obliviusm/ruby_refactoring_patterns.md

## ruby_refactoring_patterns.md

      
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    Object-Oriented Design and Refactoring Patterns in Ruby


source: https://code.tutsplus.com/courses/object-oriented-design-and-refactoring-patterns-in-ruby
all refactoring patterns: http://refactoring.com/catalog/
video lessons

Code Smells

Each item in the following list matches a code smell and contains a list of
possible refactoring patterns to solve it.


Duplicate code

Extract Method
Pull Up Method
Form Template Method


Long method

Extract Method
Replace Temp with Query / Replace Temp with Chain
Introduce Parameter Object / Preserve Whole Object
Replace Method with Method Object


Feature envy - «функциональная зависть», функціональна залежність

Extract Method + Move Method


Data clumps

Extract Class
Introduce Parameter Object / Preserve Whole Object


Comments

Rename Method
Extract Method
Introduce Assertion


Divergent change

Extract Class
Inline Class
Move Method + Move Field


Primitive Obsession

Replace Type Code with Polymorphism / Module Extension / State|Strategy
Replace Array with Object
Introduce Parameter Object


Conditionals (if/else, case/when)

Introduce Null Object
Replace Type Code with Polymorphism
Extract Method + Move Method


Refactoring Patterns


Extract Class

problem: You have one class doing work that should be done by two.
solution: Create a new class and move the relevant fields and methods from the old class into the new class.
example: http://refactoring.com/catalog/extractClass.html


Extract Method

problem: You have a code fragment that can be grouped together.
solution: Turn the fragment into a method whose name explains the purpose of the method.
example: http://refactoring.com/catalog/extractMethod.html


Form Template Method

problem: You have two methods in subclasses that perform similar steps in the same order, yet the steps are different.
solution: Get the steps into methods with the same signature, so that the original methods become the same. Then you can pull them up.
example: http://refactoring.com/catalog/formTemplateMethod.html


Hide Delegate

problem: A client is calling a delegate class of an object.
solution: Create methods on the server to hide the delegate.
example: http://refactoring.com/catalog/hideDelegate.html


Introduce Assertion

problem: A section of code assumes something about the state of the program.
solution: Make the assumption explicit with an assertion.
example: http://refactoring.com/catalog/introduceAssertion.html


Introduce Null Object

problem: You have repeated checks for a null value.
solution: Replace the null value with a null object.
example: http://refactoring.com/catalog/introduceNullObject.html


Separate Query from Modifier

problem: You have a method that returns a value but also changes the state of an object.
solution: Create two methods, one for the query and one for the modification.
example: http://refactoring.com/catalog/separateQueryFromModifier.html


Move Field

problem: A field is, or will be, used by another class more than the class on which it is defined.
solution: Create a new field in the target class, and change all its users.
example: http://refactoring.com/catalog/moveField.html


Parameterize Method

problem: Several methods do similar things but with different values contained in the method body.
solution: Create one method that uses a parameter for the different values.
example: http://refactoring.com/catalog/parameterizeMethod.html


Preserve Whole Object

problem: You are getting several values from an object and passing these values as parameters in a method call.
solution: Send the whole object instead.
example: http://refactoring.com/catalog/preserveWholeObject.html


Pull Up Method

problem: Two subclasses have the same field.
solution: Move the field to the superclass.
example: http://refactoring.com/catalog/pullUpField.html


Rename Method

problem: The name of a method does not reveal its purpose.
solution: Change the name of the method.
example: http://refactoring.com/catalog/renameMethod.html


Replace Array with Object

problem: You have an array in which certain elements mean different things.
solution: Replace the array with an object that has a field for each element.
example: http://refactoring.com/catalog/replaceArrayWithObject.html


Replace Method with Method Object


Replace Temp with Query


Replace Type Code with Module Extension


Replace Type Code with Polymorphism


Replace Type Code with State/Strategy