Organize Code with Local Swift Packages

There are several benefits to organizing your code into modules:

• Readability
• Testability
• Reusability
• Maintainability
• And more …

By using an Xcode Workspace and Swift Packages, a monolithic project can be split up and organized, into smaller modules or packages. Utilities, for example, can go in one package, and the Data Layer can go in another package.

Swift Packages can be local or remote. If the module can be used by other projects or teams, then consider using a remote package. In which case, the remote package will require its own git repository. If the module is only usable by the main application, then use a local package. The local package will live within the git repository of the main application. In this article, we’re going to use a local package.

The Steps Link to heading

The following steps describe how to add a local “MyLibrary” package to an “Example” project.

Using Xcode 16

1. Checkout the starter-project on GitHub: https://github.com/harrisonrw/swift-local-package-example

The example project is a simple SwiftUI app.

Using the Project Navigator, make note of the initial project structure.

Foo.swift contains a struct that will be moved to a Swift Package.

struct Foo {
    var bar = 0
}

ContentView.swift defines the UI in a SwiftUI View. There is a state property for Foo. A button displays the current value of foo.bar. When the button is pressed, the value of foo.bar is incremented.

// ...
struct ContentView: View {
    @State var foo = Foo()
    // ...
    Button("Counter = \(foo.bar)") {
        foo.bar += 1
    }
//...

2. Create a Workspace. Name it Example.xcworkspace and save it in the same directory as the .xcodeproj file. See Manage Multiple Projects with an Xcode Workspace to learn how to create an Xcode Workspace.

3. Create a Swift Package by clicking File > New > Package.

4. Choose a Template (Multiplatform > Library). Click Next.

5. Choose a Testing System. Click Next.

6. Set Save As to “MyLibrary” in the same directory as the .xcodeproj and .xcworkspace files.

7. Set Add to, to the name of the workspace: “Example”.

8. Verify your configuration matches the screenshot below and then click Create.

9. In Project Navigator, the file structure should look something like this:

10. Move Foo.swift to MyLibrary:

11. Try to build the Example app. It should fail with Cannot find 'Foo' in scope.

12. Since Foo is in a separate package, we need to add the package dependency to the “Example” project. Under Project > Package Dependencies, click on the + button.

13. Click Add Local.

14. Select the folder that contains the package: “MyLibrary”. Click Add Package.

15. Click Add Package again.

16. MyLibrary should added to the Example project:

17. Add this line to ContentView.swift to import MyLibrary:

import MyLibrary

18. Try to build the Example app again. It should still fail with Cannot find 'Foo' in scope. We need to make Foo accessible to callers outside of the package.

19. In Foo.swift, mark the struct and property as public. Also create a public initializer because the default init has internal protection level.

public struct Foo {
    public var bar = 0
    public init() { }
}

20. Build the Example app again. This time it should succeed.

For reference, you can checkout the final project on GitHub: https://github.com/harrisonrw/swift-local-package-example

Conclusion Link to heading

Now you can apply these same steps to organize and improve the modularity of your own projects. Thank you for reading.