dispatchDynamicPolymorphism.cpp

#include <chrono>
#include <iostream>

auto start = std::chrono::steady_clock::now();

void writeElapsedTime()
{
    auto now = std::chrono::steady_clock::now();
    std::chrono::duration<double> diff = now - start;
    std::cerr << diff.count() << " sec. elapsed: ";
}

struct MessageSeverity{
    virtual void writeMessage() const
    {
        std::cerr << "unexpected" << '\n';
    }
};

struct MessageInformation: MessageSeverity{
    void writeMessage() const override{
        std::cerr << "information" << '\n';
    }
};

struct MessageWarning: MessageSeverity{
    void writeMessage() const override{
        std::cerr << "warning" << '\n';
    }
};

struct MessageFatal:MessageSeverity{};

void writeMessageReference(const MessageSeverity& messServer)
{
    writeElapsedTime();
    messServer.writeMessage();
}

void writeMessagePointer(const MessageSeverity* messServer)
{
    writeElapsedTime();
    messServer->writeMessage();
}


int main()
{
    std::cout <<'\n';
    MessageInformation messInfo;
    MessageWarning messWarn;
    MessageFatal messFatal;

    MessageSeverity& messRef1 = messInfo;
    MessageSeverity& messRef2 = messWarn;
    MessageSeverity& messRef3 = messFatal;

    writeMessageReference(messRef1);
    writeMessageReference(messRef2);
    writeMessageReference(messRef3);

    std::cerr << '\n';

    MessageSeverity* messP1 = new MessageInformation;
    MessageSeverity* messP2 = new MessageWarning;
    MessageSeverity* messP3 = new MessageFatal;

    writeMessagePointer(messP1);
    writeMessagePointer(messP2);
    writeMessagePointer(messP3);

    std::cout << '\n';

    return 0;

}