Get a Whiff of This

Transcript

May 2016
@sandimetz
Sandi Metz
Get a Whiﬀ
of This
Sandi Metz

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@sandimetz May 2016
Kent Beck

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@sandimetz May 2016
Kent Beck Martin Fowler

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@sandimetz May 2016
Kent Beck Martin Fowler

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@sandimetz May 2016
Classic Smells

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@sandimetz May 2016
Classic Smells
Alternative Classes
w/ Diﬀerent Interfaces
Comments
Data Class
Data Clumps
Divergent Change
Duplicated Code
Feature Envy
Parallel Inheritance
Hierarchies
Primitive Obsession
Refused Bequest
Shotgun Surgery
Speculative Generality
Switch Statements
Temporary Field
Inappropriate Intimacy
Incomplete Library Client
Large Class
Long Method
Long Parameter List
Message Chains
Middle Man
Lazy Class

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@sandimetz May 2016

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@sandimetz May 2016
Alternative Classes
Comments
Data Class
Data Clumps
Divergent Change
Duplicated Code
Feature Envy
Hierarchies
Primitive Obsession
Refused Bequest
Shotgun Surgery
Switch Statements
Temporary Field
Classic Smells
Large Class
Long Method
Long Parameter List
Message Chains
Middle Man
Lazy Class

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@sandimetz May 2016
Alternative Classes
Comments
Data Class
Data Clumps
Divergent Change
Duplicated Code
Feature Envy
Hierarchies
Primitive Obsession
Refused Bequest
Shotgun Surgery
Switch Statements
Temporary Field
Classic Smells
Long Method
Long Parameter List
Message Chains
Middle Man
Lazy Class
Large Class

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@sandimetz May 2016
Alternative Classes
Data Class
Data Clumps
Divergent Change
Duplicated Code
Feature Envy
Hierarchies
Primitive Obsession
Refused Bequest
Shotgun Surgery
Switch Statements
Temporary Field
Classic Smells
Long Method
Long Parameter List
Message Chains
Middle Man
Lazy Class
Large Class

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@sandimetz May 2016
Divergent Change
Hierarchies
Shotgun Surgery
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field
Feature Envy
Message Chains
Middle Man
Data Class
Duplicated Code
Lazy Class
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class

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@sandimetz May 2016
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class

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@sandimetz May 2016
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class

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@sandimetz May 2016
Bloaters
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class

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@sandimetz May 2016
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field
Divergent Change
Hierarchies
Shotgun Surgery
Feature Envy
Message Chains
Middle Man
Data Class
Duplicated Code
Lazy Class
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class
Bloaters

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@sandimetz May 2016
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field

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@sandimetz May 2016
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field

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@sandimetz May 2016
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field

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@sandimetz May 2016
Tool Abusers
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field

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@sandimetz May 2016
Divergent Change
Hierarchies
Shotgun Surgery
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field
Feature Envy
Message Chains
Middle Man
Data Class
Duplicated Code
Lazy Class
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class
Bloaters
Abusers
Divergent Change
Hierarchies
Shotgun Surgery

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Divergent Change
Hierarchies
Shotgun Surgery
Divergent Change
Hierarchies
Shotgun Surgery

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@sandimetz May 2016
Divergent Change
Hierarchies
Shotgun Surgery

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@sandimetz May 2016
Divergent Change
Hierarchies
Shotgun Surgery

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@sandimetz May 2016
Change Preventers
Divergent Change
Hierarchies
Shotgun Surgery

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@sandimetz May 2016
Data Class
Duplicated Code
Lazy Class
Feature Envy
Message Chains
Middle Man
Divergent Change
Hierarchies
Shotgun Surgery
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class
Bloaters
Abusers
Preventers

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@sandimetz May 2016
Data Class
Duplicated Code
Lazy Class

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Data Class
Duplicated Code
Lazy Class

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Data Class
Duplicated Code
Lazy Class

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Dispensables Data Class
Duplicated Code
Lazy Class

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@sandimetz May 2016
Feature Envy
Message Chains
Middle Man
Data Class
Duplicated Code
Lazy Class
Divergent Change
Hierarchies
Shotgun Surgery
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class
Bloaters
Abusers
Preventers
Dispensables

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Feature Envy
Message Chains
Middle Man

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Feature Envy
Message Chains
Middle Man

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Feature Envy
Message Chains
Middle Man

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@sandimetz May 2016
Couplers
Feature Envy
Message Chains
Middle Man

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Feature Envy
Message Chains
Middle Man
Data Class
Duplicated Code
Lazy Class
Divergent Change
Hierarchies
Shotgun Surgery
Alternative Classes
Refused Bequest
Switch Statements
Temporary Field
Data Clumps
Primitive Obsession
Long Method
Long Parameter List
Large Class
Bloaters
Abusers
Preventers
Dispensables
Couplers

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Refactoring

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Refactoring Recipe

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Fowler 149:
Extract Class

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Refactoring Recipe

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Code Smell
Curative Refactoring Recipe

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http://www.industriallogic.com/wp-content/uploads/2005/09/smellstorefactorings.pdf

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http://www.industriallogic.com/wp-content/uploads/2005/09/smellstorefactorings.pdf

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1

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class Sale < Persistence
end

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end
class Foo
def sales_total(params)
Sale.where(date: (Date.parse(params[:starting]))..(Date.parse(params[:ending]))).sum("cost")
end
end

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end
class Foo
end
end

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end
class Foo
end
end

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end
class Foo
end
end

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end
class Foo
end
end

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end
class Foo
end
end

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end
class Foo
end
end

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end
class Foo
end
end

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end
class Foo
end
end
class Bar
def weekly_sales_total(params)
start_date = (Date.parse(params[:starting]))
end_date = start_date + 6
Sale.where(date: (start_date..end_date)).sum("cost")
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Foo
end
end
class Bar
end
end

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end
class Expense < Persistence
end
class Foo
end
end
class Bar
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
def expense_total(params)
Expense.where(date: (Date.parse(params[:starting]))..(Date.parse(params[:ending]))).sum("cost")
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end
Kaboom

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
start_date = (Date.parse(params[:starting])) rescue Date.today
end_date = (Date.parse(params[:ending])) rescue start_date
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end
class Larry
end
end
class Curly
end
end
class Mo
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end
class Larry
end
end
class Curly
end
end
class Mo
end
end
class Fee
end
end
class Fi
end
end
class Foe
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end
class Larry
end
end
class Curly
end
end
class Mo
end
end
class Fee
end
end
class Fi
end
end
class Foe
end
end

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2
Data Clump | Extract Class

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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class DateRange
attr_reader :starting, :ending
def initialize(starting:, ending: nil)
@starting = Date.parse(starting) rescue Date.today
@ending = Date.parse(ending) rescue @starting
end
def range
starting..ending
end
def week_range
starting..(starting + 6)
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Foo
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Foo
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Foo
range = DateRange.new(starting: params[:starting], ending: params[:ending]).range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Foo
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Foo
Sale.where(date: range).sum("cost")
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Bar
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Bar
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Bar
range = DateRange.new(starting: params[:starting]).week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Bar
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Bar
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Baz
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Baz
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Baz
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Baz
Expense.where(date: range).sum("cost")
end
end

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class DateRange
end
def range
starting..ending
end
def week_range
end
end
class Baz
end
end

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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class Foo
end
end
class Bar
end
end
class Baz
end
end
Data Clump | Extract Class

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3
Message Chain | Hide Delegate

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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Foo

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Foo Sale

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Foo Sale
where

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Foo Sale
Persistence
where

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Foo Sale
Persistence
where
where

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Foo Sale
Persistence
where
where

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Foo Sale
Persistence
where
where
List

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Foo Sale
Persistence
where
where
List
??? ??? ???

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Foo Sale
Persistence
where
where
List
??? ??? ???

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Foo Sale
Persistence
where
where
List
??? ??? ???

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Foo Sale
Persistence
where
where
List
a list
??? ??? ???

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Foo Sale
Persistence
where
where
List
a list
a list
??? ??? ???

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Foo Sale
Persistence
where
where
List
sum
a list
a list
??? ??? ???

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Foo

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DateRange
Foo

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Sale
#where
DateRange
Foo

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Sale
#where
DateRange
Foo
Immediate Collaborators

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List
#sum
Sale
#where
DateRange
Foo

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List
#sum
Sale
#where
DateRange
Foo

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List
#sum
Sale
#where
DateRange
Foo

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List
#sum
Sale
#where
DateRange
Foo
I know my collaborators collaborators

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List
#sum
Sale
#where
DateRange
Foo
This is gonna hurt

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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class Foo
end
end
class Bar
end
end
class Baz
end
end

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def self.total(within:)
where(date: within).sum("cost")
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
class Foo
end
end
class Bar
end
end

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end
end
class Foo
end
end
class Bar
end
end

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end
end
class Foo
Sale.total(within: range)
end
end
class Bar
end
end

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end
end
class Foo
end
end
class Bar
end
end

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end
end
class Foo
end
end
class Bar
end
end

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end
end
class Foo
end
end
class Bar
end
end

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end
end
class Foo
end
end
class Bar
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
Expense.total(within: range)
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end

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end
end
end
end
class Foo
end
end
class Bar
end
end
class Baz
end
end
Message Chain | Hide Delegate

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4
Sidebar: How Much Reality?

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end
end
class Foo
end
end

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end
end
class Foo
end
end

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end
end
class Foo
end
end

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end
end
class Foo
end
end

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end
end
class Foo
end
end
# Slow Test
class FooTest < Minitest::Test
def test_sales_total
assert_equal 28, Foo.new.sales_total(starting: "2016-04-01", ending: "2016-04-07")
end
end

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end
Check the query result

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
end
end
Depend on Sale class?

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end
Depend on Totalizable role!

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
def sales_total(params, model=Sale)
end
end
# Slow Test
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
model.total(within: range)
end
end
# Slow Test
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
end
end

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end
end
class Foo
end
end
# Slow Test
class TotalizableDouble
47
end
end
end
end

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
end
end
Two players of the Totalizable role

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
params = {:starting => "2016-04-01", :ending => "2016-04-07"}
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
assert_equal 28, Foo.new.sales_total(params)
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
model = TotalizableDouble
end
end

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
assert_equal 28, Foo.new.sales_total(params, model)
end
end

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end
FAST

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end
end
class Foo
end
end
# Slow Test
47
end
end
end
end

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@sandimetz May 2016
end
end
class Foo
end
end
# FAST Test
47
end
end
end
end

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@sandimetz May 2016
5
Duplicated Code | Pull Up Method

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end
end
end
end

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@sandimetz May 2016
end
end
end
end

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@sandimetz May 2016
end
end
end
end

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@sandimetz May 2016
end
end
end
end

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@sandimetz May 2016
module Totalable
def total(within:, date_field: :date, on: "cost")
where({date_field => within}).sum(on)
end
end
end
end
end
end

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@sandimetz May 2016
module Totalable
end
end
end
end
end
end

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@sandimetz May 2016
module Totalable
end
end
end
end
end
end

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@sandimetz May 2016
module Totalable
end
end
end
end
end
end

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@sandimetz May 2016
module Totalable
end
end
end
end
end
end
Dependency Injection
Is
Awesome

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@sandimetz May 2016
module Totalable
end
end
end
end

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@sandimetz May 2016
module Totalable
end
end
extend Totalable
end
extend Totalable
end

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@sandimetz May 2016
module Totalable
end
end
extend Totalable
end
extend Totalable
end

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@sandimetz May 2016
module Totalable
end
end
extend Totalable
end
extend Totalable
end
Duplicated Code | Pull Up Method

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@sandimetz May 2016
Code Smell
Curative Refactoring Recipe

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@sandimetz May 2016

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@sandimetz May 2016
class DateRange
end
def range
starting..ending
end
def week_range
end
end

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@sandimetz May 2016
module Totalable
end
end
extend Totalable
end
extend Totalable
end

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@sandimetz May 2016
class Foo
end
end
class Bar
def weekly_sales_total(params, model=Sale)
end
end
class Baz
def expense_total(params, model=Expense)
end
end

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@sandimetz May 2016
Fist Pump

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@sandimetz May 2016
Fist Pump

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@sandimetz May 2016

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@sandimetz May 2016
Reek

@sandimetz May 2016

@sandimetz May 2016

@sandimetz May 2016

@sandimetz May 2016

@sandimetz
Thanks
May 2016

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@sandimetz
References
May 2016
http://martinfowler.com/books/refactoring.html

http://www.refactoringinruby.info/ Kevin Rutherford, William Wake

Mäntylä, M. V. and Lassenius, C. "Subjective Evaluation of Software Evolvability Using Code Smells: An
Empirical Study". Journal of Empirical Software Engineering, vol. 11, no. 3, 2006, pp. 395-431.
https://github.com/troessner/reek

https://blog.codeship.com/how-to-ﬁnd-ruby-code-smells-with-reek

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@sandimetz
Credits
May 2016
Coffee on a Winter's morning, Stefan Lins, https://www.flickr.com/photos/mrlins/8533102693/
Royal Australian Air Force in Australia during World War II, Argus Newspaper Collection of Photographs, State
Library of Victoria, https://www.flickr.com/photos/statelibraryofvictoria_collections/16554906225/
Chevy Crusher, Ruby Eng , https://www.flickr.com/photos/mac-ash/4105522760/
Misuse Makes Mishaps, Jeremy Brooks , https://www.flickr.com/photos/jeremybrooks/2205135193,
resistance is futile, Lora, https://www.flickr.com/photos/laroyo/6871150550/
Well this is pointless, Janet McKnight, https://www.flickr.com/photos/janetmck/2613441853/
Glue goo 3, Sam-Cat, https://www.flickr.com/photos/samcatchesides/3326878644/
poses of victory, Daniel Novta, https://www.flickr.com/photos/vanf/7304661962/
Odorous smells!, auddess, https://www.flickr.com/photos/auddess/4744679975
EXPLORE] Smell the Flowers, Christine und David Schmitt, https://www.flickr.com/photos/cheesy42/8624536219/
PIZZA, Tobi Gaulke. https://www.flickr.com/photos/gato-gato-gato/15958062095/
Ain't Life Grand, Anne Worner, https://www.flickr.com/photos/wefi_official/9305161946/

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