How do you pass functions as delegates?

[vlOd2]

How do you pass functions as delegates to C# methods/classes that expect a delegate?
For example, there is the winforms method for controlls called Invoke that expects a Delegate
In C#, you'd normally pass your function as an instance of Action by doing Action(My Function)

But how can you do this in Lua? I tried just Invoke(My Function) but that gives Invalid arguments to method: Control.Invoke and I also tried creating an Action by doing Invoke(Action(My Function)) but that gives System.Action does not contain constructor(.ctor) argument match

Also My Function is just a placeholder

[viniciusjarina]

If is an event you can use Add to subscribe to it
like here https://github.com/NLua/NLua/blob/main/extras/examples/form_alt.lua#L27

[vlOd2]

@viniciusjarina That is not the solution, I do know that events can be subscribed to with Add and unsubscribed from by passing the EventHandler returned from add to Remove, I am asking how to create delegate Action and pass that to the Invoke method on controls?

[vlOd2]

In the meantime, I wrote myself a quick workaround, but I wonder if there is any intended way to do what I asked

[vlOd2]

My workaround for those interested:

// You should probably put this in a different table rather than global, like how I did in the code where I use this, but this works too
Script["ControlInvoke"] = new Action<Control, Action>((Control control, Action action) => control.Invoke(action));

[viniciusjarina]

iirc Lua functions can be used to places you expecting a delegate

…

On Tue, Jun 6, 2023 at 11:28 AM vlOd ***@***.***> wrote: My workaround for those interested: Script["ControlInvoke"] = new Action<Control, Action>((Control control, Action action) => control.Invoke(action)); — Reply to this email directly, view it on GitHub <#491 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAHCJFBXIVQPUJ7SKNOWOX3XJ5ZFHANCNFSM6AAAAAAY4WJRBM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[vlOd2]

I tried it, it just throws the exception I said in the issue

[viniciusjarina]

I am not sure what you trying to do. Write a small test case

…

On Fri, Jun 9, 2023 at 3:09 PM vlOd ***@***.***> wrote: I tried it, it just throws the exception I said in the issue — Reply to this email directly, view it on GitHub <#491 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAHCJFCNL722B37XZ3BPITTXKNREVANCNFSM6AAAAAAY4WJRBM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[vlOd2]

I am trying to pass a method to a Delegate parameter, for example System.Windows.Forms.Control.Invoke() takes a delegate, and I tried passing the method directly (Invoke(MyFunc)) but it threw Invalid arguments to method: Control.Invoke and I also tried wrapping it in an Action (Invoke(Action(MyFunc))) as you'd normally do in C#, but that threw System.Action does not contain constructor(.ctor) argument match

[vlOd2]

Here is a test case, the method MyMethodThatTakesADelegate has the arguments as one of the overloads of System.Windows.Forms.Control.Invoke

class Program
{
    static void Main(string[] args)
    {
        MyMethodThatTakesADelegate(new Action(() => 
        {
            Console.WriteLine("Hello from C#!");
        }));

        Lua lua = new Lua();
        lua.LoadCLRPackage();
        lua["MyMethodThatTakesADelegate"] = (Action<Action>)MyMethodThatTakesADelegate;

        try
        {
            /*
             * MyMethodThatTakesADelegate(function() 
             *      print("Hello, world")
             * end)
            */
            lua.DoString("MyMethodThatTakesADelegate(function() print(\"Hello, world\")end)");
        }
        catch (Exception ex) { Console.Error.WriteLine($"First test case failed: {ex}"); }

        try 
        {
            /*
             * import("System")
             * MyMethodThatTakesADelegate(Action(function() 
             *      print("Hello, world")
             * end))
            */
            lua.DoString("import(\"System\") MyMethodThatTakesADelegate(Action(function() print(\"Hello, world\") end))");
        }
        catch (Exception ex) { Console.Error.WriteLine($"Second test case failed: {ex}"); }
        Console.ReadLine();
    }

    public static void MyMethodThatTakesADelegate(Delegate myDelegate) 
    {
        myDelegate.DynamicInvoke();
    }
}

[vlOd2]

Output of test case using the latest version of NLua on .NET 4.7.2 (also on .NET 4.6 where I first discovered this bug/lack of support)

Hello from C#!
First test case failed: NLua.Exceptions.LuaScriptException: [string "chunk"]:1: Cannot invoke delegate (invalid arguments for  MyMethodThatTakesADelegate)
Second test case failed: NLua.Exceptions.LuaScriptException: [string "chunk"]:1: System.Action does not contain constructor(.ctor) argument match