C++ constructors
C++ is a popular programming language used in a wide range of software applications, including desktop software, games, embedded systems, and web applications.
One of the key features of C++ is the ability to define constructors, which are special member functions used to initialize objects of a class.
In this article, we'll explore the basics of C++ constructors, including their syntax, usage, and common patterns.
What is a constructor?
A constructor is a special member function that is called when an object of a class is created.
The purpose of a constructor is to initialize the data members of the class, so that the object is in a valid state.
A constructor has the same name as the class, and no return type.
It is invoked automatically when an object of the class is created, either explicitly or implicitly.
Syntax of a constructor
The syntax of a constructor is similar to that of a function, with a few key differences.
The name of the constructor is the same as the name of the class, and it has no return type.
The body of the constructor contains the initialization code for the data members of the class.
Here's an example of a simple constructor:
vbnet code
class MyClass
{
public: int x;
MyClass()
{
x = 0;
} };
In this example, we define a class called MyClass that has a single data member x. The constructor of the class initializes x to 0.
Usage of constructors
Constructors are used to initialize the data members of a class, so that the object is in a valid state.
Constructors can also be used to allocate memory, set default values, or perform any other initialization tasks that are required for the object to function correctly.
Constructors can be called in two ways: explicitly and implicitly. When an object of a class is created, the constructor is called implicitly. For example:
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MyClass obj;
// Implicit call to the default constructor
In this example, an object of the MyClass class is created using the default constructor, which initializes x to 0.
Constructors can also be called explicitly, using the same syntax as a regular function call. For example:
scssCopy code
MyClass obj(42);
// Explicit call to the parameterized constructor
In this example, an object of the MyClass class is created using the parameterized constructor, which initializes x to 42.
Types of constructors
There are several types of constructors in C++, including:
Default constructor: This constructor takes no arguments and initializes the data members of the class to their default values.
If no constructor is defined for a class, the compiler automatically generates a default constructor.
Parameterized constructor: This constructor takes one or more arguments and initializes the data members of the class based on those arguments.
Copy constructor: This constructor takes a reference to an object of the same class and initializes the new object with the same values as the existing object.
This is used when an object is copied, either explicitly or implicitly.
Move constructor: This constructor takes a reference to an rvalue of the same class and moves the resources owned by the rvalue into the new object.
This is used to efficiently transfer resources from one object to another.
Constructor initialization lists
In C++, constructors can use initialization lists to initialize the data members of a class.
An initialization list is a comma-separated list of data member names and their corresponding initializers, enclosed in parentheses and placed after the constructor's parameter list.
For example:
java code
class MyClass
{
public:
int x;
int y;
MyClass(int a, int b) : x(a), y(b) {}
};
In this example, the constructor of the
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