Creating An Immutable Object

An immutable object is an object that once gets created can no longer changed its state afterwards.

For example, to make a class immutable we can do the following:

class A

{

//1. we make its attributes private.

int x,y;

public:

//2. only create getters if needed, no setters of course

int getx() const {return x;} //same for y

public:

//3. declare an explicit constructor

explicit A(int _x, int _y) : x(_x), y(_y){}

};

We make the attributes private so derived classes cannot change the state. Of course, getters should return copies not references to the attribute.