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CollHandle.h

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/*
 * $Id: CollHandle.h,v 1.4 2008/07/03 14:29:00 pgras Exp $
 */

#ifndef EcalDigis_CollHandle_h
#define EcalDigis_CollHandle_h

#include "FWCore/ParameterSet/interface/InputTag.h"
#include "FWCore/Framework/interface/Event.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"

template<class T>
class CollHandle {
  //constructor(s) and destructor(s)
public:
  CollHandle(const edm::InputTag& tag,
             bool failIfNotFound = true,
             bool notFoundWarn = true): tag_(tag),
                                        currentColl_(&emptyColl_),
                                        notFoundAlreadyWarned_(false),
                                        failIfNotFound_(failIfNotFound),
                                        notFoundWarn_(notFoundWarn){}
  
  //method(s)
public:
  void read(const edm::Event& event){
    //    try{
    edm::Handle<T> hColl;
    event.getByLabel(tag_, hColl);
  
    //If we must be tolerant to product absence, then
    //we must check validaty before calling Handle::operator*
    //to prevent exception throw:
    if(!failIfNotFound_     // product-not-found tolerant mode
       && !hColl.isValid()){// and the product was not found
      if(notFoundWarn_
         && !notFoundAlreadyWarned_){//warning logged only once
        edm::LogWarning("ProductNotFound") << tag_
                                           << " product was not found!";
        notFoundAlreadyWarned_ = true;
      }
      currentColl_ = &emptyColl_;
    } else {
      currentColl_ = &(*hColl);
    }
  }

  
  const T* operator->() const{ return currentColl_;}

  const T& operator*() const { return *currentColl_;}
  
private:

  //attribute(s)
protected:
private:
  const edm::InputTag tag_;

  const T* currentColl_;

  const T emptyColl_;

  bool notFoundAlreadyWarned_;

  bool failIfNotFound_;

  bool notFoundWarn_;
};

#endif

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