Default Constructor in C++ with example - Cyborg Coding

A default constructor in C++ is a constructor that has no parameters. It is automatically called when an object of a class is created without any arguments. The default constructor typically initializes the object's properties to their default values. In other words, if a class does not define any constructors, the compiler will automatically provide a default constructor. This default constructor will not have any parameters, and it will not do any initialization. However, if a class defines at least one constructor, the compiler will not provide a default constructor.

For example:

class MyClass {

private:

    int x;

    int y;

public:

    MyClass() {

        x = 0;

        y = 0;

    }

    int getX() { return x; }

    int getY() { return y; }

};

In this example, "MyClass" has a default constructor with no parameters. This constructor initializes the properties "x" and "y" to 0.

MyClass myObject;

This creates an object of the "MyClass" class, and the default constructor is called, initializing the properties "x" and "y" to 0.

The default constructor is a useful feature that allows you to create an object without having to explicitly specify any values for its properties. It is particularly useful when the properties of the class have default values that are appropriate for most situations.

However, default constructors can also create problems when the properties of a class do not have appropriate default values. In such cases, it is important to define a constructor that takes parameters and initializes the properties of the class to appropriate values. This can be done by providing a parameterized constructor or by overloading the default constructor.

For example:

class MyClass {

private:

    int x;

    int y;

public:

    MyClass() {

        x = 0;

        y = 0;

    }

    MyClass(int xVal, int yVal) {

        x = xVal;

        y = yVal;

    }

    int getX() { return x; }

    int getY() { return y; }

};

In this example, "MyClass" has a default constructor with no parameters and a parameterized constructor that takes two parameters, "xVal" and "yVal". The parameterized constructor initializes the properties "x" and "y" to the values passed as arguments.

MyClass myObject(10,20);

This creates an object of the "MyClass" class, and the parameterized constructor is called, initializing the properties "x" and "y" to 10 and 20 respectively.

It is also important to note that the default constructor has a special meaning when it comes to initialization of objects. It is used as a default initialization for a class type object. When an object of a class type is created with no initializer, the default constructor is called. However, if a class does not define a default constructor, the program will not compile.

In summary, a default constructor in C++ is a constructor that has no parameters. It is automatically called when an object of a class is created without any arguments. It is typically used to initialize the object's properties to their default values. The default constructor is a useful feature that allows you to create an object without having to explicitly specify any values for its properties.