Using static const char* const instead of #define

Question

I get the error error: ‘Name’ was not declared in this scope What am I missing here.

Source File:

#include<iostream>
#include "scr.h"
using namespace std;

const char* const Test::Name;  

void Test::Print()
{
    cout<<Name;
}

int main()
{       
    Test *t = new Test();
    t->Print();
    delete t;   
}

Header File:

class Test
{   
    static const char* const Name = "Product Name";
    public:
        void Print();
};

EDIT:

If I replace char* const with int, it works. Why?

static const int Name = 4; //in header

const int Test::Name;  //In source

The purpose of the code is to have an alternate for #define as mentioned in Effective C++. In the example there, static const int is used.

krammer · Accepted Answer · 2011-09-30 04:49:48Z

3

You cannot initialize a static member variable within a class. Not even in the header file.

Header File:

class Test
{   
    static const char* const Name;
    public:
        void Print();
};

In your cpp file:

const char* const Test::Name = "Product Name";

Edit: I must have added that the initialization is allowed only for int and enumerations and that too with constants that can be evaluated at compile time.

edited Sep 30, 2011 at 4:49

answered Sep 30, 2011 at 4:36

krammer

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Comments

KV Prajapati · Accepted Answer · 2011-09-30 04:40:23Z

2

You can't initialize members in class definition.

Take a look at Parashift post - Can I add = initializer; to the declaration of a class-scope static const data member?

SUMMARY: The caveats are that you may do this only with integral or enumeration types, and that the initializer expression must be an expression that can be evaluated at compile-time: it must only contain other constants, possibly combined with built-in operators.

edited Sep 30, 2011 at 4:40

answered Sep 30, 2011 at 4:31

KV Prajapati

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2 Comments

KV Prajapati Over a year ago

@cod3r - Read the link I've posted.

KV Prajapati Over a year ago

@cod3r -Thanks! Glad you got it useful. I'm a big admirer of ParaShift.

Vaughn Cato · Accepted Answer · 2011-09-30 04:51:38Z

1

In general, you can't initialize static variables directly in the class definition, you have to do it in a separate source file, like this:

const char* const Test::Name =  "Product Name";

An exception is integral constants, which are allowed to be in the class definition. An easy workaround is to use a static member function instead:

struct Test {
  static const char *Name() { return "Product Name"; }
};

edited Sep 30, 2011 at 4:51

answered Sep 30, 2011 at 4:31

Vaughn Cato

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Comments

Dominik Grabiec · Accepted Answer · 2011-09-30 04:32:12Z

0

Move the assignment of the string to the source/implementation file (.cpp).

answered Sep 30, 2011 at 4:32

Dominik Grabiec

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