Refactorings Flashcards
Define Rename Method/Field
Description: Method/field name doesn’t explain what it does
Smell: Comments
Fix: Rename the method
Define Extract Method
Description: Too long of methods or code needs comments to be understood
Smell: duplicate code, long method, feature envy, comments, switch statements, data class, message chains, data class
Fix: Take out related code from function and create a new method with it
Define Substitute Algorithm
Description: So you want to replace an existing algorithm with a new one?
Smell: duplicate code, long method
Fix: Replace the body of the method that implements the algorithm with a new algorithm.
Define Introduce Explaining Variable
Description: You have a really complex expression
Smell: ?
Fix: Create a local/temp variable to simplify expression and define what is happening
Define Replace Temp with Query
Description: You place the result of an expression (i.e a = b*c) in a local variable for later use in your code.
Smell: Long method, duplicate code
Fix: Move the entire expression to a separate method and return the result from it. Query the method instead of using a variable. Incorporate the new method in other methods, if necessary.
Define Replace Magic Number with Symbolic Constant
Description: Repeated use of a number to represent something (i.e 9.81 as gravity)
Smell: Comments
Fix: define final static variable to help make the number understandable
Define Add/Remove Parameter
Description: A method is missing data/A parameter isn’t used in the body of a method.
Smell: Speculative Generality(remove param)
Fix: Create copy of method but with necessary parameter/remove unused parameter from method.
Define Encapsulate Field
Description: You have a public variable
Smell: Data Class
Fix: Make it private and add getters and setters
Define Extract Class
Description: When one class does the work of two, awkwardness results.
Smell: Duplicate code, large class, divergent change, data clumps, primitive obsession, temporary fields, inappropriate intimacy
Fix: Instead, create a new class and place the fields and methods responsible for the relevant functionality in it.
Define Extract Superclass
Description: You have two classes with common fields and methods.
Smell: Duplicate code
Fix: Create a shared superclass for them and move all the identical fields and methods to it.
Define Move Method/Field
Description: A method/field is used more in another class than in its own class.
** rule of thumb is to put field in the class that has the most methods using it
Smell: Data class, shotgun surgery, message chains, inappropriate intimacy, switch statements, parallel inheritance hierarchy
Fix: Create a new method in the class that uses the method the most, then move code from the old method to there. Turn the code of the original method into a reference to the new method in the other class or else remove it entirely.
Define Pull up method/field
Description: Your subclasses have methods that perform similar work or duplicate fields.
Smell: duplicate code
Fix: Make the methods/fields identical and then move them to the relevant superclass.
Define Push down method/field
Description: method/field is only used in a few subclasses
Smell: Refused Bequest
Fix: push down method/field to subclasses that actually use it
Define Replace Constructor with Factory method
Description: You have a complex constructor that does something more than just setting parameter values in object fields.
Smell: ?
Fix: Create a factory (static) method and use it to replace constructor calls.
Define Form Template Method
Description: Your subclasses implement algorithms that contain similar steps in the same order.
Smell: Duplicate Code
Fix: Move the algorithm structure and identical steps to a superclass, and leave implementation of the different steps in the subclasses.
Define Collapse Hierarchy
Description: You have a class hierarchy in which a subclass is practically the same as its superclass.
Smell: Lazy class, speculative generality
Fix: Merge sub and superclass
Define Remove Middle Man
Description: A class has too many methods that simply delegate to other objects. (i.e class1 calls class2 to call method from class3)
Smell: Middle man
Fix: Delete these methods and force the client to call the end methods directly. (delete original class1 methods and have class1 call class3 directly)
Define Hide Delegate
Description: The client gets object B from a field or method of object А. Then the client calls a method of object B.
Smell: Message Chains, Inappropriate Intimacy
Fix: Create a new method in class A that delegates the call to object B. Now the client doesn’t know about, or depend on, class B.
Define Remove Conditional with Polymorphism
Description: You have a conditional that performs various actions depending on object type or properties.
Smell: switch statements
Fix: Create subclasses matching the branches of the conditional. In them, create a shared method and move code from the corresponding branch of the conditional to it. Then replace the conditional with the relevant method call. The result is that the proper implementation will be attained via polymorphism depending on the object class.
Define Introduce Parameter Object
Description: Your methods contain a repeating group of parameters.
Smell: Data clumps, long parameter list, long method, primitive obsession
Fix: Replace these parameters with an object.
