CODEWITHSUNDEEP
c++classconstants
Rdou
Rdou

Reputation: 219

void Test::printxy(void)' : cannot convert 'this' pointer from 'const Test' to 'Test &' in const class

I have write a very simple program about const class, however, when I compile, there is a error:void Test::printxy(void)' : cannot convert 'this' pointer from 'const Test' to 'Test &'

The program is as below

#include <iostream>
using namespace std;
class  Test
{
private:
    int x, y;
public:
    Test(int a = 1, int b = 1) : x(a), y(b) {};
    void printxy();
};
void Test::printxy()
{
    cout << "x*y=" << x*y << endl;
}
void main(void)
{
    const Test t;
    t.printxy();
    system("pause");
}

Upvotes: 1

Views: 243

Answers (2)

Dietmar K&#252;hl
Dietmar K&#252;hl

Reputation: 153955

You try to call the non-const function printxy() on the const obejct t. You are missing a const after the method declaration:

class Test {
    // ...
    void printxy() const;
};

void Test::printxy() const {
    // ...
}

Upvotes: 1

Kerrek SB
Kerrek SB

Reputation: 477358

Since the printxy member function is not declared const, it cannot be invoked on a constant object. You need to declare the member function const like this:

class Test
{
    void printxy() const;
    //             ^^^^^

    // ...
};

void Test::printxy() const
{
    // ...
}

Upvotes: 3

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