C++

Destructor in C++

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Destructor in C++

A destructor in C++ is a special member function of a class that is automatically called when an object of the class is destroyed. Its purpose is to clean up any resources that the object has acquired during its lifetime, such as dynamically allocated memory, open files, or network connections.

The syntax for defining a destructor is similar to that of a constructor, but with a tilde (~) preceding the class name:

class MyClass {
public:
  // Constructor
  MyClass() { /* ... */ }
  
  // Destructor
  ~MyClass() { /* ... */ }
};
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The destructor has no parameters and no return value, and its name is always the tilde followed by the class name. Unlike the constructor, the destructor cannot be overloaded, meaning there can be only one destructor per class.

When is a destructor called?

A destructor is called automatically by the C++ runtime system when an object is destroyed. This can happen in several situations, including:

  • When an object goes out of scope:
void myFunction() {
  MyClass myObject;
  // myObject is destroyed when the function ends
}
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  • When an object is dynamically allocated with the new operator:
MyClass* pMyObject = new MyClass();
// ...
delete pMyObject; // The destructor is called here
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  • When an object is a member of another object that is destroyed:
class MyContainer {
public:
  MyContainer() { /* ... */ }
  ~MyContainer() { /* ... */ }

private:
  MyClass myObject;
};

MyContainer container;
// The destructor of MyContainer is called here, which in turn calls the destructor of MyClass
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What does a destructor do?

The primary purpose of a destructor is to release any resources that the object has acquired during its lifetime. This typically involves freeing dynamically allocated memory or closing open files or network connections.

Here is an example of a destructor that frees a dynamically allocated array:

class MyArray {
public:
  MyArray(int size) {
    m_data = new int[size];
    m_size = size;
  }
  
  ~MyArray() {
    delete[] m_data;
  }
  
private:
  int* m_data;
  int m_size;
};
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In this example, the constructor allocates an array of integers using the new operator, while the destructor frees the memory using the delete[] operator.

Do I always need a destructor?

Not necessarily. If your class does not acquire any resources that need to be released, you may not need a destructor. However, if your class has any dynamically allocated memory, open files, or network connections, it is good practice to define a destructor that cleans up those resources.

It’s also worth noting that if you define a destructor, you may also need to define a copy constructor and copy assignment operator to properly handle copying and assigning objects of your class. This is because the default implementations of these functions provided by the compiler may not work correctly with resources that need to be released in the destructor. This concept is known as the rule of three in C++.

Conclusion

A destructor is a special member function in C++ that is automatically called when an object is destroyed. Its primary purpose is to release any resources that the object has acquired during its lifetime, such as dynamically allocated memory, open files, or network connections. If your class acquires any such resources, it is good practice to define a destructor to clean them up properly.

xalgord
WRITTEN BY

xalgord

Constantly learning & adapting to new technologies. Passionate about solving complex problems with code. #programming #softwareengineering

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