C ++, const:, const

C ++, const:, const

Problem:

• Can a const member function and a common member function have the same parameter name? Yes. This is a function overload.
• Can a const member function modify the value of a member variable of an object? It cannot be modified. // Error C3490: Unable to modify because the constant object is accessing "year"
• Can non-const member functions access const object members? Not accessible. // Error C2662: "Time: show_time": the "this" pointer cannot be converted from "const Time" to "Time &"
• Can a const member function call a non-const member function? No.
• Can the const member function access non-const member variables? Yes.

1. const member functions and common member functions can be the same parameters with the same name, which is a function overload.

# Include "stdafx. h"

# Include <iostream>

Using namespace std;

Class Time

{

Public:

Time (): year (2015)

{

}

Void show_time (void) const

{

Cout <"year:" <year <endl;

}

Void print (int I)

{

Cout <"fun I:" <I <endl;

}

Void print (int I) const

{

Cout <"const fun I:" <I <endl;

}

Private:

Const int year;

};

Int _ tmain (int argc, _ TCHAR * argv [])

{

Time time;

Time. show_time ();

Time. print (1 );

Time const ctime;

Ctime. show_time ();

Ctime. print (1 );

System ("pause ");

Return 0;

}

/*

Annual: 2015

Annual: 2015

Press any key to continue...

*/

2. the const member function cannot modify the value of the member variable of the object.

Class Time

{

Public:

Void show_time (void) const

{

Cout <"year:" <year <endl;

Year = 11; // error C3490: Unable to modify because the constant object is accessing "year"

}

Private:

Int year;

};

3. Non-const member functions cannot access const object members:

4. Const member functions cannot call non-const member functions;

Class Time

{

Public:

Time (): year (2015)

{

}

Void show_time (void) const

{

Cout <"year:" <year <endl;

Print (11); // error C2662: "Time: print": the "this" pointer cannot be converted from "const Time" to "Time &"

}

Void print (int I)

{

Cout <"fun I:" <I <endl;

}

Private:

Int year;

};

5. the const member function can access non-const member variables. But it cannot be modified.

Class Time

{

...

Void show_time (void) const

{

Cout <"year:" <year <endl;

}

...

Private:

Const int year;

};

Refer: