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AGM::LibReflection: A reflection library for C++.

Introduction

LibReflection is a little library (well, a header to be specific) that gives reflection capabilities to C++ classes. When we talk about reflection, we don't mean just RTTI, but a rich palette of capabilities useful in every day programming:

  • specify and examine class inheritance
  • declare and examine normal and static fields
  • declare and examine normal, virtual, and static methods
  • declare and use properties and events
  • set and get field values
  • call methods and get results
  • create instances without having the headers at hand, by using a class registry

And all the above almost happen automatically, with very few macros that the programmer has to put in the application's classes...and you also get the added benefit of class properties and events, something that C++ does not provide by default.

Demo

Using LibReflection is very easy. The following piece of code shows a class with fields, properties and methods, all reflected in the class' Class object:

//what you need to include
#include "reflection.hpp"


//namespace usage
using namespace agm::reflection;


//example base class
class Base {
public:
    //needed so as that the class gets reflection capabilities
    CLASS(Base, NullClass);

    //a reflected property
    PROPERTY(int, length);

    //a reflected method
    METHOD(public, bool, processLength, (int l));

private:
    //a reflected field
    FIELD(private, int, m_length);

    //property getter
    int get_length() const {
        return m_length;
    }

    //property setter
    void set_length(int l) {
        m_length = l;
    }
};


//a reflected method implementation
bool Base::processLength(int l)
{
    return l == m_length;
}


//a derived class
class Derived : public Base {
public:
    //derived reflected class
    CLASS(Derived, Base);
};


//for the demo
#include <iostream>
using namespace std;


int main()
{
    //a class instance
    Derived derived;

    //get the class of the Derived class
    const Class &derived_class = derived.getClass();

    //print the class name
    cout << derived_class.getName() << endl;

    //print the the m_length field
    const Field &length_field = derived_class.getField("m_length");
    cout << length_field.getType() << " " 
         << length_field.getName() << endl;

    //print the the length property
    const Property &length_prop = derived_class.getProperty("length");
    cout << length_prop.getType() << " " 
         << length_prop.getName() << endl;

    //print the 'processLength()' method
    const Method &process_length_method = 
                 derived_class.getMethod("processLength");
    cout << process_length_method.getType() << " "
         << process_length_method.getName()
         << process_length_method.getArgs()
         << endl;

    //set the length property
    cout << "using length property" << endl;
    length_prop.set(&derived, 10);
    int i;
    length_prop.get(i, &derived);
    cout << "length = " << i << endl;

    //calling the length method
    cout << "calling bool Base::processLength(int)" << endl;
    bool b;
    process_length_method.invoke(b, (Base *)&derived, 10);
    cout << "processLength=" << b << endl;

    getchar();
    return 0;
}

Documentation

For more information, you can check out my little site here.


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