Question

I’ve read all the books about why to create a class and things like ‘look for the nouns in your requirements’ but it doesn’t seem to be enough. My classes seem to me to be messy. I would like to know if there are some sort of metrics or something that I can compare my classes to and see if there well designed. If not, who is the most respected OO guru where I can get the proper class design tips?

Answer 1

if you’re familiar with database design, specifically the concept of normalization, then the answer is easy: a data-centric class should represent an entity in third normal form

if that is not helpful, try this instead:

• a class is a collection of data elements and the methods that operate on them
• a class should have a singular responsibility, i.e. it should represent one thing in your model; if it represents more than one thing then it should be more than one class.
• all of the data elements in a class should be logically associated/related to each other; if they aren’t, split it into two or more classes
• all of the methods in a class should operate only on their input parameters and the class’s data elements – see the Law of Demeter

that’s about as far as i can go with general abstract advice (without writing a long essay); you might post one of your classes for critique if you need specific advice