Am 05.04.2012 22:18, schrieb Ronan Lamy:
To know
whether something should be a function or an object, you need to ask
yourself whether it's an action or a thing. Here, we clearly have
actions, because the names you use are verb phrases.
I don't know whether you or Ashwini is right about what should be an
object and what should be a class in this particular case.
However, in general, looking at what's a verb and what's a noun is
definitely not a good way to do class design. I haven't used that
particular method of class design in all my 20 years of OO programming
and design, except maybe once in my experimental phase (and quickly
discarded the results because the resulting design was easily improved
by using other criteria). Also, I found that almost any specification
can be rephrased from using verbs to using nouns and back, without
changing the requirements on the implementation; so that's not going to
be very helpful.
So what are good criteria?
- If you have a bunch of related data that is connected via consistency
conditions, putting the data into a class and making it private will
make sure that no code erroneously introduces inconsistencies.
- If you need polymorphism (i.e. the "semantically same" function needs
to do different things depending on what the type of the data is that
it's working on). There are alternatives to using a class in such a
situation, and it isn't even rare that they are better.
- ... okay, I think there are more criteria, but it's too late and I
don't have the time to cover all aspects of good OO design right now :-)
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sympy?hl=en.
