Loop on a ROOT file directory for several files simultaneously

[puco4]

Hi, I’m trying to generalize this code: https://root.cern.ch/root/html/tutorials/io/loopdir.C.html with the idea to read from multiple files (that have the same structure) at the same time.
I’m trying:

//Open directory in each file
 f1->cd();
 gDirectory->cd(dir);
 TDirectory* d1= gDirectory;

 f2->cd();
 gDirectory->cd(dir);
 TDirectory* d2= gDirectory;

//Read keys in the directories
 TList* key_ring1 = d1->GetListOfKeys();
 TList* key_ring2 = d2->GetListOfKeys();

//Create iterators and objects to read from
  TIter it1(key_ring1), it2(key_ring2);
  TObject *o1, *o2;

//Read different keys
 TKey* key1, key2;
 while ((key1 = (TKey*)it1())){
   key2 = (TKey*)it2();	
   o1=key1->ReadObj();
   o2=key2->ReadObj();
 }

But it does not seem to like key2 = (TKey*)it2() (no viable overloaded ‘=’). Any ideas?
Thank you.

[ganis]

Dear puco4,

@puco4

it does not seem to like key2 = (TKey*)it2()

What’s the exact error?

Did you try this?

//Read keys in the directories
TList* key_ring1 = f1->GetListOfKeys();
TList* key_ring2 = f2->GetListOfKeys();

//Create iterators and objects to read from
TIter it1(key_ring1), it2(key_ring2);
TObject *o1, *o2;

//Read different keys
TKey* key1, key2;
while ((key1 = (TKey*)it1()) && (key2 = (TKey*)it2())){
    o1 = key1->ReadObj();
    o2 = key2->ReadObj();
}

G Ganis

[puco4]

Hi Ganis, thank you for your answer.
Yes, that was the first thing I tried.
I have also tried a for loop:

for(key1 = (TKey*) it1(), key2 = (TKey*) it2(); key1!=NULL; key1 = (TKey*) it1(), key2 = (TKey*) it2()){
}

In all cases I get this error:

error: no viable overloaded '='
  while ((key1 = (TKey*)it1()) && (key2 = (TKey*)it2())){
                                   ~~~~ ^ ~~~~~~~~~~~~
/opt/root/include/TKey.h:31:10: note: candidate function not viable: no known co
nversion from 'TKey *' to 'const TKey'
      for 1st argument; dereference the argument with *
   TKey& operator=(const TKey&); // TKey objects are not copiable.
         ^

[puco4]

Ah, I was just doing an error and I did not realize, sorry to bother you.
TKey* key1, key2; should have been TKey *key1, *key2;.