be enough, right?

Build the Phonercise project. More of the same errors.
ios frameworks tutorial

Access Control

Your problem is that although the framework is part of the project, the project’s code doesn’t know about it — out of sight, out of mind.

Go to ActionViewController.swift, and add the following line to the list of imports at the top of the file.

import ThreeRingControl

It’s critical, but this inclusion won’t fix the build errors. This is because Swift uses access control to let you determine whether constructs are visible to other files or modules.

By default, Swift makes everything internal or visible only within its own module.

To restore functionality to the app, you have to update the access control on two Phonercise classes.

Although it’s a bit tedious, the process of updating access control improves modularity by hiding code not meant to appear outside the framework. You do this by leaving certain functions with no access modifier, or by explicitly declaring them internal.

Swift has three levels of access control. Use the following rules of thumb when creating your own frameworks:

  • Public: for code called by the app or other frameworks, e.g., a custom view.
  • Internal: for code used between functions and classes within the framework, e.g., custom layers in that view.
  • Fileprivate: for code used within a single file, e.g., a helper function that computes layout heights.
  • Private: for code used within an enclosing declaration, such as a single class block. Private code will not be visible to other blocks, such as extensions of that class, even in the same file, e.g., private variables, setters, or helper sub-functions.

Ultimately, making frameworks is so much easier than in the past, thanks to the new Cocoa Touch Framework template. Apple provided both of these in Xcode 6 and iOS 8.

Update the Code

When ThreeRingView.swift was part of the Phonercise app, internal access wasn’t a problem. Now that it’s in a separate module, it must be made public for the app to use it. The same is true of the code in Fanfare.swift.

Open ThreeRingView.swift inside of ThreeRingControlProject.

Make the class public by adding the public keyword to the class definition, like so:

public class ThreeRingView : UIView {

ThreeRingView will now be visible to any app file that imports the ThreeRingControl framework.

Add the public keyword to:

  • Both init functions
  • The variables RingCompletedNotification, AllRingsCompletedNotification, layoutSubviews()
  • Everything marked @IBInspectable — there will be nine of these

Note: You might wonder why you have to declare inits as public. Apple explains this and other finer points of access control in their Access Control Documentation.

The next step is to do essentially the same thing as you did for ThreeRingView.swift, and add the public keyword to the appropriate parts of Fanfare.swift. For your convenience, this is already done.

Note that the following variables are public: ringSound, allRingSound, and sharedInstance. The function playSoundsWhenReady() is public as well.

Now build and run. The good news is that the errors are gone, and the bad news is that you’ve got a big, white square. Not a ring in sight. Oh no! What’s going on?

ios frameworks tutorial

Update the Storyboard

When using storyboards, references to custom classes need to have both the class name and module set in the Identity Inspector. At the time of this storyboard’s creation, ThreeRingView was in the app’s module, but now it’s in the framework.

Update the storyboard, as explained below, by telling it where to find the custom view; this will get rid of the white square.

  1. Open Main.Storyboard in the Phonercise project.
  2. Select the Ring Control in the view hierarchy.
  3. In the Identity Inspector, under Custom Class, change the Module to ThreeRingControl.

Once you set the module, Interface Builder should update and show the control in the editor area.

ios frameworks tutorial

Build and run. Now you’ll get some rings.

ios frameworks tutorial

Update the Tests

There’s one final place to update before you can actually use the framework. It’s the oft-forgotten test suite. :]

This app includes unit tests. However, the tests have a dependency on ThreeRingControl, so you need to fix that.

Note: Before Swift 2.0, unit testing was difficult, but Swift 2.0 came along with @testable, making testing far easier. It means you no longer have to make all your project’s items public just to be able to test them.

Simply import the module you want to test using the @testable keyword, and your test target will have access to all internal routines in the imported module.

The first test is ThreeRingTest.swift, which tests functionality within ThreeRingView.swift and should be part of the ThreeRingControl framework.

From the PhonerciseTests group in the app project, drag ThreeRingTest.swift to the ThreeRingControlTests group in the framework project.

Select Copy items if needed, and make sure you select the ThreeRingControlTests target and not the framework target.

ios frameworks tutorial

Then delete the ThreeRingTest.swift from the app project. Move it to the trash.

Open the copied test file, and change the import line from:

@testable import Phonercise


import ThreeRingControl

Click the run test button in the editor’s gutter, and you’ll see a green checkmark showing that the test succeeded.

ios frameworks tutorial

This test doesn’t need @testable in its import since it is only calling public methods and variables.

The remaining app test doesn’t work this way though. Go back the to the Phonercise target and open PhonerciseTests.swift.

Add the following import to the existing imports at the top:

import ThreeRingControl

Now run the PhonerciseTests tests. The particular test should execute and pass.

Congratulations. You now have a working stand-alone framework and an app that uses it!

ios frameworks tutorial

Creating a CocoaPod

CocoaPods is a popular dependency manager for iOS projects. It’s a tool for managing and versioning dependencies. Similar to a framework, a CocoaPod, or ‘pod’ for short, contains code, resources, etc., as well as metadata, dependencies, and set up for libraries. In fact, CocoaPods are built as frameworks that are included in the main app.

Anyone can contribute libraries and frameworks to the public repository, which is open to other iOS app developers. Almost all of the popular third-party frameworks, such as Alamofire, React native and SDWebImage, distribute their code as a pod.

Here’s why you should care: by making a framework into a pod, you give yourself a mechanism for distributing the code, resolving the dependencies, including and building the framework source, and easily sharing it with your organization or the wider development community.

Clean out the Project

Perform the following steps to remove the current link to ThreeRingControl.

  1. Select ThreeRingControl.xcodeproj in the project navigator and delete it.
  2. Choose Remove Reference in the confirmation dialog, since you’ll need to keep the files on disk to create the pod.

Install CocoaPods

If you’ve never used CocoaPods before, you’ll need to follow a brief installation process before going any further. Go to the CocoaPods Installation Guide and come back here when you’re finished. Don’t worry, we’ll wait!

Create the Pod

Open Terminal in the ThreeRingControl directory.

Run the following command:

pod spec create ThreeRingControl

This creates the file ThreeRingControl.podspec in the current directory. It’s a template that describes the pod and how to build it. Open it in a text editor.

The template contains plenty of comment descriptions and suggestions for the commonly used settings.

  1. Replace the Spec Metadata section with:         = "ThreeRingControl"
    s.version      = "1.0.0"
    s.summary      = "A three-ring control like the Activity status bars"
    s.description  = "The three-ring is a completely customizable widget that can be used in any iOS app. It also plays a little victory fanfare."
    s.homepage     = ""

    Normally, the description would be a little more descriptive, and the homepage would point to a project page for the framework.

  2. Replace the Spec License section with the below code, as this iOS frameworks tutorial code uses an MIT License:
    s.license      = "MIT"
  3. You can keep the Author Metadata section as is, or set it u with how you’d lke to be credited and contacted.
  4. Replace the Platform Specifics section with the below code, because this is an iOS-only framework.:
    s.platform     = :ios, "10.0"
  5. Replace the Source Location with the below code. When you’re ready to share the pod, this will be a link to the GitHub repository and the commit tag for this version.
    s.source       = { :path => '.' }
  6. Replace the Source Code section with:
    s.source_files = "ThreeRingControl", "ThreeRingControl/**/*.{h,m,swift}"
  7. And the Resources section with:
    s.resources    = "ThreeRingControl/*.mp3"

    This will include the audio resources into the pod’s framework bundle.

  8. Remove the Project Linking and Project Settings sections.
  9. Add the following line. This line helps the application project understand that this pod’s code was written for Swift 3.
    s.pod_target_xcconfig = { 'SWIFT_VERSION' => '3' }
  10. Remove all the remaining comments — the lines that start with #.

You now have a workable development Podspec.

Note: If you run pod spec lint to verify the Podspec in Terminal, it’ll show an error because the source was not set to a valid URL. If you push the project to GitHub and fix that link, it will pass. However, having the linter pass is not necessary for local pod development. The Publish the Pod section below covers this.

Use the Pod

At this point, you’ve got a pod ready to rock and roll. Test it out by implementing it in the Phonercise app.

Back in Terminal, navigate up to the Phonercise directory, and then run the following command:

pod init

This steathily creates a new file named Podfile that lists all pods that the app uses, along with their versions and optional configuration information.

Open Podfile in a text editor.

Next, add the following line under the comment, # Pods for Phonercise:

pod 'ThreeRingControl', :path => '../ThreeRingControl'

Save the file.

Run this in Terminal:

pod install

With this command, you’re searching the CocoaPods repository and downloading any new or updated pods that match the Podfile criteria. It also resolves any dependencies, updates the Xcode project files so it knows how to build and link the pods, and performs any other required configuration.

Finally, it creates a Phonercise.xcworkspace file. Use this file from now on — instead of the xcodeproj — because it has the reference to the Pods project and the app project.

Check it Out

Close the Phonercise and ThreeRingControl projects if they are open, and then open Phonercise.xcworkspace.

Build and run. Like magic, the app should work exactly the same before. This ease of use is brought to you by these two facts:

  1. You already did the work to separate the ThreeRingControl files and use them as a framework, e.g. adding import statements.
  2. CocoaPods does the heavy lifting of building and packaging those files; it also takes care of all the business around embedding and linking.

Pod Organization

Take a look at the Pods project, and you’ll notice two targets:

ios frameworks tutorial

  • Pods-phonercise: a pod project builds all the individual pods as their own framework, and then combines them into one single framework: Pods-Phonercise.
  • ThreeRingControl: this replicates the same framework logic used for building it on its own. It even adds the music files as framework resources.

Inside the project organizer, you’ll see several groups. ThreeRingControl is under Development Pods. This is a development pod because you defined the pod with :path link in the app’s Podfile. These files are symlinked, so you can edit and develop this code side-by-side with the main app code.

ios frameworks tutorial

Pods that come from a repository, such as those from a third party, are copied into the Pods directory and listed in a Pods group. Any modifications you make are not pushed to the repository and are overwritten whenever you update the pods.

Congratulations! You’ve now created and deployed a CocoaPod — and you’re probably thinking about what to pack into a pod first.

You’re welcome to stop here, congratulate yourself and move on to Where to Go From Here, but if you do, you’ll miss out on learning an advanced maneuver.

Publish the Pod

This section walks you through the natural next step of publishing the pod to GitHub and using it like a third party framework.

Create a Repository

If you don’t already have a GitHub account, create one.

Now create a new repository to host the pod. ThreeRingControl is the obvious best fit for the name, but you can name it whatever you want. Be sure to select Swift as the .gitignore language and MIT as the license.

ios frameworks tutorial

Click Create Repository. From the dashboard page that follows, copy the HTTPS link.

Clone the Repository

Go back to Terminal and create a new directory. The following commands will create a repo directory from the project’s folder.

mkdir repo
cd repo

From there, clone the GitHub repository. Replace the URL below with the HTTPS link from the GitHub page.

git clone URL

This will set up a Git folder and go on to copy the pre-created README and LICENSE files.

ios frameworks tutorial

Add the Code to the Repository

Next, copy the files from the previous ThreeRingControl directory to the repo/ThreeRingControl directory.

Open the copied version of ThreeRingControl.podspec, and update the s.source line to:

s.source       = { :git => "URL", :tag => "1.0.0" }

Set the URL to be the link to your repository.

Make the Commitment

Now it gets real. In this step, you’ll commit and push the code to GitHub. Your little pod is about to enter the big kid’s pool.

Run the following commands in Terminal to commit those files to the repository and push them back to the server.

cd ThreeRingControl/
git add .
git commit -m "initial commit"
git push

Visit the GitHub page and refresh it to see all the files.

ios frameworks tutorial

Tag It

You need to tag the repository so it matches the Podspec. Run this command to set the tags:

git tag 1.0.0
git push --tags

Check your handiwork by running:

pod spec lint

The response you’re looking for is ThreeRingControl.podspec passed validation.

Update the Podfile

Change the Podfile in the Phonercise directory. Replace the existing ThreeRingControl line with:

pod 'ThreeRingControl', :git => 'URL', :tag => '1.0.0'

Replace URL with your GitHub link.

From Terminal, run this in the Phonercise directory:

pod update

Now the code will pull the framework from the GitHub repository, and it is no longer be a development pod!

ios frameworks tutorial

Where to Go From Here?

In this iOS frameworks tutorial, you’ve made a framework from scratch that contains code and resources, you’ve reimported that framework back into your app, and even turned it into a CocoaPod. Nice work!

You can download the final project here. It doesn’t include the “advanced maneuver” steps, as the steps to set up a GitHub repository depends on your personal account information.

Hats off to Sam Davies for developing the ThreeRingControl. You might remember him from such videos as Introducing Custom Controls, where you can learn more about custom controls and custom frameworks.

The team here has put together a lot of tutorials about CocoaPods, and now that you’ve gone through a crash course, you’re ready to learn more. Here are a couple that you might like:

Spend some time at and be sure to check out how to submit to the public pod repository and the dozens of configuration flags.

What did you learn from this? Any lingering questions? Want to share something that happened along the way? Let’s talk about it in the forums. See you there!

Michael Katz

Michael Katz envisions a world where mobile apps always work, respect users’ privacy, and integrate well with their users’ life. When not coding, he can be found with his family playing board games, brewing, gardening, and watching the Yankees.

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