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Software Engineering Modern Approaches Chapter 24. Refactoring
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Using a Refactoring Wizard
Shift/Alt/R © 2010 John Wiley & Sons Ltd.
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Fowler’s Refactoring Taxonomy
Big Refactorings Composing Methods Moving Features Between Objects Organizing Data Dealing With Generalization Simplifying Conditional Expressions Making Method Calls Simpler © 2010 John Wiley & Sons Ltd.
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Big Refactorings 1: Tease Apart Inheritance *
Employee before SoftwareEmp MaintceEmp ClericalEmp FulltimeSoftwareEmp FulltimeMaintceEmp FulltimeClericalEmp ParttimeSoftwareEmp ParttimeMaintceEmp ParttimeClericalEmp RetiredSoftwareEmp RetiredMaintceEmp RetiredClericalEmp *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 1: Tease Apart Inheritance *
Employee before SoftwareEmp MaintceEmp ClericalEmp FulltimeSoftwareEmp FulltimeMaintceEmp FulltimeClericalEmp ParttimeSoftwareEmp ParttimeMaintceEmp ParttimeClericalEmp RetiredSoftwareEmp RetiredMaintceEmp RetiredClericalEmp after Employee Status SoftwareEmp MaintceEmp ClericalEmp Fulltime Parttime Retired *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 2*: Convert Procedural Design to Objects
before Control startGame() displayCharacter() moveCharacter() VideoGame GameCharacter *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 2*: Convert Procedural Design to Objects
before Control startGame() displayCharacter() moveCharacter() VideoGame GameCharacter after GameCharacter display() move() VideoGame start() *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 3*: Separate Domain from Presentation
Account name balance … displayStandard() displayHTML() Big Refactorings 3*: Separate Domain from Presentation before *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 3*: Separate Domain from Presentation
Account name balance … displayStandard() displayHTML() Big Refactorings 3*: Separate Domain from Presentation before StandardAccountGUI display () after Account name balance … HTMLAccountGUI display () *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 4*: Extract Hierarchy
before Project *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Big Refactorings 4*: Extract Hierarchy
before Project after Project SoftwareEngineeringProject CustomerEntertainmentProject MobileApplication DesktopApplication *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Organizing Data 3* Replace Record with Data Class
Simplest object with private data field, accessor Replace Type Code with Class Account … type before AccountType REGULAR: AccountType BIG_DISCOUNT: AccountType SMALL_DISCOUNT: AccountType Account … after *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Replace Type Code with Subclass
Organizing Data 4* Replace Type Code with Subclass Replace Type Code with State/Strategy Account … type Account … type *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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WholesaleAccountType
Organizing Data 4* Replace Type Code with Subclass Replace Type Code with State/Strategy Account … Account … type RegularAccount WholesaleAccount Account … AccountType … Account … type RegularAccountType WholesaleAccountType *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Dealing with Generalization 2*
Extract Subclass Extract Superclass Order quantity discount minimum type Manager name salary numSupervisees Engineer name salary skillSet *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Dealing with Generalization 2*
Order quantity Extract Subclass Extract Superclass Order quantity discount minimum type WholesaleOrder discount minimum Employee name salary Manager name salary numSupervisees Engineer name salary skillSet Manager numSupervisees Engineer skillSet *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Dealing with Generalization 3*
Extract Interface Collapse Hierarchy Inherited class not special enough Manager name salary numSupervisees billRate Engineer name salary skillSet billRate *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Dealing with Generalization 3*
Extract Interface Collapse Hierarchy Inherited class not special enough Employee getName() getSalary() Billable getRate() Manager name salary numSupervisees billRate Engineer name salary skillSet billRate Manager numSupervisees Engineer skillSet *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Dealing with Generalization 4*: Form Template Method
BicycleAssemblyInstructions writeBikeInstructions() TricycleAssemblyInstructions writeTrikeInstructions() *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Dealing with Generalization 4*: Form Template Method
AssemblyInstructions writePrep() writeSafety() writeWrapUp() writeManual() Dealing with Generalization 4*: Form Template Method BicycleAssemblyInstructions writePrep() writeSafety() writeWrapUp() BicycleAssemblyInstructions writeBikeInstructions() TricycleAssemblyInstructions writeTrikeInstructions() TricycleAssemblyInstructions writePrep() writeSafety() writeWrapUp() *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Fowler: Dealing with Generalization*
Replace Inheritance with Delegation Replace Delegation with Inheritance Record lastChanged() Account *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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Fowler: Dealing with Generalization*
Replace Inheritance with Delegation Replace Delegation with Inheritance Record lastChanged() record.lastChanged() Account record Account lastChanged() Record lastChanged() *Fowlers’ taxonomy © 2010 John Wiley & Sons Ltd.
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