Tag: domain-driven design

Builder Methods ◰ 2014-04-29 1:32
Code: domain-driven design, immutability, Ruby, testing, validity
3 comments

I was reading Corey Haines’ book Understanding the Four Rules of Simple Design (capsule review on the 2014 book reviews post) when I read:

In fact, over time I’ve developed a guideline for myself that external callers can’t actually use the base constructor for an object. Put another way: the outside world can’t use new to instantiate an object with an expectation of a specific state. Instead, there must be an explicitly named builder method on the class to create an object in a specific, valid state.

This was a brief aside at the tail of a longer discussion of interdependent and redundant tests. It really caught my attention and I’d like to hear it more thoroughly investigated. In the hopes of attracting Corey’s attention, I offer this cat pic and an exploration of the benefits of a similar practice I have: