Why are delegate called Type safe function pointer?

Type safe means that the compiler doesn't allow the assignment of the value of another type to a given type.

In the .NET world, almost everything is a type a class is a type, a delegate is a type, an int is a type, and the string is a type.

As a delegate is a type, here comes its biggest advantage.

Suppose, you are asked to create a partially defined method meaning a method where some logic is defined but the rest of the logic will be given by the caller of the method.

let's say you have to create a method that will return the top 10 best actors in the world, but the criteria to call an actor as best is unknown. what will you do? How will you create a method where logic is not defined. Here delegates help.

As delegate is a type we can use it as a method parameter.

public class ActorsBLL
{
public delegate bool isActorWorthSayingBest(Actor actor);
public List BestActors(List allActors, isActorWorthSayingBest _criteria)
{
foeach(var act in allActors)
{
if(isActorWorthSayingBest)
{
yield return act;
}
}
}
}
public class Actor
{
public string Name {get;set;}
public int NoOfFilms {get;set;}
public int NoofNationalFilmFares {get;set;}
}

Now the caller who will call the method will define the criteria for the best actor.

public void Main()
{
List allActors= new List()
{
new Actor(){Name="Aamir Khan",NoOfFilms=58,NoofNationalFilmFares=5},
new Actor(){Name="ShahRukh Khan",NoOfFilms=158,NoofNationalFilmFares=4},
new Actor(){Name="Nazzudin Siddiqui",NoOfFilms=45,NoofNationalFilmFares=1},
}
ActorsBLL obj= new ActorsBLL();
var bestActorList= obj.BestActors(allActors,x=>x.NoofNationalFilmFares>=5);
}

as you can see we are now able to use a lambda expression, as lambdas are nothing but a shorthand method. In the above example, x in lambda means Actor type.

Meaning "isActorWorthSayingBest" can point to any method which returns a bool and takes an Actor type.

4 Replies

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Sachin Singh4y ago
Type safe means that the compiler doesn't allow the assignment of the value of another type to a given type.

In the .NET world, almost everything is a type a class is a type, a delegate is a type, an int is a type, and the string is a type.

As a delegate is a type, here comes its biggest advantage.

Suppose, you are asked to create a partially defined method meaning a method where some logic is defined but the rest of the logic will be given by the caller of the method.
let's say you have to create a method that will return the top 10 best actors in the world, but the criteria to call an actor as best is unknown. what will you do? How will you create a method where logic is not defined. Here delegates help.

As delegate is a type we can use it as a method parameter.
public class ActorsBLL
{
public delegate bool  isActorWorthSayingBest(Actor actor);
public List BestActors(List allActors, isActorWorthSayingBest _criteria)
{
  foeach(var act in allActors)
{
  if(isActorWorthSayingBest)
{
yield return act;
}
}
}

}
public class Actor
{
public string Name {get;set;}
public int NoOfFilms {get;set;}
public int NoofNationalFilmFares {get;set;}
}
Now the caller who will call the method will define the criteria for the best actor.
public void Main()
{
List allActors= new List()
{
  new Actor(){Name="Aamir Khan",NoOfFilms=58,NoofNationalFilmFares=5},
new Actor(){Name="ShahRukh Khan",NoOfFilms=158,NoofNationalFilmFares=4},
new Actor(){Name="Nazzudin Siddiqui",NoOfFilms=45,NoofNationalFilmFares=1},

}
  ActorsBLL obj= new ActorsBLL();
var bestActorList= obj.BestActors(allActors,x=>x.NoofNationalFilmFares>=5);
}
as you can see we are now able to use a lambda expression, as lambdas are nothing but a shorthand method. In the above example, x in lambda means Actor type.
Meaning "isActorWorthSayingBest" can point to any method which returns a bool and takes an Actor type.
Jaydeep Patil4y ago
A delegate declares a ref type that references the name of the anonymous method this is the reason delegate is safe type.
Rajanikant Hawaldar4y ago
Because delegate can reference a method that has the same signature as that of the delegate.
Vishal Yelve4y ago
Please refer to Shivprasad Koirala Sir's Video.

https://www.youtube.com/watch?v=ifbYA8hyvjc