CERN ROOT: A function that gets the first tree out of a .root -file.

getAnyTree

TTree* getAnyTree(TDirectory* dirHandle){
  
  // Returns a pointer to a TTree from within the file. Useful if you know there is only one tree in the file, but don't knowe which and where exactly.
  // within ROOT, a TTree is a TObject and a TDirectory is a TObject. But a Tree is not a TDirectory and vice versa.

  TObject* objectHandle = NULL;
  do{
    const char* key = dirHandle->GetListOfKeys()->At(0)->GetName(); // Get the first key in the directory
    objectHandle = dirHandle->Get(key); // Get the first object.
    dirHandle =  dynamic_cast<TDirectory*> (objectHandle);  // try to cast object into directory
  }while( dirHandle!=NULL); // If it can be casted into a TDirectory we didn't yet find what we were looking for.

  return dynamic_cast<TTree*> (objectHandle);
}