Refactoring 9~10
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This document outlines techniques for simplifying conditional expressions and method calls. For conditional expressions, it describes decomposing conditionals, consolidating expressions, removing duplicate code, replacing conditionals with polymorphism, and introducing null objects. For method calls, it suggests techniques like renaming methods, adding/removing parameters, separating queries from modifications, parameterizing methods, preserving whole objects, replacing parameters with methods, introducing parameter objects, removing setting methods, hiding methods, replacing constructors with factories, and replacing error codes with exceptions.
Refactoring 9~10
- 1. Simplifying Conditional Expression and Making Method Calls Simpler Chris Chen
- 2. honestbee Outline - Simplifying Conditional Expression • Decompose Conditional • Consolidate Conditional Expression • Consolidate Duplicate Conditional Fragments • Remove control flag • Replace Nested Conditional with Guard Clauses • Replace Conditional with Polymorphism • Introduce Null Object
- 3. honestbee Outline - Making Method Calls Simpler • Rename Method • Add Parameter • Remove Parameter • Separate Query from Modifier • Parameterize Method • Replace Parameterize with Explicit Methods • Preserve Whole Object • Replace Parameter with Method • Introduce Parameter Object • Remove Setting Method • Hide Method • Replace Constructor with Factory Method • Encapsulate Downcase • Replace Error Code with Exception
- 5. honestbee Decompose Conditional • You have a complicated conditional (if-then-else) statement. • Extract methods from the condition, then part, and else parts. Before After
- 6. honestbee Consolidate Conditional Expression - Ors • You have a sequence of conditional tests with the same result. • Combine them into a single conditional expression and extract it. Before After
- 7. honestbee Consolidate Conditional Expression - Ands Before After
- 8. honestbee Consolidate Duplicate Conditional Fragments • The same fragment of code is in all branches of a conditional expression. • Move it outside of the expression. Before After
- 9. honestbee Remove Control Flag - break • You have a variable that is acting as a control flag for a series of boolean expressions. • Use a break or return instead Before After
- 10. honestbee Remove Control Flag - return Before After
- 11. honestbee Replace Nested Conditional with Guard Clauses • A method has conditional behavior that does not make clear the normal path of execution. • Use guard clauses for all the special cases. Before After
- 12. honestbee Replace Nested Conditional with Guard Clauses - Reversing the Conditions Conditional Before After
- 13. honestbee Replace Conditional with Polymorphism • You have a conditional that chooses different behavior depending on the type of an object. • Move each leg of the conditional to an overriding method in a subclass. Make the original method abstract.
- 14. honestbee Replace Conditional with Polymorphism Before
- 15. honestbee Replace Conditional with Polymorphism After
- 16. honestbee Introduce Null Object • You have repeated checks for a null value. • Replace the null value with a null object Before
- 18. honestbee Introduce Null Object Step1 Create Null Customer Class If you aren't able to modify the Customer class you can use a testing interface.
- 19. honestbee Introduce Null Object Step 2 Create a Factory Method and force replace Null Object with null case
- 20. honestbee Introduce Null Object Step 3 move default case into Null Object
- 21. honestbee MAKING METHOD CALLS SIMPLER CH10CH9
- 22. honestbee Rename Method Before After • The name of a method does not reveal its purpose. • Change the name of the method.
- 23. honestbee Add Parameter • A method needs more information from its caller
- 24. honestbee Remove Parameter • A parameter is no longer used by the method body.
- 25. honestbee Separate Query from Modifier • You have a method that returns a value but also changes the state of an object. • Create two methods, one for the query and one for the modification. There is a simple example in the book P226
- 26. honestbee Parameterize Method • Several methods do similar things but with different values contained in the method body. • Create one method that uses a parameter for the different values.
- 28. honestbee Replace Parameterize with Explicit Methods • You have a method that runs different code depending on the values of an enumerated parameter. • Create a separate method for each value of the parameter Before After
- 29. honestbee Preserve Whole Object • You are getting several values from an object and passing these values as parameters in a method call. • Send the whole object instead. Before After
- 30. honestbee Replace Parameter with Method • An object invokes a method, then passes the result as a parameter for a method. • The receiver can also invoke this method. Remove the parameter and let the receiver invoke the method Before
- 31. honestbee Replace Parameter with Method Step1 Extract a method
- 32. honestbee Replace Parameter with Method Step 2 Remove Parameter and temp
- 33. honestbee Replace Parameter with Method Step 3 create basic price method and refine get price method
- 34. honestbee Introduce Parameter Object • You have a group of parameters that naturally go together. • Replace them with an object
- 36. honestbee Introduce Parameter Object Step1 Create DateRange Object and put start-date, end-date
- 37. honestbee Introduce Parameter Object Step2 replace original param with DateRange
- 38. honestbee Introduce Parameter Object Step3 add one method includes in DateRange class
- 39. honestbee Remove Setting Method • You have a group of parameters that naturally go together. • Replace them with an object
- 42. honestbee Hide Method • A method is not used by any other class. • Make the method private.
- 43. honestbee Replace Constructor with Factory Method • You want to do more than simple construction when you create an object. • Replace the constructor with a factory method Before After
- 44. honestbee Encapsulate Downcase • A method returns an object that needs to be downcasted by its callers. • Move the downcast to within the method. • These case often appear with methods that return collection or iterator Before After
- 45. honestbee Replace Error Code with Exception • A method returns a special code to indicate an error. • Throw an exception instead. Before After
- 46. honestbee Thanks