Explanation of "Composition"

Think about real world examples.

Manager is a Employee. (In programing Manager:Employee===> we call it inheritance)

Dog is a Animal. (In programing Dog:Animal===> another inheritance example)

Car has Engine (Has-a means composition in programing world)

public class Car
{
public int ModelNo {get;set;}
public Engine engine {get;set;}
}
public class Engine
{
public int manufacturerName {get;set;}
}

There is another has-a relation which is called Aggregation.

Class has students

public class Class
{
public List students {get;set;}
}
public class Student
{
public string Name{get;set;}
}

Then what is the difference b/w aggregation and composition.

As the name suggests, composition means child will be composed (die) or can't live if parent dies.

Means car can't be useful without engine.

But A classRoom will always be a class room without any student also student can independently exist without class room so it is aggregation but an engine without vehicle doesn't make sense so is composition

2 Replies

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Sachin Singh5y ago
Accepted answer
Think about real world examples.

Manager is a Employee. (In programing Manager:Employee===> we call it inheritance)
Dog is a Animal. (In programing Dog:Animal===> another inheritance example)

Car has Engine (Has-a means composition in programing world)
public class Car
{
public int ModelNo {get;set;}
public Engine engine {get;set;}
}

public class Engine
{
public int manufacturerName {get;set;}

}
There is another has-a relation which is called Aggregation.
Class has students
public class Class
{
public List students {get;set;}

}

public class Student
{
public string Name{get;set;}
}
Then what is the difference b/w aggregation and composition.
As the name suggests, composition means child will be composed (die) or can't live if parent dies.
Means car can't be useful without engine.

But A classRoom will always be a class room without any student also student can independently exist without class room so it is aggregation but an engine without vehicle doesn't make sense so is composition
+1
Srinivasan Ramamoorthi5y ago
You can check this link
https://stackify.com/oop-concepts-composition/
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