How Can I Define Private Static Constant String Data Members in C ?

Achieving Static Const String Data Members: A Comprehensive Guide

In the pursuit of defining private static constant strings for classes, such as shape factories, you may encounter a roadblock with C compilers. This is due to restrictions imposed by the C standard. To overcome this challenge and establish a static const string data member, consider the following solutions:

Inline Variables (C 17 and Later)

Utilizing inline variables, introduced in C 17, provides a convenient and efficient way to define static const variables:

class A {   
private:      
  inline static const string RECTANGLE = "rectangle";
};

External Definition and Initialization

Pre-C 17 versions necessitate defining the static member outside the class and providing the initializer separately:

class A {   
private:      
  static const string RECTANGLE;
};

const string A::RECTANGLE = "rectangle";

It's important to note that the syntax with an initializer inside the class definition is reserved for integral and enum types only.

A Word on #define

While #define may seem tempting for defining constants, it introduces a level of global visibility that may not be desirable. For instance, if the constant is defined in a header file, it will become globally accessible to all parts of the program. This can lead to naming conflicts with different implementations defining the same constant, among other potential issues.

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