Why we should go for Overriding ?

Naresh Babu Gopavaram

15y2.3k.NET

why overriding in the following situation?

suppose i have like this

class a

{

public virtual int add(int x ,int y)

{

retunt x+y;

}

class a:b

{

public Override int add(int x ,int y)

{

/// some logic here

}

in the above situation i can get the child and parent add() method by creating object on them then why i go for Overriding ?

is there is any performance issues are there ?like memory allocation...etc?

Plz help me ...........

4 Replies

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Vulpes15y ago
Although creating a separate object of the base class wastes memory and you lose the benefit of polymorphism, virtual methods do have a performance cost. This is because the version of the method which gets called is based on the runtime type of the object on which it's called (not its compile time type) and the CLR therefore needs to determine what this is. For example:

A a = new A();
int c = a.Add(1,2); // calls A's version of Add
a = new B();
c = a.Add(1,2); // calls B's version of Add because the runtime type of 'a' is B
B b = new B();
b.Add(1,2); // calls B's version of Add

On the few occasions when the cost of 'late binding' is unacceptable, you can hide a virtual method instead of overriding it using the 'new' keyword:

class A
{
   public virtual int Add(int x ,int y)
   {
   return x + y;
   }
}

class B : A
{
   new public int Add(int x ,int y) // now hides A.Add()
   {
   // some logic here
   }
}

We then have:

A a = new A();
int c = a.Add(1,2); // calls A's version of Add
a = new B();
c = a.Add(1,2); // still calls A's version of Add because the compile time type of 'a' is A
B b = new B();
b.Add(1,2); // calls B's version of Add
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Krishna Garad15y ago
overloading and overriding is the one look of inheritance. One future of oop's is done with this concept i.e. reusability of code again as Mahesh told we don't have to write code again and again. In this again if we have to extend the functionality of base class method in child class we can do it.
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Naresh Babu Gopavaram15y ago
Ok Thank u........
0
Mahesh Chand15y ago
Yes! You're correct. In overriding and overloading, we don't have to use these approaches. But in that case, we have to create separate objects and that takes more allocation in physical memory. By overriding, it is just reference of the class.
0