Style Guide

The following guidelines are common to most software development projects:
  • use design patterns,
  • always protect attributes,
  • avoid multiple inheritance

Design patterns

Design patterns are general repeatable solutions to problems commonly encountered in software design. It is very infrequent that a specific software design question has not already been answered, and it saves a lot of time and effort to be familiar with this body of work.

Protect Attributes

No matter how simple your class, all of its attributes (member variables) should be protected or private and access should be mediated through separate set and get methods (member functions). This is not merely a matter of style; the primary benefit of this component of data abstraction is design flexibility:
  • one may later decide that an attribute is either redundant or needs generalization; a good example is the reference_frequency attribute of the Calibration::Faraday class. When it was required to correct to infinite frequency, it became better to store the reference as a wavelength. The change to the internal storage of the attribute required no changes to any code that used the get|set_reference_frequency methods.
  • any additional error checking and/or other behaviours may be implemented in set and/or get methods; for example, a base class may ensure that preprocessing steps are performed on input data by making the input data attribute private and implementing these steps in the set input data method;
  • set and get methods enable lazy evaluation; e.g.
      //  the result attribute is cached internally and recomputed only when necessary 
      void MyClass::set_attribute (double new_value)
        if (current_value == new_value)
        needs_computation = true;
        current_value = new_value;
      double MyClass::get_result () const
        if (needs_computation)
          compute_result ();
        return result;

Avoid Multiple inheritance

Multiple inheritance should be used judiciously; an excellent alternative is the Policy or Strategy behavioural design pattern.