Problem using CompareTo function with TString from TTreeReader

[NikkieD]

Hi Everyone,

I’m trying to read two trees in the same file with TTreeReader. In one of the trees there is a TString branch that I want to use to make a selection, so I wanted to use the CompareTo() function of the TString, but I can’t make it work…

So here is what I’m doing:

#include <iostream>

#include "TFile.h"
#include "TTreeReader.h"

void rd53aCorrelation ( ) { 

  TFile *file = TFile::Open ( "telescopeData.root" ) ;

  TTreeReader dutReader ( "dutData", file ) ;
  TTreeReader telReader ( "cluster3DTree", file ) ;

  // Declare telescope values
  TTreeReaderValue<TString> myM3226( telReader, "modName") ;
  TTreeReaderValue<Int_t> telEvent( telReader, "event" ) ;
  TTreeReaderValue<Double_t> telY( telReader, "y" ) ;

  // Declare dut values
  TTreeReaderValue<Int_t> dutEvent( dutReader, "trigNumber") ;
  TTreeReaderValue<Int_t> rowDUT( dutReader, "row") ;

  TH2D *corr = new TH2D("corr", "Correlation between RD53A and M3226", 480, -3., 3., 200, -0.8, 0.8);

  // Now we loop
  while ( telReader.Next() ) {

    if ( *myM3226.CompareTo("M3226") != 0 ) {

      while ( dutReader.Next()  ) { 

        if ( *telEvent < *dutEvent ) break ;
        if ( *telEvent != *dutEvent ) continue ;
        else if ( *telEvent == *dutEvent ) {

          //corr->Fill( (Double_t)( *rowDUT * 0.005-0.5), *telY );
          std::cout << *rowDUT << std::endl;
        }//end else
      }//end while
    }//end if m3226
  }//end whil 

corr->Draw("colz");

}//end void

The problem is with the line where I compare the TString to see if it matches “M3226”. There I get the error:

/Users/nikkie/cernbox/myWork/telescope/rd53aOctober2018/dataAnalysis/rd53aCorrelation.cc:27:18: error: no member named 'CompareTo' in 'TTreeReaderValue<TString>'; did you mean to use '->' instead of '.'?
    if ( *myM3226.CompareTo("M3226") != 0 ) {
                 ^
                 ->
/Users/nikkie/cernbox/myWork/telescope/rd53aOctober2018/dataAnalysis/rd53aCorrelation.cc:27:10: error: indirection requires pointer operand ('int' invalid)
    if ( *myM3226.CompareTo("M3226") != 0 ) {

I used the arrow as well to get rid of the first error but I can never get rid of the second one.

Does anybody know what I’m doing wrong?

Cheers,
Nikkie

---

_ROOT Version: 6.14/04
_Platform: MacOS Mojave
_Compiler: XCode

---

[eguiraud]

Hi,
I think the right C++ is myM3226->CompareTo("M3226") != 0: a -> to call CompareTo on the TString pointed by myM3226, and no * as you don’t need to dereference an int.

Cheers,
Enrico

[behrenhoff]

When just checking for equality, you should prefer operator== over CompareTo. (better readability, less work)
So simply if (*myM3226 == "M3226") ...

For whatever reason the arrow isn’t working for me:

root [21] (*myM3226).CompareTo("X")
(int) 1
root [22] myM3226->CompareTo("X")
ROOT_prompt_22:1:8: error: member reference type 'TTreeReaderValue<TString>' is not a pointer; did you mean to use '.'?
myM3226->CompareTo("X")
~~~~~~~^~
root [23] (*myM3226 == "hello")
(bool) true

[NikkieD]

Hi Both,

Thanks for the help!
Actually Eguiraud’s comment solved my issue. I get a different error now but that is because my file is messed up.

Thanks again!
Nikkie