Class Configuration
has 25 methods (exceeds 20 allowed). Consider refactoring. Open
class Configuration
include Enumerable
HARDWIRED_DEFAULTS = {
Configuration#self.preprocess is controlled by argument 'values' Open
(values || {}).transform_values { |value| parse(value) }.with_indifferent_access
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Control Parameter
is a special case of Control Couple
Example
A simple example would be the "quoted" parameter in the following method:
def write(quoted)
if quoted
write_quoted @value
else
write_unquoted @value
end
end
Fixing those problems is out of the scope of this document but an easy solution could be to remove the "write" method alltogether and to move the calls to "writequoted" / "writeunquoted" in the initial caller of "write".
Configuration#set! refers to 'settings' more than self (maybe move it to another class?) Open
settings.allow_multiple_applications! if settings.can_allow_multiple_applications?
settings.show_multiple_applications!
else
settings.deny_multiple_applications! if settings.can_deny_multiple_applications?
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Feature Envy occurs when a code fragment references another object more often than it references itself, or when several clients do the same series of manipulations on a particular type of object.
Feature Envy reduces the code's ability to communicate intent: code that "belongs" on one class but which is located in another can be hard to find, and may upset the "System of Names" in the host class.
Feature Envy also affects the design's flexibility: A code fragment that is in the wrong class creates couplings that may not be natural within the application's domain, and creates a loss of cohesion in the unwilling host class.
Feature Envy often arises because it must manipulate other objects (usually its arguments) to get them into a useful form, and one force preventing them (the arguments) doing this themselves is that the common knowledge lives outside the arguments, or the arguments are of too basic a type to justify extending that type. Therefore there must be something which 'knows' about the contents or purposes of the arguments. That thing would have to be more than just a basic type, because the basic types are either containers which don't know about their contents, or they are single objects which can't capture their relationship with their fellows of the same type. So, this thing with the extra knowledge should be reified into a class, and the utility method will most likely belong there.
Example
Running Reek on:
class Warehouse
def sale_price(item)
(item.price - item.rebate) * @vat
end
end
would report:
Warehouse#total_price refers to item more than self (FeatureEnvy)
since this:
(item.price - item.rebate)
belongs to the Item class, not the Warehouse.
Configuration has at least 16 methods Open
class Configuration
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Too Many Methods
is a special case of LargeClass
.
Example
Given this configuration
TooManyMethods:
max_methods: 3
and this code:
class TooManyMethods
def one; end
def two; end
def three; end
def four; end
end
Reek would emit the following warning:
test.rb -- 1 warning:
[1]:TooManyMethods has at least 4 methods (TooManyMethods)
Method set!
has a Cognitive Complexity of 8 (exceeds 5 allowed). Consider refactoring. Open
def set!(name, value)
# DEPRECATED: added on 24th of February 2012
# TODO: replace all calls to .config.set!(:multiple_applications, xx)
# and remove this workaround
if name.to_sym == :multiple_applications
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Cognitive Complexity
Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.
A method's cognitive complexity is based on a few simple rules:
- Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
- Code is considered more complex for each "break in the linear flow of the code"
- Code is considered more complex when "flow breaking structures are nested"
Further reading
Configuration#delete calls 'self.class.defaults' 2 times Open
values[name] = self.class.defaults[name] if self.class.defaults.has_key?(name)
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Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.
Reek implements a check for Duplicate Method Call.
Example
Here's a very much simplified and contrived example. The following method will report a warning:
def double_thing()
@other.thing + @other.thing
end
One quick approach to silence Reek would be to refactor the code thus:
def double_thing()
thing = @other.thing
thing + thing
end
A slightly different approach would be to replace all calls of double_thing
by calls to @other.double_thing
:
class Other
def double_thing()
thing + thing
end
end
The approach you take will depend on balancing other factors in your code.
Configuration#delete calls 'self.class' 2 times Open
values[name] = self.class.defaults[name] if self.class.defaults.has_key?(name)
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Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.
Reek implements a check for Duplicate Method Call.
Example
Here's a very much simplified and contrived example. The following method will report a warning:
def double_thing()
@other.thing + @other.thing
end
One quick approach to silence Reek would be to refactor the code thus:
def double_thing()
thing = @other.thing
thing + thing
end
A slightly different approach would be to replace all calls of double_thing
by calls to @other.double_thing
:
class Other
def double_thing()
thing + thing
end
end
The approach you take will depend on balancing other factors in your code.
Configuration declares the class variable '@@defaults' Open
@@defaults ||= load_defaults
end
def self.reload
@@current = nil
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Class variables form part of the global runtime state, and as such make it easy for one part of the system to accidentally or inadvertently depend on another part of the system. So the system becomes more prone to problems where changing something over here breaks something over there. In particular, class variables can make it hard to set up tests (because the context of the test includes all global state).
For a detailed explanation, check out this article
Example
Given
class Dummy
@@class_variable = :whatever
end
Reek would emit the following warning:
reek test.rb
test.rb -- 1 warning:
[2]:Dummy declares the class variable @@class_variable (ClassVariable)
Getting rid of the smell
You can use class-instance variable to mitigate the problem (as also suggested in the linked article above):
class Dummy
@class_variable = :whatever
end
Configuration declares the class variable '@@allowed_values' Open
@@allowed_values = nil
end
# TODO: test this
def self.allowed_values
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Class variables form part of the global runtime state, and as such make it easy for one part of the system to accidentally or inadvertently depend on another part of the system. So the system becomes more prone to problems where changing something over here breaks something over there. In particular, class variables can make it hard to set up tests (because the context of the test includes all global state).
For a detailed explanation, check out this article
Example
Given
class Dummy
@@class_variable = :whatever
end
Reek would emit the following warning:
reek test.rb
test.rb -- 1 warning:
[2]:Dummy declares the class variable @@class_variable (ClassVariable)
Getting rid of the smell
You can use class-instance variable to mitigate the problem (as also suggested in the linked article above):
class Dummy
@class_variable = :whatever
end
Configuration declares the class variable '@@current' Open
@@current = nil
@@defaults = nil
@@allowed_values = nil
end
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Class variables form part of the global runtime state, and as such make it easy for one part of the system to accidentally or inadvertently depend on another part of the system. So the system becomes more prone to problems where changing something over here breaks something over there. In particular, class variables can make it hard to set up tests (because the context of the test includes all global state).
For a detailed explanation, check out this article
Example
Given
class Dummy
@@class_variable = :whatever
end
Reek would emit the following warning:
reek test.rb
test.rb -- 1 warning:
[2]:Dummy declares the class variable @@class_variable (ClassVariable)
Getting rid of the smell
You can use class-instance variable to mitigate the problem (as also suggested in the linked article above):
class Dummy
@class_variable = :whatever
end
Configuration#save! manually dispatches method call Open
@configurable.configuration_changed if @configurable.respond_to?(:configuration_changed)
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Reek reports a Manual Dispatch smell if it finds source code that manually checks whether an object responds to a method before that method is called. Manual dispatch is a type of Simulated Polymorphism which leads to code that is harder to reason about, debug, and refactor.
Example
class MyManualDispatcher
attr_reader :foo
def initialize(foo)
@foo = foo
end
def call
foo.bar if foo.respond_to?(:bar)
end
end
Reek would emit the following warning:
test.rb -- 1 warning:
[9]: MyManualDispatcher manually dispatches method call (ManualDispatch)
Configuration assumes too much for instance variable '@values' Open
class Configuration
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Classes should not assume that instance variables are set or present outside of the current class definition.
Good:
class Foo
def initialize
@bar = :foo
end
def foo?
@bar == :foo
end
end
Good as well:
class Foo
def foo?
bar == :foo
end
def bar
@bar ||= :foo
end
end
Bad:
class Foo
def go_foo!
@bar = :foo
end
def foo?
@bar == :foo
end
end
Example
Running Reek on:
class Dummy
def test
@ivar
end
end
would report:
[1]:InstanceVariableAssumption: Dummy assumes too much for instance variable @ivar
Note that this example would trigger this smell warning as well:
class Parent
def initialize(omg)
@omg = omg
end
end
class Child < Parent
def foo
@omg
end
end
The way to address the smell warning is that you should create an attr_reader
to use @omg
in the subclass and not access @omg
directly like this:
class Parent
attr_reader :omg
def initialize(omg)
@omg = omg
end
end
class Child < Parent
def foo
omg
end
end
Directly accessing instance variables is considered a smell because it breaks encapsulation and makes it harder to reason about code.
If you don't want to expose those methods as public API just make them private like this:
class Parent
def initialize(omg)
@omg = omg
end
private
attr_reader :omg
end
class Child < Parent
def foo
omg
end
end
Current Support in Reek
An instance variable must:
- be set in the constructor
- or be accessed through a method with lazy initialization / memoization.
If not, Instance Variable Assumption will be reported.
Configuration#self.parse manually dispatches method call Open
if value.respond_to?(:downcase)
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Reek reports a Manual Dispatch smell if it finds source code that manually checks whether an object responds to a method before that method is called. Manual dispatch is a type of Simulated Polymorphism which leads to code that is harder to reason about, debug, and refactor.
Example
class MyManualDispatcher
attr_reader :foo
def initialize(foo)
@foo = foo
end
def call
foo.bar if foo.respond_to?(:bar)
end
end
Reek would emit the following warning:
test.rb -- 1 warning:
[9]: MyManualDispatcher manually dispatches method call (ManualDispatch)
Configuration has missing safe method 'save!' Open
def save!
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A candidate method for the Missing Safe Method
smell are methods whose names end with an exclamation mark.
An exclamation mark in method names means (the explanation below is taken from here ):
The ! in method names that end with ! means, “This method is dangerous”—or, more precisely, this method is the “dangerous” version of an otherwise equivalent method, with the same name minus the !. “Danger” is relative; the ! doesn’t mean anything at all unless the method name it’s in corresponds to a similar but bang-less method name. So, for example, gsub! is the dangerous version of gsub. exit! is the dangerous version of exit. flatten! is the dangerous version of flatten. And so forth.
Such a method is called Missing Safe Method
if and only if her non-bang version does not exist and this method is reported as a smell.
Example
Given
class C
def foo; end
def foo!; end
def bar!; end
end
Reek would report bar!
as Missing Safe Method
smell but not foo!
.
Reek reports this smell only in a class context, not in a module context in order to allow perfectly legit code like this:
class Parent
def foo; end
end
module Dangerous
def foo!; end
end
class Son < Parent
include Dangerous
end
class Daughter < Parent
end
In this example, Reek would not report the Missing Safe Method
smell for the method foo
of the Dangerous
module.
Configuration has missing safe method 'set!' Open
def set!(name, value)
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A candidate method for the Missing Safe Method
smell are methods whose names end with an exclamation mark.
An exclamation mark in method names means (the explanation below is taken from here ):
The ! in method names that end with ! means, “This method is dangerous”—or, more precisely, this method is the “dangerous” version of an otherwise equivalent method, with the same name minus the !. “Danger” is relative; the ! doesn’t mean anything at all unless the method name it’s in corresponds to a similar but bang-less method name. So, for example, gsub! is the dangerous version of gsub. exit! is the dangerous version of exit. flatten! is the dangerous version of flatten. And so forth.
Such a method is called Missing Safe Method
if and only if her non-bang version does not exist and this method is reported as a smell.
Example
Given
class C
def foo; end
def foo!; end
def bar!; end
end
Reek would report bar!
as Missing Safe Method
smell but not foo!
.
Reek reports this smell only in a class context, not in a module context in order to allow perfectly legit code like this:
class Parent
def foo; end
end
module Dangerous
def foo!; end
end
class Son < Parent
include Dangerous
end
class Daughter < Parent
end
In this example, Reek would not report the Missing Safe Method
smell for the method foo
of the Dangerous
module.
Configuration#loaded? performs a nil-check Open
!@values.nil?
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A NilCheck
is a type check. Failures of NilCheck
violate the "tell, don't ask" principle.
Additionally, type checks often mask bigger problems in your source code like not using OOP and / or polymorphism when you should.
Example
Given
class Klass
def nil_checker(argument)
if argument.nil?
puts "argument isn't nil!"
end
end
end
Reek would emit the following warning:
test.rb -- 1 warning:
[3]:Klass#nil_checker performs a nil-check. (NilCheck)