Delegates para validação automágica

validator.cpp

#include <iostream>
#include <string>
#include <vector>
#include <typeinfo>
#include <sstream>

using namespace std;

namespace Validation
{
    namespace ValidationStatus
    {
        enum EStatus
        {
            Failed = -1,
            Success = 0,
            Ignored = 1
        };
    }

    struct ValidationResult
    {
        ValidationStatus::EStatus status;
        string reason;
    };

    class Element { };

    typedef ValidationResult (*ValidationFunction)(const Element &);

    typedef void (*Block)(const vector<ValidationFunction>::iterator &);

    class Validator: public vector<ValidationFunction>
    {
    public:
        Validator &
        operator+=(const ValidationFunction & func)
                {
            this->push_back(func);
            return *this;
        }
        void
        each(const Block & block)
                {
            for (auto elem = this->begin(); elem < this->end(); elem++)
                block(elem);
        }
    };
}

Validation::ValidationResult foo(const Validation::Element & e)
{
    return {Validation::ValidationStatus::Failed, "Falhou"};
}

Validation::ValidationResult bar(const Validation::Element & e)
{
    return {Validation::ValidationStatus::Ignored, "Ignorado"};
}

Validation::ValidationResult baz(const Validation::Element & e)
{
    return {Validation::ValidationStatus::Success, "Sucesso"};
}

namespace Validation
{
    static Validation::Validator validator;
}

Validation::Validator &
getValidator() {
    return Validation::validator;
}

int main()
{
    getValidator() += foo;
    getValidator() += bar;
    getValidator() += baz;
    for (auto i = 0; i < 10; i++)
        getValidator() += [] (const Validation::Element & e) -> Validation::ValidationResult {
            static int j; j >= 0 ? ++j : j; stringstream s; s << "Lambda #"; s << j;
            return {Validation::ValidationStatus::Success, s.str() };
        };

    getValidator().each([] (const Validation::Validator::iterator & it) {
        cout << (*it)(Validation::Element()).reason << endl;
    });

    return 0;
}