Code Smell

• Code smells [Fowler, Beck]
• Actual term used
• Indicates the need for a refactoring
• Typically based on developer intuition
• We will look at a few examples

Primitive Obsession

Primitive Obsession

Use of primitive types when an object is needed, e.g., array, Money, Data, etc.

• Hinders: comprehension, reuse
• Main Refactoring: Replace Data Value with Object, Replace Type Code with {Class, Subclasses, State/Strategy}
• For many fields: Extract Class
• For many parameters: Introduce Parameter Object
• For arrays: Replace Array with Object

Primitive Obsession

Long Parameter Lists₁

• Difficult to use a call or get parameters in the correct order
• Difficult to read and interpret what the call does
• Has boolean parameters
• Has optional, null parameters

Long Parameter Lists

Too many parameters

• Functionality is wrong, or not enough use of fields
• Hinders: comprehension, use, adding parameters
• Main Refactoring: Replace Parameter with Method, Preserve Whole Object, Introduce Parameter Object

Data Clumps

Data Clumps

Bunches of data that always hang around together

• Hinders: comprehension, reuse
• For fields: Extract Class
• For method signatures: Introduce Parameter Object, Preserve Whole Object

Character

Switch Statements

Most switch statements should be replaced by polymorphism

• Hinders: comprehension, reuse
• Secondary Refactorings: Extract Method, Move Method
• Main Refactorings: Replace Type Code with {Subclasses, State/Strategy}, Replace Conditional with Polymorphism
• When polymorphism is overkill: Replace Parameter with Explicit Methods
• Case is Null: Introduce Null Object

Ref: Replace Type Code with Subclasses