Passing a function as an argument

Unity Engine
1

Hi

I understand that you can pass a function as an argument by setting it up like this:

var foo = function() { print("HELLO!"); };

// define your outer function normally
function boo(passedFunction) {
  passedFunction();
}

boo(foo);

and that you can add an argument to the inner function:

var foo = function( anInt : int ) { print("The number is: " + anInt); };

// define your outer function normally
function boo(passedFunction, anInt : int) {
  passedFunction(anInt);
}

boo(foo, 5);

Is this the most sensible way to approach it, or is there a way I could set it up to be:

boo(foo(5));

etc, which looks more similar to the standard function formatting in the brackets, or would you say thats just not needed? Cheers

2

The way you set it up is how to do it.

3

OK thanks

4

Hi,

That’s working in JS, right?
But in C#, I didn’t get it to work.
What identifier I have to choose for “passedFunction”??

With best regards,
Unity Nerd

5 
using UnityEngine;
using System.Collections;

public delegate void ExampleDelegate (string parameter);


public class MyBehaviour : MonoBehaviour
{
	void Start ()
	{
		SomeHandler (MyTarget);
	}
	
	
	void SomeHandler (ExampleDelegate theDelegate)
	{
		theDelegate ("Hello, delegate!");
	}
	
	
	void MyTarget (string parameter)
	{
		Debug.Log (parameter);
	}
}
1 Like
6

Thank you very much AngryAnt!!!
Great example, works perfect for me!

With best regards,
UnityNerd

7

take off pragma strict if type error

var foo = function() :int {return 123};//print was no int, is nothing

 

// define your outer function normally

function boo(passedFunction):int {

  passedFunction();

}
or
var boo :Function = foo;
 

boo();
8

here is the best and simple way to pass function as an argument using C#

void Start ()
    {
        method1(method2);
    }

    void method1(System.Action getMethod)
    {
        getMethod();
    }

    void method2()
    {
        print("called");
    }
1 Like
9

If you prefer to not define your own delegates, there are indeed built-in ones you can use. For completions sake, others include:

using System;

void CallParameterised (Action<string> theReference)
{
    theReference ("The string");
}


bool CallWithReturn (Func<bool> theReference)
{
    return theReference ();
}


bool CallParameterisedWithReturn (Func<string, bool> theReference)
{
    return theReference ("The parameter");
}

Note that you can add a bunch of parameters to both of them - the generic argument list for Func just has to end with the return type.

3 Likes
10

Thanks for the info @AngryAnt .

Followup question: if I have this code:

public static decimal[] GetRandomEquivalentFraction(Func<int, List<int>> numeratorMethod, List<int> denominators, decimal[] operands)

How would I use a delagate instead of a function call as a parameter? The method numeratorMethod takes in an int as a parameter, and passes back a list of ints. I cannot seem to get the syntax correct in order to replace it with System.Action.

numeratorMethod looks like this:

public List<int> Numerators(int denominator)
{
    return FractionUtils.ParseNumerators(numerators, denominator);
}

And the call within GetRandomEquivalentFraction to numeratorMethod looks like this:

List<int> numerators = numeratorMethod(denominator);