In this lesson, you will learn how to use preprocessor directives to isolate platform-specific logic, ensuring your multiplayer game executes code only when targeted at the appropriate device.
Controlling Compilation with Preprocessor Directives
When building a multiplayer game that spans across both PC (Desktop) and Mobile, you often encounter architectural differences. For instance, you might want to use high-fidelity physics synchronization on a desktop build but opt for a more aggressive, lightweight networking approach on mobile to preserve battery life and accommodate restricted bandwidth.
Unity uses preprocessor directives to handle this. These are special compiler instructions that tell Unity to "include" or "exclude" specific blocks of code depending on the current Build Target. When you compile your project, the C# compiler effectively ignores the code contained within an "inactive" directive, meaning that code won't even exist in the final build for that specific platform.
Practical Implementation
Imagine you have a PlayerController script that handles input differently based on the platform. You can wrap your platform-specific logic using the #if directive:
void Update()
{
#if UNITY_STANDALONE_WIN
// Desktop-specific: Use high-precision mouse/keyboard input
ProcessDesktopInput();
#elif UNITY_IOS || UNITY_ANDROID
// Mobile-specific: Use touch-based input
ProcessMobileInput();
#else
// Default fallback
ProcessGenericInput();
#endif
}
By using these defines, you prevent mobile builds from trying to reference desktop-only namespaces or input libraries, which would otherwise result in compilation errors. In a networked environment, this is crucial for managing device-specific settings, such as adjusting NetworkVariable synchronization rates or UI layout logic without bloating your codebase with if/else runtime checks that consume CPU cycles unnecessarily.
Always remember that these directives are evaluated at compile time, not runtime. This means you are essentially stripping out the irrelevant code entirely before the game is even installed on the user’s device, keeping your production binary lean and optimized for the specific hardware it’s running on.
Key Takeaway: Platform-specific scripting defines use preprocessor directives to conditionally compile code, ensuring that platform-specific logic is included only when building for the intended target.