C++ Constant Array of Member Function Pointers

Question

I have looked at a lot of posts on arrays of member function pointers, but none that quite answer exactly for me. This is an embedded application, with no functional or dynamic allocation.

Basically I want a constant (in flash program memory) array of structures, each of which contain some member function pointers to private members. I would prefer not to manually specify the size of the array.

I have simplified it down to this example. This does not compile due to constexpr evaluation before class definition is complete. I am guessing this means before the class "Example" definition is incomplete.

Can someone please help show me how I could achieve this? Preferably without any complex programming if possible.

#include <array>

class Example
{
    private:

    bool SetOne(const char * strVal);
    bool SetTwo(const char * strVal);
    
    struct Param
    {
        using SetValueFunc = bool (Example::*)(const char * strVal);
        constexpr Param(const char * n, SetValueFunc s) : Name(n), SetValue(s) {}
        const char * Name;
        SetValueFunc SetValue;
    };

    static constexpr std::array cSupportedParameters =
    {
        Param("One", &Example::SetOne),
        Param("Two", &Example::SetTwo)
    };
};

Answer 1

Instead of using an array for this, you can define a function that returns the array:

static constexpr std::array<Param, 2> cSupportedParameters()
{
    return {
        Param("One", &Example::SetOne),
        Param("Two", &Example::SetTwo)
    };
}

As for deducing the array size automatically, I can't think of a clean way to do that. At least if you get the count wrong with respect to how many entries are in the initializer list, it will result in a compilation error. So it should be simple to keep this up to date when you add methods.