refactoring - agile tech conference 2016
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UnderstandingRefactoring
Bryan Beecham@BillyGarnet bryan@industriallogic.com
Writing Healthy Code
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Is software designed to be simple and elegant more valuable than software that is complex and hard to maintain?
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~9600 line vb class named frm2
Continuous Improvement
Simplicity
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“Simplicity is the only thing that really scales.” –Joshua Kerievsky
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Modern AgileMake People AwesomeMake Safety a Prerequisite Experiment and Learn Rapidly Deliver Value Continuously
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RefactoringImproving the design of existing code
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“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
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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.
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Remove the Clutter.Remove the Complexity.Remove the Cleverness.
Three Cs
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DuplicationDuplicationDuplication
Three Ds
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Ring of FireJohnny Cash
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➤ 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.
➤ 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 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.
➤ 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.
➤ And it burns, burns, burns,
➤ The ring of fire, the ring of fire.
➤ 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.
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 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.
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.
And it burns, burns, burns,
The ring of fire, the ring of fire.
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.
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 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.
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.
And it burns, burns, burns,
The ring of fire, the ring of fire.
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.
(CHORUS)
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.
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 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.
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.
And it burns, burns, burns,
The ring of fire, the ring of fire.
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.
(CHORUS)
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.
CHORUS
The taste of love is sweet
When hearts like ours meet.
I fell for you like a child
Oh, but the fire went wild.
CHORUS
CHORUS
And it burns, burns, burns,
The ring of fire, the ring of fire.
The ring of fire, the ring of fire
The ring of fire
@BillyGarnet
(CHORUS)
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.
And it burns, burns, burns,
The ring of fire, the ring of fire.
The ring of fire, the ring of fire
The ring of fire
Love is a burnin' thing,
And it makes a fiery ring
Bound by wild desire
I fell into a ring of fire.
CHORUS
CHORUS
@BillyGarnet
Wow!That’s much easier to read
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Why Refactor?
Development slows over time
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Return on Investment (ROI)
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How many people have been on a project where the requirements didn’t change?
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QuotesFrom some people I like…
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“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
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“Refactoring ought to be invisible. It should be part of every task, and not a task on its own.”
~Tim Ottinger
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“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
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“ 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
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“Refactoring can be done in smaller steps than you think it can, never breaking the program.”
~Ron Jeffries
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“Relentless refactoring is the single best thing you can do to fix and avoid technical debt”
~Declan Whelan
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“I refactor for one reason: to reduce volatility in the marginal cost of features.”
~J.B. Rainsberger
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“Refactoring is like breathing. You should do it all of the time without giving it much thought.”
~Jeff ‘Cheezy’ Morgan
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“We refactor to embrace change.” ~Bryan Beecham
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“You have two options, you can refactor, or you can build a big ball of mud.” ~Chet Hendrickson
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“For each desired change, make the change easy (warning: this may be hard), then make the easy change.”
~Kent Beck
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“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
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“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
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“Business is well served by continuous refactoring, yet the practice of refactoring must co-exist harmoniously with business priorities.”
~Joshua Kerievsky
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“Refactoring, above all else, is a tool for managing risk.”~Amitai Schlair
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“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
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“Rename class is the most powerful refactoring.”
~Michael Feathers
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“The way to arrest entropy in software is to refactor it.” ~Joseph Yoder
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“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
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HumanRefactoringGet up! Get on up!
Inside Refactoring
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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.
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Inside RefactoringExample
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Inside Refactoring
Prepare
Improve
Clean
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def convert(arabic): numeral = "" for i in range(0, arabic): numeral += "I" return numeral
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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
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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
def convert(arabic): numeral = ""
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
def convert(arabic): numeral = ""
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
def convert(arabic): numeral = ""
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
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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 bryan@industriallogic.com
Questions and Answers
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////
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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
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