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The C++ Spotters Guide

• Class* ObjectPtr e.g. MomNavigator* mom
  ObjectPtr is a pointer to another object. Asterisk is the dereference operator.

• Class& Object e.g. JobCROOT& jc
  Object is a reference to another object, that is to say its just an alternative name, rather like an EQUIVALENCE in fortran. Ampersand is the address and reference operator.

• dynamic_cast<Type>(Expression) e.g. dynamic_cast<RawRecord*>(mom->GetFragment("RawRecord"))
  Take the Expression and convert its type to Type. One of the most common uses is to "cast up the inheritance tree" from a base class to a subclass

• Object.MemberFunction(...) e.g. psal.GetBestSEId()
  Select i.e. call, MemberFunction of Object using the member selection operator .

• ObjectPtr->MemberFunction(...) e.g. rddb->At(idigit)
  Select i.e. call, MemberFunction of pointer ObjectPtr using the member selection operator ->

• new ClassConstructor(...) e.g. new TCanvas("my_canvas","Demo",150,10,990,660)
  Create a new TCanvas object on the heap using the new operator
  In C++ don't use malloc/free.

• delete ObjectPointer e.g. delete fRawDigits
  delete the heap object pointed to by ObjectPointer using the delete operator
  In C++ don't use malloc/free.

• Class::MemberFunction(...) e.g. JobCROOT::Instance()
  Use the scope operator to indentify a member function (or data member) of a class. With the class statement there is an implicit Class:: as part of the definition of every member. For example, in the slide above the member function Move of the class Box is declared as Move inside the class statement but defined as Box::Move outside.

• static MemberFunction(...) e.g. static JobCROOT& Instance()
  When used inside a class statement, the word static means that the function, or data member is associated with the class but not with a particular object. So, as long as not protected against outside access by the use of private or protected keywords they can be used without first accessing any object, although any reference has to be qualified by the class name using the scope operator e.g.:- JobCROOT& jc = JobCROOT::Instance();

Contact: Nick West <n.west1@physics.ox.ac.uk>

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