2007 Sep 09 - Sun

VC++ MultiCast Delegate Template

In follow up to my article on Fast Delegates back in June, I used the C++ STL (Standard Template Library) to create a simple, one parameter Multicast Delegate for C++. The code provided here provides a mechanism for creating a Multicast Delegate by incorporating the FastDelegate library. I used the 'vector' template from the STL to implement dynamically adding and removing object method calls to the Delegate.

#pragma once

#include <vector>
#include "FastDelegate.h"
// http://www.codeproject.com/cpp/FastDelegate.asp

template<class RO> class Delegate {
  // RO: Return Object in call

public:
  typedef FastDelegate1<RO> OnMessageHandler;
  void Add( OnMessageHandler function );
  void Remove( OnMessageHandler function );
  bool IsEmpty();
  void operator()( RO );
protected:
private:
  std::vector<OnMessageHandler> rOnFD;
};

template<class RO> void Delegate<RO>::Add( 
OnMessageHandler function ) {
  rOnFD.push_back( function );
}

template<class RO> void Delegate<RO>::Remove( 
OnMessageHandler function ) {

  std::vector<OnMessageHandler>::iterator rOnFD_Iter;

  rOnFD_Iter = rOnFD.begin();
  while ( rOnFD.end() != rOnFD_Iter ) {
    if ( function == *rOnFD_Iter ) {
      rOnFD_Iter.erase( rOnFD_Iter );
      break;
    }
    rOnFD_Iter++;
  }
}

template<class RO> bool Delegate<RO>::IsEmpty() {
  return rOnFD.empty();
}

template<class RO> void Delegate<RO>::operator()( RO ro ) {

  std::vector<OnMessageHandler>::iterator rOnFD_Iter;

  rOnFD_Iter = rOnFD.begin();
  while ( rOnFD.end() != rOnFD_Iter ) {
    (*rOnFD_Iter)( ro );
    rOnFD_Iter++;
  }
}

// =======

// Here is a declaration of three events, with each event receiving a 
// pointer to a object with class of CIQFSymbol:

Delegate<CIQFSymbol*> OnFundamentalMessage, OnUpdateMessage, OnSummaryMessage;

// Here is how to add a delegate to the MultiCast Delegate:

pSym->OnFundamentalMessage.Add( 
  MakeDelegate( this, &CGTScalpDlg::EmitDataFundamental ) );

// EmitDataFundamental is declared with:

void EmitDataFundamental( CIQFSymbol *pSym );

// The mulicast delegate can then be invoked with:

OnFundamentalMessage( this );

// =======

Caveats: I havn't proven that Delegate's Remove method works as intended yet, but theoretically it should, as coded. Proper initialization, deconstruction cleanup, and thread safety are left as exercises for the reader.

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