C++ Tutorial Index

C++ Tutorial C++ History C++ Installation C++ First Program C++ cin and cout C++ Data type C++ Variable C++ operator C++ Keywords

C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ For loop C++ While loop C++ Do while loop

C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

Miscellaneous

C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Constructor Vs Destructor C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor C++ vs C# Malloc() and new in C++ Palindrome Number Program in C++ Snake Code in C++ Splitting a string in C++ Structure Vs Class in C++ Virtual Function Vs Pure Virtual Function C++ Bidirectional Iterators C++ Forward Iterators C++ Iterators C++ Output Iterators C++ Range-based For Loop Converting string into integer in C++ LCM Program in C++ Type conversion in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ Armstrong Number Program in C++ ATM machine program in C++ using functions Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++ Exception Handling in C++ vs Java Const Keyword in C++ Type Casting in C++ Static keyword in C++ vs Java Inheritance in C++ vs Java How to concatenate two strings in C++ Programs to Print Pyramid Patterns in C++ swap() function in C++ Structure of C++ Program Stringstream in C++ and its applications rand() and srand() in C / C++ C++ Ternary Operator C++ Scope of Variables While Loop Examples in C++ Star pattern in C++ using For Loops For Loop Examples in C++ Do-While Loop Examples in C++ Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert Int to String Continue in C++ While loop Diamond Pattern in C++ using For Loop How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using For Loop How to Reverse a String in C++ using While Loop Infinite loop in C++ Loops in C++ Returning Multiple Values from a Function using Tuple and Pair in C++ wcscpy(), wcslen(), wcscmp() Functions in C++ Auto keyword in C++ C++ 11 vs C++ 14 vs C++ 17 C++ STL (Standard Template Library) Differences Between C Structures and C++ Structures Divide by Zero Exception in C++ Dynamic Constructor in C++ Dynamic Memory Allocation in C++ Find the Size of Array in C/C++ without using sizeof() function Floating Point Operations and Associativity in C, C++ and Java Hello World Program in C++ How to create a table in C++ How to Setup Environment for C++ Programming on Mac Implementation of a Falling Matrix in C++ Message Passing in C++ Pointer to Object in C++ Templates in C++ vs Generics in Java Ways to Copy a Vector in C++ What does Buffer Flush mean in C++ sort() function in C++ Structure Sorting (By Multiple Rules) in C++ Similarities between C++ and Java std::distance in C++

C++ Aggregation

C++ Aggregation Definition: In C++, aggregation is a process in which one class (as an entity reference) defines another class. It provides another way to reuse the class. It represents a HAS-A relationship association, or it has class and relationship.

Note: HAS-A relation simply means dynamic or run-time binding.

To qualify as an aggregation, an object must define the following relationships:

  1. The member must be a part of a class.
  • A member can belong to or more classes at a time.
  • The member does not have any existence managed by the object.
  • The member is unknown about the object's existence.
  • The relationship is uni-directional.

Collectively, aggregation is a part-whole relationship, where the parts (member) are contained within the entire uni-directional relationship. However, unlike composition, members can belong to one object at a time. The entire object doesn't need to be responsible for the existence and lifespan of the members. In simple and sober language, aggregation is not responsible for creating or destroying the members or parts.

For instance, consider a relationship between a person and their home address. However, the same address may belong to more than one person at a time in some significant order. Although, it is not managed by the person; the address existed even before the man and will tend to exist even after it. Additionally, a person knows where he/she lives, but the address does not have any information about what person lives. Therefore, it is an example of an aggregate relationship.

Let us dive into the syntax of aggregation.

Syntax:

 Class PartClass
 {
 //instance variables
 //instance methods
 }
 class Whole
 {
 PartClass* partclass;
 } 

In the above syntax, the whole class represents the class that is a container class. The container class is considered as the class for the other part class, which is again contained in the entire class's object. Here, each object of class as the whole can hold the reference pointer of the part class's object.

Implementing Aggregations

In the previous example, we came across how address and person serve the aggregation relation. Similarly, consider the points which help in understanding how aggregations are implemented:

Compositional Nature: Aggregation resembles compositions because they represent the part-whole relationship. They are implemented identically in the same fashion with a slight difference in the semantics.

Member Constraints: In aggregation, we also add parts as member variables. However, these members are references or pointers that point to the object created outside the scope of the class. Thus, aggregation takes objects which point as constructor parameters. The objects and sub-objects are later added by functions and operations.

Existence: Since the parts may exist outside the scope, class destruction may lead to member variable destruction (but not deletion). The parts will exist consequently.

Let us now look at a programming example to understand aggregation better.

 #include<bits/stdc++.h>
 using namespace std;
 class Address
 {
     public:
         int houseNo;
         string colony,city, state;
         Address(int hno, string colony, string city, string state)
 {
         this->houseNo = hno;
         this->colony=colony;
         this->city = city;
         this->state = state;
   }
 };
 class Person
 {
     private:
         Address* address;
     public:
         string name;
         Person(string name, Address* address)
 {
         this->name = name;
         this->address = address;
     }
 void display()
 {
     cout<< name<< " "<< " "<< address->houseNo<<" "<<address-> colony<<" " <<address->city<< " "<<address->state<<endl;
 }
 };
 int main(void)
 {
 Address add1= Address(007 ,"Ampitheatre Park","China Gate","San        Fransisco, CA");
 Person p1 = Person("Andrew's Address:->",&add1);
 Person p2 = Person("Stacy's Address: ->",&add1);
 p1.display();
 p2.display();
 }
 return 0; 

Output:

C++ Aggregation

Explanation:

In the above code, Here Person has an instance variable name that tells the name of the person and a pointer variable to address the class object. Address class object has variables such as House, street, city, and state. Here we have two persons, Raj and Seema, living at the same address, thus share the same address object add1.

The class Person is defined with an instance variable name which tells the name of the person, and the pointer associated with it tells the address of the class object. We have initially assigned two persons, namely Andrew and Stacy, who share the same address as defined in the class with the address as a1. The output address for both Andrew and Stacy will thus be the same.

Advantages of C++ Aggregates:

  1. The aggregation process shows the bi-directional relationship between objects of different classes.
  • The HAS-A relationship provides dependencies that are easy to understand and co-relate.
  • Aggregation provides code reusability and readability. Once the whole class is created, the reference provides the proper access to part classes.
  • It defines a unidirectional relationship that to correctly associates the whole class to the part class.



ADVERTISEMENT
ADVERTISEMENT