Discussion :

[Florian Goo]

Bonjour à tous,

J'aimerais factoriser plusieurs classes de mon projet qui présentent une structure similaire.
Voici à quoi elles ressemblent (en pseudo-code, pour être plus clair) :

Code :

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struct access_specifier
{
    enum type
    {
        PUBLIC,
        PROTECTED,
        PRIVATE
    };
 
    value value_;
};

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struct built_in_type_specifier
{
    enum type
    {
        CHAR,
        WCHAR_T,
        BOOL,
        SHORT,
        INT,
        LONG,
        SIGNED,
        UNSIGNED,
        FLOAT,
        DOUBLE,
        VOID
    };
 
    type type_;
};

Afin de les factoriser, j'aimerais créer une classe template dans ce style :

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template<const char** StringList>
class string_enumeration
{
    public:
        string_enumeration(const std::string& value);
 
        const char*
        get_value() const;
 
    private:
        static const char** string_list_; //on aura string_list_ = StringList
        int value_index_; //index dans le tableau de char*
};

Pour avoir un équivalent de access_specifier, on fera ceci (enfin, on aimerais bien faire ceci, justement ) :

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const char* access_specifier_string_list[] = {"public", "protected", "private", ""};
 
typedef string_enumeration<access_specifier_string_list> access_specifier;

Ainsi, on créera un access_specifier de cette façon :

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access_specifier an_access_specifier("public");

Si "public" ne fait pas partie de la liste de char*, on balancera une exception ou un assert… mais là n'est pas le problème. La classe va mémoriser l'index de la chaîne reçue (ici 0, puisque "public" est le premier élément de la liste de char*).
L'appel à get_value() n'a plus qu'à renvoyer un pointeur vers la chaîne pointée par l'index.

Le code semble se construire correctement, mais aucun binaire n'est linké. Lorsque j'essaie de construire une deuxième fois, gcc se résout à me tenir ce charmant discours :

Code :

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CMakeFiles/socoa.dir/src/socoa/cpp/declaration_syntax_analyzer.cpp.o:(.data.rel.local+0x0): first defined here
collect2: ld returned 1 exit status
make[2]: *** [lib/Debug/libsocoa.so] Erreur 1
make[1]: *** [CMakeFiles/socoa.dir/all] Erreur 2
make: *** [all] Erreur 2
Process terminated with status 2 (0 minutes, 10 seconds)
0 errors, 0 warnings

Dois-je m'en tenir à du polymorphisme dynamique pour effectuer cette factorisation ?