Copy Constructors
There are two specialized constructors: the Copy Constructor and the Move Constructor. Understanding these constructors is crucial for effective resource management, memory allocation, and object manipulation
Copy Constructor
When copying two variables of a primitive type, the process is straightforward and doesn't usually require special consideration. However, copying objects in is a more complex and tricky task. The distinction between shallow copy and deep copy will become clear when you will examine the following code:
main.cpp
Note
It generates error:
free(): double free detected
| Description | Copies data values as they are, including pointers. | Allocates separate memory and copies actual values. |
| Pointers | Copies the address of the pointers directly. | Creates a new memory location and copies the value pointed to. |
| Memory Use | Uses the same memory locations as the original. | Allocates new memory locations for copied data. |
| Resource Handling | Can lead to issues like double free. | Prevents resource conflicts by creating separate copies. |
| Use Case | Suitable for simple structures without dynamic memory allocation. | Essential for objects with dynamic memory management. |
| Performance | Generally faster due to direct copying. | Slower due to memory allocation and value copying. |
| Safety | Risky in managing resources, prone to errors. | Safer, as it ensures independent copies of resources. |
Note
That is precisely why a copy constructor is essential. It enables us to perform a deep copy, ensuring safety in the process.
Syntax of Copy Constructor
Creating a copy constructor shares some similarities with creating a constructor, yet it has its own distinctive features. The general approach to creating a copy constructor as usual is outlined below:
- Name: the copy constructor has the same name as the class. It does not have any unique prefix or symbol to differentiate it from the regular constructor.
- Parameter Type: it takes a single parameter, typically a reference to a constant object of the same class.
- No Return Type: similar to other constructors and the destructor, the copy constructor does not have a return type, not even void.
- Special Usage: it is called automatically by the compiler in specific scenarios, such as when an object is passed by value to a function, returned from a function, or initialized using another object of the same class.
main.cpp
The Rule of Three
There is a guideline for classes that manage dynamically allocated memory or other resources. It states that if it needs to provide a custom implementation for any of the following three methods:
- Destructor (
~Example()). - Copy constructor (
Example(const Example&)). - Copy assignment operator (
Example& operator=(const Example&)).
Then it often needs to provide implementations for all three of them. This is because if a class manages resources that require custom cleanup or copying behavior, the default implementations provided by the compiler may not be suitable.
Which of the following describes a deep copy?
Select a few correct answers
Everything was clear?
Course Content
C++ OOP
C++ OOP
Copy Constructors
There are two specialized constructors: the Copy Constructor and the Move Constructor. Understanding these constructors is crucial for effective resource management, memory allocation, and object manipulation
Copy Constructor
When copying two variables of a primitive type, the process is straightforward and doesn't usually require special consideration. However, copying objects in is a more complex and tricky task. The distinction between shallow copy and deep copy will become clear when you will examine the following code:
main.cpp
Note
It generates error:
free(): double free detected
| Description | Copies data values as they are, including pointers. | Allocates separate memory and copies actual values. |
| Pointers | Copies the address of the pointers directly. | Creates a new memory location and copies the value pointed to. |
| Memory Use | Uses the same memory locations as the original. | Allocates new memory locations for copied data. |
| Resource Handling | Can lead to issues like double free. | Prevents resource conflicts by creating separate copies. |
| Use Case | Suitable for simple structures without dynamic memory allocation. | Essential for objects with dynamic memory management. |
| Performance | Generally faster due to direct copying. | Slower due to memory allocation and value copying. |
| Safety | Risky in managing resources, prone to errors. | Safer, as it ensures independent copies of resources. |
Note
That is precisely why a copy constructor is essential. It enables us to perform a deep copy, ensuring safety in the process.
Syntax of Copy Constructor
Creating a copy constructor shares some similarities with creating a constructor, yet it has its own distinctive features. The general approach to creating a copy constructor as usual is outlined below:
- Name: the copy constructor has the same name as the class. It does not have any unique prefix or symbol to differentiate it from the regular constructor.
- Parameter Type: it takes a single parameter, typically a reference to a constant object of the same class.
- No Return Type: similar to other constructors and the destructor, the copy constructor does not have a return type, not even void.
- Special Usage: it is called automatically by the compiler in specific scenarios, such as when an object is passed by value to a function, returned from a function, or initialized using another object of the same class.
main.cpp
The Rule of Three
There is a guideline for classes that manage dynamically allocated memory or other resources. It states that if it needs to provide a custom implementation for any of the following three methods:
- Destructor (
~Example()). - Copy constructor (
Example(const Example&)). - Copy assignment operator (
Example& operator=(const Example&)).
Then it often needs to provide implementations for all three of them. This is because if a class manages resources that require custom cleanup or copying behavior, the default implementations provided by the compiler may not be suitable.
Which of the following describes a deep copy?
Select a few correct answers
Everything was clear?
