Conditional Compilation in Swift: Making Cross-Platform Apple Apps Work

I am currently building an app the will exist across multiple apple platforms (MacOS, iOS and iPadOS) and during this process I noticed that some features won’t work on other apple platforms.
For example I was building a feature that required camera access for my ios app.

The Problem: Different devices work differently!

• iPhones/iPads: Have cameras, can take photos

• Mac computers: Might not have cameras, work differently

• Apple Watch: Definitely can't take photos!

Unfortunately, the iOS Simulator runs in a sandboxed environment that doesn't have access to macOS hardware due to apple’s strict security policies.
We can use conditional compilation blocks to prevent compiling for specific enivronments such as Simulator.

#if targetEnvironment(simulator)
        // Camera does not work on the simulator
        isCameraAvailable = false
#else
        isCameraAvailable = UIImagePickerController.isSourceTypeAvailable(.camera)
#endif
    }
#endif
}

What it does:

#if targetEnvironment(simulator) - This checks if the app is running in the iOS Simulator (not on a real device)

• If running in Simulator: Sets isCameraAvailable = false because the iOS Simulator cannot access the Mac's camera hardware.

• If running on real device: Uses UIImagePickerController.isSourceTypeAvailable(.camera) to check if the device actually has a working camera.

You can also use conditional compilation to:

Require a minimum operating system version for a feature

This would limit your apps minimum deployment target withing a specific range of operating systems.

/// Swift
if #available(iOS 15.4.1, *) {
    // On iOS, this branch runs in versions 15.4.1 and greater. 
    // On any other OS, this branch runs in any version of that OS.
} else {
   // This branch runs in earlier iOS versions.
}

To learn more about conditional compilation check out Apple Documentation.