如何将带有“ any”枚举的std :: map传递给函数

Question

I have many enum declarations like

typedef enum {
    E_FOO_1,
    E_FOO_RANDOM,
    E_FOO_25,
} E_FOO;


typedef enum {
    E_BAR_RANDOM,
    E_BAR_SOMETHING,
    E_BAR_WHATEVER,
} E_BAR;

and I need a mapping to strings

std::map<E_FOO, const char*> fooMap = {
    {E_FOO_1, "completly different string"},
    {E_FOO_RANDOM, "hi"},
    {E_FOO_25, "down"},
};
std::map<E_BAR, const char*> barMap = {
    {E_BAR_RANDOM, "1234"},
    {E_BAR_SOMETHING, "3},
    {E_BAR_WHATEVER, "45"},
};

Is there anyway to write a function which takes something like (uint8_t someEnumValue, std::map<any, const char*>) and simply returns the string?

In the real application the structure is much more complicated and the enums are handled by some C-code, which has no problem to handle the enum values as int or uint8_t but I am not very used to C++, so I see no way to pass these parameters to a general function.

Could it be done by using templates? And wouldn't that blow up the compiled code since for every enum the function needs to be compiled (the function would be in a bigger class, so I would need to template the whole class).

Thanks!

Answer 1

You can use a function template to accept any std::map whose value type is const char* :

template <typename Enum>
const char* get_string(std::uint8_t v, const std::map<Enum, const char*>& m)
{
    return m.at(static_cast<Enum>(v));
}

live example on godbolt.org