[SOLVED] Can a class internally monitor its member function usage and arguments

Issue

Is it possible for a class to monitor when its member function is called and the arguments provided to the function, without modifying the member functions? I have a class defined and I want to have the option to toggle such functionality without modifying the functions themselves. At the end of the objects lifetime I would like to output this information to a log file somewhere.

Solution

If you cannot change the original class you can instead write an adapter which does the logging for you.

Example:

#include <iostream>
#include <map>

class ProfilingSummary
{
public:
    static ProfilingSummary& Instance()
    {
        static ProfilingSummary myInstance;
        return myInstance;
    }

    void Log(const std::string& method)
    {
        auto result_pair = Results.insert(std::make_pair(method, 1));
        if(!result_pair.second)
        {
            // method already inserted
            auto& count = result_pair.first->second;
            count++;
        }
    }

    ProfilingSummary(ProfilingSummary const&) = delete;             // Copy construct
    ProfilingSummary(ProfilingSummary&&) = delete;                  // Move construct
    ProfilingSummary& operator=(ProfilingSummary const&) = delete;  // Copy assign
    ProfilingSummary& operator=(ProfilingSummary&&) = delete;       // Move assign

private:
    ProfilingSummary() = default;
    
    ~ProfilingSummary()
    {
        std::cout << std::endl;
        std::cout << "Profiling Summary: " << std::endl;
        for(const auto& result : Results)
        {
            const auto method = result.first;
            const auto count = result.second;
            std::cout << method << 
                " called " << count << std::endl;
        }
    }

    std::map<std::string, int> Results;
};

struct Original
{
    void Foo() { std::cout << "Hello World" << std::endl; }
};

struct OriginalAdapter
{
    void Foo() 
    {
        ProfilingSummary::Instance().Log(__FUNCTION__); // use symbol for function name, you can copy this for each method
        _Original.Foo();
    }

private:
    Original _Original;
};

int main()
{
    OriginalAdapter original;
    original.Foo();
}

Output:

Hello World

Profiling Summary: 
Foo called 1

Answered By - RoQuOTriX