How can I make a type safe string "definition" object in C++?

Question

I like using enum class to avoid hard coded values as much as possible but it's a little bit more complicated when it comes to strings. I have a design I'd like to share that I feel is a little bit bulky and I would love some ideas on how to simplify it.

class StringDefinition
{
private:
   StringDefinition(const std::string &def);

public:
    bool operator==(const StringDefinition&rhs) const;

public:
   static const StringDefinition StringDefinitionOne;
   static const StringDefinition StringDefinitionTwo;
   static const StringDefinition StringDefinitionThree;

public:
   std::string ToString() const;

private:
   string stringDef;
};

StringDefinition::StringDefinition(const std::string &stringDef)
{
   this->stringDef = stringDef;
}

const StringDefinition StringDefinition::StringDefinitionOne("One");

etc...

All ideas and comments are welcome.

Edit: I am not using string literals because it does not force the developer to use a value from a definition list. They can still hard code a string even when you expect them to use your string literal. If I'm doing something crazy, I'd love some constructive criticism rather than just down voting the question.

What does this bring over just a named global string literal? — Borgleader, Jan 31 '17 at 20:44
I don't want to just make an object with const strings because then the type is string. Anyone can still hard code a string. Say I create a method and I want a StringDefinition passed in, I can do that. If I use a string literal, someone can pass a hard coded string — Pittfall, Jan 31 '17 at 20:44
@Pitfall what's to prevent someone from making their own StringDefinition and passing it in? — Anon Mail, Jan 31 '17 at 20:47
@AnonMail They can do this but now they are making a conscious decision to modify a library. With a string literal, a developer may not be aware that it exists. — Pittfall, Jan 31 '17 at 20:50
Use enums to enforce values. Input strings from the external world (e.g. files or database) should be converted to/from enums. — Anon Mail, Jan 31 '17 at 20:54
@AnonMail you cannot use an enum for strings so you'd need a mapping database table that has an id and a value. Sure, if you want to dig deep, you can argue the database design but it would take an arrogant newbie to suggest a rewrite. Not saying this is you, I'm just saying that perfecting the design is not always an option. — Pittfall, May 05 '17 at 16:25

score 0 · Answer 1 · answered Jan 31 '17 at 20:48

This is question of personal taste, but how about keeping it a little more simple; something along the lines of:

enum class Foo { Ack, Eek };

explicit operator std::string(Foo foo) {
    static const char* const names[] = { "Ack", "Eek" };
    return names[(int)foo];
}

How can I make a type safe string "definition" object in C++?

1 Answers1