Refactoring
Primitive Obsession
jamesdabbs
[Live]
Kent Beck
Martin Fowler
@martinfowler
@KentBeck
Sandi Metz
Katrina Owen
@kytrinyx
@sandimetz
Refactoring
a change made to the internal structure of software
to make it easier to understand and cheaper to modify
without changing its observable behavior.
— Martin Fowler, Refactoring
ri-fak-tər-iŋ
(n)
How‽
But
If it ain't broke,
don't fix it.
Is it open for the new requirement?
Is it really open for the new requirement?
😎
Is it really open for the new requirement?
Do you know how to make it open?
😎
Is it really open for the new requirement?
Pick the code smell closest to the requirement
Apply a curative recipe for that code smell
😎
Primitive Obsession
using primitive types to represent business objects
Primitive Obsession
Primitive Obsession
Recipes
Replace Primitive with Object
- Create a simple value class with a getter
- Run static checks
- Change the setting code to create an instance of the value class
- Run tests
- Consider applying "change reference to value" or "change value to reference"
Replace Conditional with Polymorphism
- Create classes for polymorphic behavior
- Create a factory function to return the correct instance
- Use the factory function in calling code
- Move the conditional to the parent class
- Override each successive leg of the conditional
- Replace the parent class conditional
Good luck!
Takeaways
Now Easy
- getting starting without knowing the end state
- stopping and shipping before reaching the end state
Important, Still Hard
- running tests quickly
- trusting your coverage
- working with QAs
- refactoring Rails magic methods
- finding all callers of a method
Running Tests Quickly
- set up guard and spring
- small objects
- decoupled from ActiveRecord
Trusting Your Coverage
- test more
- consider in-production tests
- science experiments
Trusting Your Coverage
Working with QAs
- talk about regression tests
- talk about development practices
Refactoring Rails Magic
- decouple where you can
- use magic when it makes sense
Finding All Callers
- use descriptive names
- don't get fancy with dynamic send
- consider deprecating, not deleting
"We can't take the time to refactor,
we have features we have to ship."
If you don't need to change your product
don't change your code
If you need to change your code
make it easy to change
Read These
Practice
We're hiring
Write the simplest thing that you need today;
you can always change it tomorrow
Refactoring Live: Primitive Obsession
By James Dabbs
Refactoring Live: Primitive Obsession
Let's roll up our sleeves and clean up some smelly code. In this session, we'll dig in to Primitive Obsession - what happens when our domain logic is all wrapped up in primitive data types? And most importantly, how do we untangle it? Code presented in this talk is available at https://github.com/jamesdabbs/greatbook.
