C ++ regular object explanation-const keyword

ConstKeywords:

The definition object modified with const is called a constant object;

Declaring a member function modified by const is called a member function;

The declared data member modified by const is a common data member.

After a variable or object is modified by const, its value cannot be updated. Therefore, the variable or object modified by const must be initialized..

Common Object Description:A common object means that the data member value of an object cannot be changed when the object is called. A common object must be initialized and cannot be updated. Common member functions cannot be called through common objects, but can be called through common objects. A common object can only call a common member function. The declaration of common objects is as follows:

Const <Class Name> <Object Name>

<Class Name> const <Object Name>

There is no difference between the two statements.

 

1The following example is used to understand common objects:

A, Please point out the following program errors

Class {

PRIVATE:

Int W, h;

Public:

Int getarea () const

{

Return w * h;

}

Int getw () {return W ;}

Void setwh (int x, int y) {W = x, H = y ;}

A (int x, int y) {W = x, H = y ;}

A () {;} // This example cannot be omitted.

};

 

 

Void main ()

{

A A; // The non-object can be not initialized.

A. setwh (3,9 );

A const B; // a const B (3, 6) must be declared and initialized at the same time ).

B. setwh (); // if this sentence is used after the above correction, the error should be that B is a common object and a non-member function cannot be called. It cannot be changed when the value is switched. setwh ()

Cout <A. getarea () <Endl <B. getarea () <C. getarea ();

System ("pause ");

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