TSelector

Class Description

                                                                        
 A TSelector object is used by the TTree::Draw, TTree::Scan,            
 TTree::Loop, TTree::Process to navigate in a TTree and make            
 selections. It contains the following main methods:                    
                                                                        
 void TSelector::Init(TTree *t). Called every time a new TTree is       
    attached.                                                           
 void TSelector::Begin(). This method is called before looping on the   
    events in the Tree. The user can create his histograms in this      
    function. When using PROOF Begin() is called on the client only.    
    Histogram creation should preferable be done in SlaveBegin() in     
    that case.                                                          
 void TSelector::SlaveBegin(). This method is called on each PROOF      
    worker node. The user can create his histograms in this method.     
    In local mode this method is called on the client too.              
                                                                        
 Bool_t TSelector::Notify(). This method is called at the first entry   
    of a new file in a chain.                                           
                                                                        
 Bool_t TSelector::Process(Long64_t entry). This method is called       
    to process an event. It is the user's responsability to read        
    the corresponding entry in memory (may be just a partial read).     
    Once the entry is in memory one can apply a selection and if the    
    event is selected histograms can be filled. Processing stops        
    when this function returns kFALSE. This function combines the       
    next two functions in one, avoiding to have to maintain state       
    in the class to communicate between these two funtions.             
    See WARNING below about entry.                                      
    This method is used by PROOF.                                       
 Bool_t TSelector::ProcessCut(Long64_t entry). This method is called    
    before processing entry. It is the user's responsability to read    
    the corresponding entry in memory (may be just a partial read).     
    The function returns kTRUE if the entry must be processed,          
    kFALSE otherwise. This method is obsolete, use Process().           
    See WARNING below about entry.                                      
 void TSelector::ProcessFill(Long64_t entry). This method is called     
    for all selected events. User fills histograms in this function.    
    This method is obsolete, use Process().                             
    See WARNING below about entry.                                      
 void TSelector::SlaveTerminate(). This method is called at the end of  
    the loop on all PROOF worker nodes. In local mode this method is    
    called on the client too.                                           
 void TSelector::Terminate(). This method is called at the end of       
    the loop on all events. When using PROOF Terminate() is call on     
    the client only. Typically one performs the fits on the produced    
    histograms or write the histograms to file in this method.          
                                                                        
 WARNING when a selector is used with a TChain:                         
    in the Process, ProcessCut, ProcessFill function, you must use      
    the pointer to the current Tree to call GetEntry(entry).            
    entry is always the local entry number in the current tree.         
    Assuming that fChain is the pointer to the TChain being processed,  
    use fChain->GetTree()->GetEntry(entry);

void Abort(const char *why, EAbort what)

 Abort processing. If what = kAbortProcess, the Process() loop will be
 aborted. If what = kAbortFile, the current file in a chain will be
 aborted and the processing will continue with the next file, if there
 is no next file then Process() will be aborted. Abort() can also  be
 called from Begin(), SlaveBegin(), Init() and Notify(). After abort
 the SlaveTerminate() and Terminate() are always called. The abort flag
 can be checked in these methods using GetAbort().

TSelector * GetSelector(const char *filename)

 The code in filename is loaded (interpreted or compiled, see below),
 filename must contain a valid class implementation derived from TSelector.

 If filename is of the form file.C, the file will be interpreted.
 If filename is of the form file.C++, the file file.C will be compiled
 and dynamically loaded. The corresponding binary file and shared
 library will be deleted at the end of the function.
 If filename is of the form file.C+, the file file.C will be compiled
 and dynamically loaded. At next call, if file.C is older than file.o
 and file.so, the file.C is not compiled, only file.so is loaded.

 The static function returns a pointer to a TSelector object

TSelector

class TSelector : public TObject

Data Members

Class Description