Get a Whiff of This
日本語あらすじと解説
https://speakerdeck.com/skmetz/get-a-whiff-of-this
http://confreaks.tv/videos/railsconf2016-get-a-whiff-of-this
Get a Whiff of This
これ…
ちょっと嗅いでみ？
| Long Method | Large Class | Comments |
| Message Chains | Data Clumps | Lazy Class |
| Temporary Field | Refused Bequest | Data Class |
| Divergent Change | Switch Statements | Middle Man |
| Duplicate Code | Speculative Generality | Feature Envy |
| Shotgun Surgery | |
| Inappropriate Intimacy | Long Parameter List |
| Primitive Obsession | Incomplete Library Client |
| Parallel Inheritance Hierarchies | Alternative Classes with Different Interfaces |
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
Bloaters
Tool Abusers
Change Preventers
Dispensables
Couplers
Bloaters
Large Class
Long Method
Long Parameter List
Primitive Obsession
Data Clumps
Tool Abusers
Alternative Classes with Different Interfaces
Switch Statements
Refused Bequest
Temporary Field
Change Preventers
Parallel Inheritance Hierarchies
Divergent Change
Shotgun Surgery
Dispensables
Speculative Generality
Duplicate Code
Data class
Lazy class
Couplers
Inappropriate Intimacy
Message Chains
Feature Envy
Middle Man
臭い？
class Foo
def sales_total(params)
start_date = Date.parse(params[:starting])
end_date = Date.parse(params[:ending])
Sale.where(date: start_date..end_date).sum(:cost)
end
end
class Bar
def weekly_sales_total(params)
start_date = Date.parse(params[:starting])
end_date = start_date + 6.days
Sale.where(date: start_date..end_date).sum(:cost)
end
end
class Baz
def expense_total(params)
start_date = Date.parse(params[:starting]) rescue Date.today
end_date = Date.parse(params[:ending]) rescue start_date
Expense.where(date: start_date..end_date).sum(:cost)
end
end
Data Clump
→ Extract Class
class DateRange
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
class Foo
def sales_total(params)
range = DateRange.new(params[:starting], params[:ending]).range
Sale.where(date: range).sum(:cost)
end
end
class Bar
def weekly_sales_total(params)
range = DateRange.new(params[:starting]).week_range
Sale.where(date: range).sum(:cost)
end
end
class Baz
def expense_total(params)
range = DateRange.new(params[:starting], params[:ending]).range
Expense.where(date: range).sum(:cost)
end
end
Message Chain
→ Hide Delegate
class Sale < Persistance
def self.total(within:)
where(date: within).sum(:cost)
end
end
class Expense < Persistance
def self.total(within:)
where(date: within).sum(:cost)
end
end
class Foo
def sales_total(params)
range = DateRange.new(params[:starting], params[:ending]).range
Sale.total(within: range)
end
end
class Bar
def weekly_sales_total(params)
range = DateRange.new(params[:starting]).week_range
Sale.total(within: range)
end
end
class Baz
def expense_total(params)
range = DateRange.new(params[:starting], params[:ending]).range
Expense.total(within: range)
end
end
class Foo
def sales_total(params, model = Sale)
range = DateRange.new(params[:starting], params[:ending]).range
model.total(within: range)
end
end
class Bar
def weekly_sales_total(params, model = Sale)
range = DateRange.new(params[:starting]).week_range
model.total(within: range)
end
end
class Baz
def expense_total(params, model = Expense)
range = DateRange.new(params[:starting], params[:ending]).range
model.total(within: range)
end
end
class TotalableDouble
def self.total(within:)
47
end
end
class FooTest < MiniTest::Test
def test_sales_total
params = { starting: '2016-04-01', ending: '2016-04-07' }
assert_equal 47, Foo.new.sales_total(params, TotalableDouble)
end
end
class Sale < Persistance
def self.total(within:)
where(date: within).sum(:cost)
end
end
class Expense < Persistance
def self.total(within:)
where(date: within).sum(:cost)
end
end
Duplicate Code
→ Pull Up Method
class Totalable
def total(within:)
where(date: within).sum(:cost)
end
end
class Sale < Persistance
extend Totalable
end
class Expense < Persistance
extend Totalable
end
class Totalable
def total(within:, date_field: :date, on: :cost)
where(date_field => within).sum(on)
end
end
Speculative Generality
class Totalable
def total(within:, date_field: :date, on: :cost)
where(date_field => within).sum(on)
end
end
