Code Generation

The following are some details about the code generation technology used in Flow, which may help you understand the principles.

IL Post Process

IL Post Process (ILPP) will inject IL to execute event into user's ImplementableEvent method body.

Below is the code decompiled using dnspy.

[ImplementableEvent, ExecutableFunction]
public void ExecuteTest(string data)
{
    Debug.Log("Implement ExecuteTest");
}

If you want to customize the timing for calling bridge methods, you can add bridge method explicitly as shown below.

[ImplementableEvent]
public void Test()
{
    var stopWatch = new Stopwatch();
    stopWatch.Start();
    this.ProcessEvent();
    stopWatch.Stop(); 
    Debug.Log($"{nameof(Test)} used: {stopWatch.ElapsedMilliseconds}ms");
}

Recommended to use the newest version of Rider to view the IL code after ILPP directly.

View IL

Source Generator

In executable function part, it is mentioned that source generator will register static methods to improve runtime performance.

The following shows what SourceGenerator does.

Source code:

/// <summary>
/// Executable function library for ceres
/// </summary>
[CeresGroup("Ceres")]
public partial class CeresExecutableLibrary: ExecutableFunctionLibrary
{
    [ExecutableFunction, CeresLabel("Set LogLevel")]
    public static void Flow_SetLogLevel(LogType logType)
    {
        CeresAPI.LogLevel = logType;
    }
    
    [ExecutableFunction(ExecuteInDependency = true), CeresLabel("Get LogLevel")]
    public static LogType Flow_GetLogLevel()
    {
        return CeresAPI.LogLevel;
    }
}

Generated code:

[CompilerGenerated]
public partial class CeresExecutableLibrary
{
    protected override unsafe void CollectExecutableFunctions()
    {                
        RegisterExecutableFunction<CeresExecutableLibrary>(nameof(Flow_SetLogLevel), 1, (delegate* <LogType, void>)&Flow_SetLogLevel);                
        RegisterExecutableFunction<CeresExecutableLibrary>(nameof(Flow_GetLogLevel), 0, (delegate* <LogType>)&Flow_GetLogLevel);
    }
}

Next Steps