const variables in constructor

[adam2016]

hey guys I have a const variable in my year class and I want to initialise it when the class is created but for some reason when I try this I get an error

is there anyway you can initialise const variables in a constructor?

I also can't give it a default value in its header.

  #ifndef YEAR_H
#define YEAR_H


class Year
{
    public:
        Year();
        Year(int x);
        virtual ~Year();

    protected:

    private:
        const int y;
};

#endif // YEAR_H

#include "Year.h"

Year::Year()
{



}


Year::Year(int x)
: y(x)
{
    //ctor
}

Year::~Year()
{
    //dtor
}

C:\Users\User\control\main.cpp|10|error: uninitialized const member in 'const int' [-fpermissive]|

[adam2016]

another example

#ifndef YEAR_H
#define YEAR_H

class Year
{
    public:
        const int mac = 2018;

        Year();
        Year(int x);
        virtual ~Year();

    protected:

    private:
        int y;

};

#endif // YEAR_H

how in the heck do you declare a const variable or type??

when doing it in one .cpp file(all closses and functions in one file) it works fine but it seems like it is impossible to declare a const in a class

[chicofeo]

You could use static like, static const int mac = 2018;


https://stackoverflow.com/questions/14495536/how-to-initialize-const-member-variable-in-a-class

[keskiverto]

You seem to be almost there:

#include <iostream>

class Year
{
    public:
        Year();
        Year(int);
        Year(int, float);
        virtual ~Year();
        const float pi {3.14}; // C++11 allows initializer in definition

    protected:

    private:
        const int y;
};

int main()
{
  Year one;
  Year two( 7, 2.7 );
  Year three( 13 );
}

Year::Year()
 : y(42) // must initialize the const to some default
{
}

Year::Year(int x)
 : y(x)
{
}

Year::Year(int x, float f)
 : pi(f), y(x)
{
}

Year::~Year()
{
}