Programming with Values

Outline

This lesson is divided into 5 sections:

Available here

What does ‘single responsibility’ mean in a programming context?
How does programming with an eye towards the single responsibility principle help us as programmers?
In past projects, what have you decided to test? What have you decided not to test?
Why?

Common pain point when dealing with external interfaces: we make the external data dump the only interface for sending information into the object
The action of bringing outside data in is contained within the object, so our only way to provide it is to put the data in the right place (often a file) and let the object slurp it in
Programming with files/HTTP sources/Network data drives us to program with Locations rather than values
Rather than telling you the value of something I’ll tell you it’s on the whiteboard in the other classroom. Then you have to go look it up.
What does this mean for our tests?
What would an alternative look like?
Can we preserve the simple data interface (i.e. provide data in the form of ruby objects) as well as the “slurp it up from a file” interface?
Best of both worlds: Testability and flexibility when you want to provide standard basic objects; Ease of use / “Do it all” when you need to pull in a bunch of external data
Additional win: If the importing task becomes more complex, we can easily extract it into a separate entity
The interface between our objects is simple data, rather than external infrastructure

Keep these principles in mind as you complete this short Pizza Parlor Exercise