Constructor Delegation

Constructor delegation (also called constructor chaining or forwarding) lets one constructor call another within the same class to reuse common initialization logic.

Syntax of Constructor Delegation

Constructor delegation is usually used within the syntax of an initialization list. It involves the use of the colon (:) operator, followed by the constructor you want to delegate to, and then any additional arguments or parameters that need to be passed.

user_account


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class UserAccount {
public:
    // Primary constructor
    UserAccount(int userId, int accessLevel)
        : userId(userId), accessLevel(accessLevel)
    {
        // Constructor body
    }

    // Delegating constructor (default accessLevel)
    UserAccount(int userId) : UserAccount(userId, 0) {
        // Constructor body
    }

    int userId;
    int accessLevel;
};

Using initialization lists for constructor delegation is not required, but it's generally recommended for clarity and performance. If needed, you can call an overloaded constructor from another constructor instead.

point


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#include <iostream>

class Point {
public:
    // Delegating constructor to initialize default point at origin
    Point() {
       Point(0, 0);
    }

    // Main constructor
    Point(int x, int y)
        : x(x), y(y) {}

    int x, y;
};

Note

Potential infinite recursion may occur when using constructor delegation. Ensure constructors are structured to avoid recursive invocation loops

Constructors delegation provide multiple benefits in object-oriented programming and are convenient to use, despite any initial complexity they may seem to have.

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Section 2. Chapter 5

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Course Content

C++ OOP

1. Fundamentals of OOP in C++

2. Constructors and Destructors

3. Encapsulation Overview

Introduction to Encapsulation Access Modifiers Keywords Access Modifiers Practice Accessor and Mutator Methods Segmentation and Aggregation The Friend Keyword

4. Inheritance Overview

Introduction to Inheritance Access Modifiers in Inheritance Mulptiple Inheritance Constructor and Destructor in Inheritance Diamond Inheritance The Final Keyword

5. Polymorphism Overview

Introduction to Polymorphism Virtual and Override Keywords Pure Virtual Method Operator Overloading Summary and Overview