Dynamic Constructor in C++ with Examples

What are Constructors in C++?

In C++ programming, Constructors are used for initializing objects. They are responsible for setting up the initial state of an object when it is created. While traditional constructors are static, which means that they are called automatically when an object is instantiated.

Dynamic constructors offer a more flexible and powerful alternative. In this article, you will learn all about dynamic constructors in C++, exploring their features, benefits, and best practices for implementation.

Dynamic Constructor in C++ with Examples

The constructor can allocate dynamically created memory to the object and thus object is going to use the memory region which is dynamically created by the constructor.

In simple words, We can say that whenever the allocation of memory is done dynamically using a new keyword inside a constructor, it is called a dynamic constructor. When you use the dynamic memory allocator 'new' inside the constructor to create dynamic memory.

Dynamic constructors in C++ enable the allocation of resources and execution of code at runtime. It allows more dynamic object initialization. Unlike static constructors, which are predefined and executed automatically during object creation, it offers greater control over object initialization and resource allocation. By using it, you can dynamically initialize the objects.

Benefits of Dynamic Constructors:

1. Resource Allocation Flexibility: It empowers developers to allocate resources dynamically at runtime. It enables efficient memory management and resource utilization.

2. Conditional Initialization: With it, you can conditionally initialize objects based on runtime parameters or external factors. It provides enhanced flexibility in object initialization.

3. Dynamic Initialization: It facilitates the execution of code at runtime. It allows for dynamic initialization of objects based on dynamic conditions or user input.

4. Reduced Memory Footprint: By dynamically allocating resources only when needed, it helps minimize memory overhead and improve application performance.

5. Exception Handling: It enables robust exception-handling mechanisms. It allows developers to handle initialization errors and exceptions during runtime.

Implementation of Dynamic Constructors:

To implement dynamic constructors in C++, follow the given steps:

1. Define Dynamic Constructors: Declare dynamic constructors within your class definition using the 'dynamic_constructor' keyword followed by the constructor name. For example:

#include<iostream.h>
using namespace std;
class MyClass {
public:
    dynamic_constructor MyClass(); // Dynamic constructor declaration
};

2. Implement Dynamic Constructors: Defining its implementation outside the class definition using the dynamic_constructor keyword. For example:

#include<iostream.h>
using namespace std;
dynamic_constructor MyClass::MyClass() {
    // Dynamic constructor implementation
}

3. Invoke Dynamic Constructors: Invoke dynamic constructors explicitly using the dynamic_constructor keyword followed by the constructor name. For example:

#include<iostream.h>
using namespace std;
MyClass obj;
dynamic_constructor obj.MyClass();

Point To Remember:

1. It does not create the memory of the object but it creates the memory block that is accessed by the object.

2. You can also give arguments you want to declare as shown in Example 2. 

Example 1:

#include<iostream>
using namespace std;

class Mania
{
  const char* ptr;

public:

  // default constructor
  Mania()
  {
    // allocating memory at run time
    ptr = new char[15];
    ptr = "Learning Mania";
  }

  void display()
  {
    cout << ptr;
  }
};

int main()
{
  Mania obj1;
  obj1.display();
}

Output:

Learning Mania

Example 2:

#include<iostream>
using namespace std;

class Mania
{
  int num1;
  int num2;
  int *ptr;
 
public:
  // default constructor (here, it is dynamic constructor also)
  Mania()
  {
    num1 = 0;
    num2 = 0;
    ptr = new int;
  }
 
  //dynamic constructor with parameters
  Mania(int x, int y, int z)
  {
    num1 = x;
    num2 = y;
    
    ptr = new int;
    *ptr = z;
  }
 
 void display()
 {
   cout << num1 << " " << num2 << " " << *ptr;
 }
};

int main()
{
  Mania obj1;
  Mania obj2(3, 5, 11);
 
  obj1.display();
  cout << endl;
  
  obj2.display();
}

Output:

0 0 0
3 5 11

Best Practices for Using Dynamic Constructor in C++:

1. Keep Initialization Lightweight: Avoid heavy computations or resource allocations within it to ensure efficient object initialization and runtime performance.

2. Handle Initialization Errors: Implement robust error-handling mechanisms to handle initialization errors and exceptions during runtime.

3. Minimize Dependency on External Factors: Reduce dependencies on external factors or runtime conditions to maintain code reliability and portability.

4. Test Thoroughly: Conduct comprehensive testing to verify the correctness and robustness of dynamic constructors under various runtime scenarios.

5. Document Usage Guidelines: Document the usage guidelines and best practices for dynamic constructors to facilitate collaboration and ensure code maintainability.