Skip to main content

C# Fundamentals - Delegates

Delegates

Delegate means 'a representative', just as it's meaning it's implementation is the same as well. You have a delegate representing a function of yours.
A delegate is a wrapper around a pointer to a function ( you might be familiar with function pointers in C++ ). These delegates are also type safe and also have some features that make it way more useful than just a function pointer which we will be going over.
To use delegates first we need to declare one, It's syntax basically looks like this : 
[<modifiers>] delegate [return type] <Name>( [Parameter list])
Eg:
public delegate int MyDelegate(string str);
Delegates can be defined directly under a namespace or under a class.
Delegates can point to either static or instance methods.
To use a delegate we have to first instantiate a delegate. To Instantiate a delegate we have to pass a method as parameter or directly assign.
MyDelegate myDelegate = new MyDelegate(method); // As parameter
MyDelegate myDelegate = method // Directly assigning the method
Can call function with invoke member function or normally as well but using Invoke is better because it shows that it is a delegate (my opinion) 😇.
myDelegate(); // Option 1
myDelegate.Invoke(); // Option 2
So now we will look at how a delegate is used as a callback ( most common use ).
using System;
namespace BitShiftProductions
{    
    public delegate void CallBack(int i);
    public class ClassA
    {
        public void LongRunningTask(CallBack cb)
        {
             for(int i=0;i<100;i++)
               cb(i);
        }
    }    
    public class Program
    {
        static void UseProgressValue(int x)
        {
            Console.WriteLine("Processed : " + x + "%");
        }
        public static void Main(string[] args)
        {
            ClassA objA = new ClassA();
            CallBack callback = new CallBack(UseProgressValue);
            objA.LongRunningTask(callback);
        }
    }
}
Output:
Processed : 0%
Processed : 1%
Processed : 2%
Processed : 3%
.
.
.
Processed : 100%
Now I will introduce you to two properties Method & Target, They use reflection to provide us some details.
Method property :- Has data about the method being held and will display the function name and parameter list when printed.
Target property :- Has data about the object that the method is from. If the method is a static function then it will return null, otherwise it will display object's class data.
Now we will look at a more real world example:
using System;
namespace BitShiftProductions
{    
    public delegate bool MeetsCriteria(int[] intValues);
    public delegate void TargetTester();
    public class IntegerMaster
    {
        private int[] integers;
        public IntegerMaster(int[] ints){integers = ints;}
        public void DoMyIntegersMeetCriteria(MeetsCriteria funcVal)
        {
             if(funcVal(integers))             
                 Console.WriteLine("Meets Criteria For : " + funcVal.Method);             
            else
                Console.WriteLine("Does Not Meet Criteria" + funcVal.Method);
        }
    }    
    public class Program
    {
        static bool AreMultiplesOfTwo(int[] integers)
        {
            for(int i=0;i<integers.Length;i++)
            {
                if(integers[i]%2 != 0)
                    return false;
            }
            return true;
        }
        static bool GreaterThanTen(int[] integers)
        {
            for(int i=0;i<integers.Length;i++)
            {
                if(integers[i] <= 10)
                    return false;
            }
            return true;
        }
        static void PrintValues(TargetTester tester)
        {
            Console.WriteLine("Method of : " + tester.Target);
            tester.Invoke();
        }
        public static void Main(string[] args)
        {
            IntegerMaster ima = new IntegerMaster(new int[]{6,18,2,14,32,64,44});
            ima.DoMyIntegersMeetCriteria(AreMultiplesOfTwo);
            ima.DoMyIntegersMeetCriteria(GreaterThanTen);
            PrintValues(ima.PrintIntegers);
        }
    }
} 
Output:
Meets Criteria For : Boolean AreMultiplesOfTwo(Int32[])
Does Not Meet CriteriaBoolean GreaterThanTen(Int32[])
Method of : BitShiftProductions.IntegerMaster
Value at 0 = 6
Value at 1 = 18
Value at 2 = 2
Value at 3 = 14
Value at 4 = 32
Value at 5 = 64
Value at 6 = 44
Now let's look at what 'delegate chaining' is.
Delegate chaining is a feature that basically allows us to call a list of functions one after another in the order we added them and is a really useful feature especially when starting to work with events in C#.
For adding a new function to the delegate object 
syntax:
delegateObject += function;
For removing a previously added function from the delegate object 
syntax:
delegateObject -= function;
using System;
namespace BitShiftProductions
{    
    public delegate void Display();
    
    public class Program
    {
        static void PrintA(){Console.WriteLine("Printed A");}
        static void PrintB(){Console.WriteLine("Printed B");}
        static void PrintC(){Console.WriteLine("Printed C");}
        public static void Main(string[] args)
        {
            Display display = PrintA;
            display += PrintB;
            display += PrintC;
            display += PrintA;
            display();
            Console.WriteLine("Removing a Print A Function");
            display -= PrintA;
            display();
        }
    }
}
Printed A
Printed B
Printed C
Printed A
Removing Print A Function
Printed A
Printed B
Printed C
You can see that the last instance of PrintA was removed, not the first ,so removing the functions  acts in the form of a stack.
So whatever is added last is taken out first ( LIFO ).
Here is a section of code which is really important to remember while using delegates.
public delegate int GetValue();
static int Return5(){return 5;}
static int Return10(){return 10;}
public class Program
{
   public static void main()
   {
       GetValue getValue = Return5;
       getValue += Return10;
       int x = getValue();
       // x value will be 10
   }
}
The x value is 10 because that was the function that was added last, and when returning... that last function's return value is used.
Another useful feature is the 'Invocation list'.
There is a member function for delegates called ' GetInvocationList() ', It returns an array of delegates that are chained to that specific delegate object.
Eg:
Delegate[] displays = display.GetInvocationList();
for(int i=0;i<displays.Length;i++)
{
    ((Display)displays[i]).Invoke();
}
The above code basically gets an array of functions from the delegate object as type 'Delegate' and in order to use it as we did before, we have to cast it as type 'Display' to invoke it.
You somehow managed to get through all of that... now treat yourself to a snack.😌
For More C# Tutorials, go HERE.
Support Bitshift Programmer by leaving a like on Bitshift Programmer Facebook Page and be updated as soon as there is a new blog post.
If you have any questions that you might have about shaders or unity development in general don't be shy and leave a message on my facebook page or down in the comments.

Assets Worth Checking Out

POPULAR POSTS

Tri-Planar Terrain Shader

How The Tri-Planar Terrain Shader Looks Like Apart from the manually drawn tile footpath the cliff walls and grass has been generated through a tri-planar shader. How The Tri-Planar Terrain Shader Works The shader that we make will work with the existing terrain system and no need for any custom scripts.
The first two textures provided in the terrain settings will be used to texture the terrain :
*Notes:-
First Texture Index:- Texture that appears on cliff sides.Second Texture Index:- Texture that appears on flat surfaces.Any subsequent textures can be used to draw on top of this as usual.Drawing with either first or second texture slot acts as a eraser removing subsequent textures Terrain Shader Tutorial The shader we will make will be working on top the existing terrain shader that Unity provides us.  So that will require accessing the Unity shader repository for your specific version of Unity.
The version of Unity I used to create the shader is version 2017.4.
Most likely there won&…

Access Reflection Probe Data For Custom Shaders

The Unity shader documentation regarding reflection probes is pretty minimal and not at all comprehensive.
This short tutorial is intended to bring reflection probe functionalities to the forefront your future shader writing endevors which is a fancy way of saying "Look at this cool stuff and go and use it somewhere" 😏
Here we will try just the bare minimum of making a shader that reflects the cubemap data from reflection probe and displays it on the object.

These reflection probes are basically objects that store a complete image of the environment surrounding it into a cubemap which then can be read by shaders to create various effects.
More information on how reflection probes work in Unity can be found here :
Using Reflection Probes In Unity

I am not going over how to set up Reflection Probes here only how to access them inside our custom shaders.
So this is what we will be making:
The reflection probe takes in the cubemap only if it is within it's range otherwise i…

Introduction To Regular Expressions [ Regex ]

What Is A Regular ExpressionRegular expression or regex for short is a sequence of characters that defines a search pattern.
Let me simplify this for you.
Imagine you're writing a huge assignment or a report then you realize you misspelled a word and apparently the word was used a couple of hundred times throughout your document, now any sane person living in the 21st century would :
find and replace->”misspelled word”->”correct word”.

Have you ever wondered how the computer checks for the word?
How the words are magically found and replaced?
It just searches the entire document for “word-to-be-searched” and replace the string with the new one.
Imagine this scenario, you are asked to redact phone numbers from a letter, now you don’t know any of the numbers personally, and since the letter contains plenty of numbers that are not just phone numbers and those should not be redacted what would you do then? This is where Regular Expressions come in to play, a regular expression is bas…

Fortnite Procedural Construction Animation Shader

Fortnite Construction Shader This shader is loosely based on the one that was presented by the Fortnite developers in their GDC talk: Inner Working Of Fortnite's Shader-Based Procedural Animations.

 Here is what we will end up with:
This technique requires you to author the 3D model in a certain way, More or less how those Fortnite developers did.
So we need the authored 3D model and the shader that uses data we get from the model to achieve the desired effect.

There are some nuances here and there so make sure you don't miss out on the details.😗
The first step will be preparing the 3D model and putting in the required data. I used Blender 2.79 but any 3D modeling software would do.
3D Model PreparationModel It
Apply Vertex Colors: For the direction of flight
Each color is a component of a vector (x, y, z). This will be considered as local space.
Values range from -1.0 to +1.0 for each component.
Negative values are achieved by using values of less than 0.5 and positive values wi…

Gift Wrapping Convex Hull Algorithm With Unity Implementation

Convex Hull Algorithm Convex Hull algorithms are one of those algorithms that keep popping up from time to time in seemingly unrelated fields from big data to image processing to collision detection in physics engines, It seems to be all over the place. Why should you care? Cus you can do magic with it and it seems so simple to implement when you first hear about it, but when you start thinking about it, you will realize why it's not such a straightforward thing to do.
Now that I got you interested (hopefully) and now we will see just what a convex hull is.
As you may have noticed a perimeter was made with the same points that was given and these perimeter points enclose the entire set of points.
Now we have to clear up the term 'Convex'.
Convex means no part of the object is caved inwards or that none of the internal angles made by the points exceed 180 degrees.
In this example of a concave shape internal angles go beyond 180 degrees.
What are those red lines for? Well...…