refactoring - agile tech conference 2016

UnderstandingRefactoring

Bryan Beecham@BillyGarnet [email protected]

Writing Healthy Code

mailto:[email protected]?subject=

@BillyGarnet

Is software designed to be simple and elegant more valuable than software that is complex and hard to maintain?

@BillyGarnet

~9600 line vb class named frm2

Continuous Improvement

Simplicity

@BillyGarnet

“Simplicity is the only thing that really scales.” –Joshua Kerievsky

@BillyGarnet

Modern AgileMake People AwesomeMake Safety a Prerequisite Experiment and Learn Rapidly Deliver Value Continuously

@BillyGarnet

RefactoringImproving the design of existing code

@BillyGarnet

“Refactoring is the process of changing a software systemin such a way that it does not alter the external behaviour

of the code yet improves its internal structure.”

–Martin Fowler

@BillyGarnet

It must work.It must be understandable.

It must be updatable.

Needs of Software

What should software do?

Reasons to extract a function

✤ To reuse it (the only reason some consider).

✤ To name it’s operation.

✤ To make it testable.

✤ To get it out of your way so you can see the code that called it more clearly.

@BillyGarnet

Remove the Clutter.Remove the Complexity.Remove the Cleverness.

Three Cs

@BillyGarnet

DuplicationDuplicationDuplication

Three Ds

@BillyGarnet

Ring of FireJohnny Cash

@BillyGarnet

➤ Love is a burnin' thing,

➤ And it makes a fiery ring

➤ Bound by wild desire

➤ I fell into a ring of fire.

➤ I fell into a burnin' ring of fire

➤ I went down, down, down

➤ And the flames went higher,

➤ And it burns, burns, burns,

➤ The ring of fire, the ring of fire.






➤ The taste of love is sweet

➤ When hearts like ours meet.

➤ I fell for you like a child

➤ Oh, but the fire went wild.







➤ I went down, down, down,






➤ The ring of fire, the ring of fire

➤ The ring of fire

@BillyGarnet

Love is a burnin' thing,

And it makes a fiery ring

Bound by wild desire

I fell into a ring of fire.

I fell into a burnin' ring of fire

I went down, down, down

And the flames went higher,

And it burns, burns, burns,

The ring of fire, the ring of fire.






The taste of love is sweet

When hearts like ours meet.

I fell for you like a child

Oh, but the fire went wild.







I went down, down, down,






The ring of fire, the ring of fire

The ring of fire

@BillyGarnet





(CHORUS)





















I went down, down, down,







The ring of fire

@BillyGarnet





(CHORUS)






CHORUS





CHORUS

CHORUS




The ring of fire

@BillyGarnet

(CHORUS)













The ring of fire





CHORUS

CHORUS

@BillyGarnet

Wow!That’s much easier to read

@BillyGarnet

Why Refactor?

Development slows over time

@BillyGarnet

Return on Investment (ROI)

@BillyGarnet

How many people have been on a project where the requirements didn’t change?

@BillyGarnet

QuotesFrom some people I like…

@BillyGarnet

“It seems that perfection is attained not when there is nothing more to add,

but when there is nothing more to remove.” –Antoine de Saint Exupéry

@BillyGarnet

“Refactoring ought to be invisible. It should be part of every task, and not a task on its own.”

~Tim Ottinger

@BillyGarnet

“It (refactoring) is the cheapest and safest way to read code. It is also the only way to safely change untestable code so that you can then start wrapping it in tests.”

~Arlo Belshee

@BillyGarnet

“ Getting an app to work is the app-titude test for a programmer.There is a lot more to programming than just getting your app to work”

~James Grenning

@BillyGarnet

“Refactoring can be done in smaller steps than you think it can, never breaking the program.”

~Ron Jeffries

@BillyGarnet

“Relentless refactoring is the single best thing you can do to fix and avoid technical debt”

~Declan Whelan

@BillyGarnet

“I refactor for one reason: to reduce volatility in the marginal cost of features.”

~J.B. Rainsberger

@BillyGarnet

“Refactoring is like breathing. You should do it all of the time without giving it much thought.”

~Jeff ‘Cheezy’ Morgan

@BillyGarnet

“We refactor to embrace change.” ~Bryan Beecham

@BillyGarnet

“You have two options, you can refactor, or you can build a big ball of mud.” ~Chet Hendrickson

@BillyGarnet

“For each desired change, make the change easy (warning: this may be hard), then make the easy change.”

~Kent Beck

@BillyGarnet

“If you’re a little better each day, next year you’ll be great. If you’re a little worse each day, next year you’ll be horrible.”

~Llewellyn Falco

@BillyGarnet

“Imagine how good a bowler you could be if you could adjust the direction of the ball once it's left your hands. Refactoring is what does that for us in writing code.”

~Woody Zuill

@BillyGarnet

“Business is well served by continuous refactoring, yet the practice of refactoring must co-exist harmoniously with business priorities.”

~Joshua Kerievsky

@BillyGarnet

“Refactoring, above all else, is a tool for managing risk.”~Amitai Schlair

@BillyGarnet

“To me, refactoring is the most pleasant part of programming. I find it meditative and soothing, to change my code and my design

until it can be grasped almost instantly.” ~Mike ‘GeePaw’ Hill

@BillyGarnet

“Rename class is the most powerful refactoring.”

~Michael Feathers

@BillyGarnet

“The way to arrest entropy in software is to refactor it.” ~Joseph Yoder

@BillyGarnet

“So if you want to go fast, if you want to get done quickly, if you want your code to be easy to write, make it easy to read.”

~Uncle Bob Martin

@BillyGarnet

HumanRefactoringGet up! Get on up!

Inside Refactoring

@BillyGarnet

Inside Refactoring

Prepare

Improve

Clean

Prepare

✤ Prepare has also been referred to as nesting, making room, prefactoring or rough-in. We make small changes to the code so the improvement can take place.

Improve

✤ Improve is when we make an improvement to the code without changing its external behaviour.

Clean

✤ Clean is when we remove code we have made unnecessary and put the code back in a state to start something new.

✤ At this point we are done refactoring and can run tests, and, assuming they pass, integrate this refactoring.

Make a sandwich

✤ Get out all the things you need

✤ Assemble the sandwich

✤ Put everything away

Working Effectively with Legacy Code

✤ 1. Identify the code you want to extract and comment it out.

✤ 2. Think of a new name for a method and create it as an empty method.

✤ 3. Place a call to the new method in the old method.

✤ 4. Copy the code you want to extract into the new method.

✤ 5. Lean on the Compiler to find out what parameters you’ll have to pass and what values you’ll have to return.

✤ 6. Adjust the method declaration to accommodate the parameters and return value (if any).

✤ 7. Run your tests.

✤ 8. Delete your commented out code.

Prepare

✤ 1. Identify the code you want to extract and comment it out.

✤ 2. Think of a new name for a method and create it as an empty method.

✤ 3. Place a call to the new method in the old method.

Improve

✤ 4. Copy the code you want to extract into the new method.

✤ 5. Lean on the Compiler to find out what parameters you’ll have to pass and what values you’ll have to return.

✤ 6. Adjust the method declaration to accommodate the parameters and return value (if any).

✤ 7. Run your tests.

Clean

✤ 8. Delete your commented out code.

@BillyGarnet

Inside RefactoringExample

@BillyGarnet

@BillyGarnet

Inside Refactoring

Prepare

Improve

Clean

@BillyGarnet

def convert(arabic): numeral = "" for i in range(0, arabic): numeral += "I" return numeral

@BillyGarnet

def convert(arabic): numeral = "" current_number = arabic

for i in range(0, current_number): if current_number >= 10: numeral += "X" current_number -= 10

for i in range(0, current_number): numeral += "I"

return numeral

@BillyGarnet

def convert(arabic): numeral = ""

for i in range(0, arabic): if arabic >= 10: numeral += "X" arabic -= 10

for i in range(0, arabic): if arabic >= 1: numeral += "I" arabic -= 1

return numeral

@BillyGarnet


arabic_value = 10 roman_value = "X" for i in range(0, arabic): if arabic >= arabic_value: numeral += roman_value arabic -= arabic_value

arabic_value = 1 roman_value = "I" for i in range(0, arabic): if arabic >= arabic_value: numeral += roman_value arabic -= arabic_value

return numeral

@BillyGarnet


arabic_digits = [10, 1] roman_digits = ["X", "I"] for i in range(0, len(arabic_digits)): while arabic >= arabic_digits[i]: numeral += roman_digits[i] arabic -= arabic_digits[i]

# arabic_digits = 1 # roman_digits = "I" # for i in range(0, arabic): # if arabic >= arabic_digits: # numeral += roman_digits # arabic -= arabic_digits

return numeral

@BillyGarnet


arabic_digits = [10, 1] roman_digits = ["X", "I"] for i in range(0, len(arabic_digits)): while arabic >= arabic_digits[i]: numeral += roman_digits[i] arabic -= arabic_digits[i]

return numeral

@BillyGarnet

arabic_digits = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1] roman_digits = ['M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I']

@BillyGarnet

Inside Refactoring

Prepare

Improve

Clean

Bryan Beecham@BillyGarnet [email protected]

Questions and Answers

mailto:[email protected]?subject=

Questionable Code

Clarity

if (x){ return true } else if (!x) { return false }

if (x) return true return false

if (x){ return true

} else if (!x) { return false

}

return x

Clutter

;

Clutter

// // This is cool// I saw it on a blog and thought if we changed our code// it could work. Call me if you need more explanation////

@BillyGarnet

Books

✤ Refactoring - Martin Fowler

✤ Working Effectively with Legacy Code - Michael Feathers

✤ Refactoring to Patterns - Joshua Kerievsky

✤ Refactoring Workbook - Bill Wake

✤ Healthy Code - Getting Started with Refactoring - Bryan Beecham