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

, 1 Nov 2004
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Description of the library AGM::LibReflection.

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.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Achilleas Margaritis
Software Developer (Senior)
Greece Greece
No Biography provided

Comments and Discussions

 
Generaltypeless parameters PinmemberMember 1811246-Oct-08 5:26 
GeneralWindows CE compilation PinmemberDuvidaCruel9-Feb-07 9:11 
GeneralLibReflection for gcc PinsussAnonymous3-May-05 4:51 
QuestionArrays? Pinmemberneo26007776-Apr-05 9:30 
GeneralAn Update Version Posted Pinmembermy203829-Mar-05 7:52 
GeneralNew Changes Made to LibReflection Pinmembermy203823-Mar-05 10:22 
GeneralRe: New Changes Made to LibReflection PinmemberWREY28-Mar-05 0:14 
GeneralRe: New Changes Made to LibReflection Pinmembermy203828-Mar-05 6:40 
GeneralNot totally true. PinmemberWREY28-Mar-05 8:23 
GeneralRe: Not totally true. Pinmembermy203829-Mar-05 7:53 
GeneralCompile Error in VS.NET 1.1 Pinmembercolormegjian22-Mar-05 3:26 
GeneralRe: Compile Error in VS.NET 1.1 Pinmembertomthorne22-Apr-05 7:23 
GeneralRe: Compile Error in VS.NET 1.1 Pinmemberderchoff6-Oct-05 0:15 
QuestionCan i use it in BCB? PinmemberFlameBlade17-Feb-05 2:41 
GeneralContact Pinsusspsyclonist (Stephan K.)22-Nov-04 1:41 
QuestionCan Instance be Created Dynamicly? PinmemberLaisser21-Nov-04 6:21 
GeneralVery Interesting! Pinmemberggerules10-Nov-04 5:19 
GeneralCool! PinmemberJim Crafton2-Nov-04 14:15 
GeneralRe: Cool! Pinmemberaxilmar3-Nov-04 2:37 
GeneralRe: Cool! Pinmembermy203815-Mar-05 10:27 
GeneralDude Pinmemberarmentage2-Nov-04 9:23 
GeneralRe: Dude Pinmemberaxilmar2-Nov-04 9:42 
GeneralRe: Dude PinmemberDave Handley3-Nov-04 6:10 
GeneralRe: Dude PinmemberAnders Dalvander13-Nov-04 2:03 
Dave Handley wrote:
1) Immature libraries. Because the languages haven't been around very long, the libraries have a huge number of weaknesses - the last time I tried to use C# I found that I couldn't create a directory browser from the file dialog since the file dialog didn't include that feature and it was a final class. In C++ I would simply inherit off CFileDialog.
 
CFileDialog isn't really standard C++, it is a MFC class, and thus will only work in Microsoft Windows. But should't you use the Win32 function SHBrowseForFolder, and not derive from CFileDialog anyway?
 
Dave Handley wrote:
2) The syntax is impenetrable. Managed C++ has improved slightly with the newer work Microsoft has done, but it is still nowhere near as clear as well written C++.
 
True, Managed C++ wasn't very neat to use, and that is why C++/CLI[^] was developed. C++/CLI is as penetrable as standard C++, atleast when you are doing the same thing. I wouldn't state that standard C++ is clear, either.
 
Dave Handley wrote:
3) The syntax is non-standard. Except in the rare cases where the CLR exists for other platforms and compilers, you are stuck with VC++ and Windows.
 
The CLR, CLI, C# and C++/CLI are standards, but you're stuck in .NET, that is true. But .NET is ported to other systems than Windows. See DotGnu[^] and Mono[^].
 
Dave Handley wrote:
4) The CLR is incredibly slow compared to raw C++. Because you are working through an intermediate language, and you have the overhead of garbage collection and smart pointers, for time critical applications Managed C++ just doesn't hold up. I write CAD applications for a living and Managed C++ just wouldn't cut it.
 
You are not working through an intermediate language, the JIT-compiler will create machine code. In C++/CLI you don't have to use garbage collection, you can use deterministic destruction instead.
Vertigo Software ported Quake 2[^] to .NET with a performance decrease of only 15%. And that was done in 5 days: 4 days for porting from C to C++ and one day to port to Managed C++.
GeneralRe: Dude PinmemberDave Handley13-Nov-04 3:08 

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