evolutionary design - refactoring heuristics

Evolutionary Design- Refactoring Heuristics -

By Adrian Bolboacă

blog.adrianbolboaca.ro

Programmer, Trainer, Coach

Focused on organizational and technical coaching

Co-Author of the Coderetreat Book leanpub.com/coderetreat

Interested in raising the bar of software development

Experimenting with Evolutionary Design for ~6 year

How do we evolve the code?Focused on solution

● Plan, Write, Deploy (waterfall)● Planned & Iterative (misunderstood Agile)● Planned & Iterative & Incorporate feedback (Scrum)

Focused on problem

● Unplanned & Iterative (misunderstood extreme programming)● Unplanned & Iterative & Incorporate feedback

(evolutionary)

CodeEvolution

FocusedOn

solution

Code Evolution: Focused on solution1. Analyze2. Find at least three solutions3. Choose the best solution4. Implement the chosen solution

a. Implement a featureb. Improve featurec. Implement next featured. Refactore. ….

5. Measure solution efficiency6. Improve the implementation7. Done

CodeEvolution

FocusedOn

problem

Code Evolution: focused on problem1. Analyze2. Understand the problem3. Find the simplest solution possible4. Implement the simplest solution possible (start with a

test)5. Complicate solution to be closer to reality (add more

tests)6. When duplication occurs, extract design elements7. When solution is good enough, stop8. Check, Test and Deploy

Refactoring● Essential in evolutionary design

“Refactoring means changing the structure of the code without changing its external observable behavior”

● Purpose: generate design specific for the problem● How: Navigate through possible solutions● Prerequisites:

○ Know design concepts and “laws”○ Observe violations of design concepts○ A lot of practice

Refactorings● Are specific● Have clear steps● Some of them are automated by tools● When used in correct order they generate flow● Often not used in correct order

Problem: When do I know how to use a specific refactoring technique?

Solution: Refactoring Heuristics

RefactoringHeuristics

Refactoring heuristics● Signs telling you when to use a refactoring● Are educated by practice● Useful not to get stuck in refactoring● Useful understanding when you used the wrong refactoring● Help you avoid mistakes● Can get you in a refactoring flow

1. Refactoring mantra1. Write / Execute simplest test2. (Write the simplest production code to make the test

pass)3. Refactor

a. Are names good enough? (variables, methods, classes, etc)b. Is the structure right (coupling, cohesion, responsibilities, etc)c. Am I going on a good path?

4. Commit to local source control5. Go to 1

After ~25 minutes take a break

Maybe push to central source control repository

2. The rule of three“Whenever I see a design element repeat itself at least three times, it might be a sign of duplication”

Solution:

1. Make duplication identical2. Use extract refactoring (constant, variable, method,

class)3. Restructure code to look nice

Hint: Always create duplication in order to remove it

3. Unnatural third party“When code throughout the system is not respecting its natural level of abstraction and will cross one or more architectural boundaries (e.g. layers) of the system”

Solution:

1. Extract the code blocks to methods 2. Move the extracted methods to a new module raising the

abstraction of the system and encapsulating the 3rd party3. Check if the code structure is correct4. If I have a vampire structure, remove it

4. Keep Small visual distance“Whenever refactoring, keep the similar pieces of code close one to another in order to spot duplication”

Solution:

● Use your IDE to move the similar methods

OR

● Copy / paste the method, then delete the initial method

5. Small code width“When the code line is too wide it is difficult to understand”

● Change the font size in your IDE to 18. If you cannot see all the code in the screen, the code is too wide.

Solutions:

● Extract method● Consolidate conditional● Consolidate logical expression

6. Adult parameter“Many methods have the same parameter in the same class”

● Typically happens when we extract pure functions from a bigger code base

Solution:

1. Create a class field for that parameter2. Change signature of each method to remove that parameter3. Check, Test & Commit

More Refactoring Heuristics● Vampire Class● Extract only Domain Concepts● Close the Closure● Zombie Class● Redundant Comment● Always rename one entity at a time● … and many more

Soon read more about them on blog.adrianbolboaca.ro

Refactoring, TDD & Structural Brain Changes

Maguire et al. 2000“The role of the hippocampus is to facilitate spatial memory, in the form of navigation”

“A correlation was found between the amount of time spent as a taxi driver and volume in the right posterior hippocampus”

“The results provide evidence [..] that extensive practice with spatial navigation affects the hippocampus”

https://www.tutor2u.net/psychology/reference/maguire-2000

So i leave you with one idea

Wire your brain by practicing refactoring if you want to be able to navigate to the best solutions. Start with Refactoring Heuristics.

Let’s Pair

I am available for face 2 face or remote pairing

Just drop a line http://blog.adrianbolboaca.ro/contact

Questions?