Launch Arguments

This sample project aims to show how to get and use launch arguments (or commandline arguments) in a Unity project.

After building the application launch it from the terminal with custom parameters like:

.\LaunchArgumentsSample.exe --portal-user-name "Anton" --app-session-id 1234 --app-avatar-image-url https://placecats.com/neo/256/256

Structure

The relevant parts of the sample project for that are the files Bootstrap.cs and Arguments.cs.

The class Bootstrap is the main entry point for the application and (in this case) the only part of the code that directly makes use of the Arguments class to access launch arguments.

The rest of the app simulates functionality through console logging and basic screen displays, forgoing full implementation of features like multiplayer and avatar loading.

Flow

Below you can find a flowchart for how the Bootstrap class works.

Arguments class

The arguments class is implemented as a Singleton, although it could easily be refactored to a simple MonoBehaviour, ScriptableObject, as a service to be used through a service locator (eg. Reality Collective Service Framework) or any other kind of architecture.

It reads the applications launch arguments and makes them easily available through the TryGet method. Internally it stores all available launch arguments in a Dictionary<string, string> for performant lookup.

API

// The singleton instance of the Arguments class.
static Instance { get; }

// Use this to get any value from the arguments given a key.  
// There is also a non generic version which gets the value as a string, as this is internally what the arguments are stored as.
bool TryGet<T>(string key, out T value)
bool TryGet(string key, out string value)

Example

// > App.exe --my-string-argument "Hello world"

var arguments = Arguments.Instance;

if (arguments.TryGet("my-string-argument", out string myStringArgument))
{
    // do something with the value
    Debug.Log($"Launch argument 'my-string-argument' found: {myStringArgument}");
}
else 
{
    // handle the missing argument
    Debug.LogWarning("Could not find launch argument 'my-string-argument', quitting.");
    Application.Quit();
}

Potential improvements

• Dedicated public properties for common parameters, e.g. in a class derived from Arguments.
• "Toggles" without a value, i.e. boolean value:

  ./App.exe --enable-passthrough --my-string-argument "Hello World"
            ^^^^^^^^^^^^^^^^^^^^

• Also capture other launch parameters, e.g. Unity engine parameters with single dashes (e.g. -screen-fullscreen 0) for easy access inside the application.