code smells
TRANSCRIPT
Software Craftsmanship
Code Smells
Software Craftsmanship Manifesto
“Not only working software, but also well-crafted softwareNot only responding to change, but also steadily adding valueNot only individuals and interactions, but also a community of professionalsNot only customer collaboration, but also productive partnerships”
Technical Debt
Software FinanceSkipping (or deferring) design Borrowing moneyRefactoring (i.e. behavior-preserving design improvements) Repaying principal
Slower development due to code smells Paying interest
Code Smells
• Lost Intent• Inefficient Name• Duplicated Code• Deodorant Comment• Long Method• Large Class• Lazy Class More…
Lost Intent
Just as a traffic sign may be obscured by shrubs, Code that doesn't easily communicate it's author's intention is hazardous: hard to understand, extend and modify.
Lost IntentIntention-Revealing Code Lost Intent
The purpose of the code is clear. Low-level or complex logic obscures the code's purpose.
You can easily find the code you seek. The location of code makes little sense.
Every step of an algorithm is clearly defined.
The steps of the algorithm are blended together.
Lost Intent
Inefficient Name
Where The Streets Have No Name
Inefficient Name
tmp = finder.fetch("0182901");Account theAccount = finder.fetch(transaction.getSource());account = finder.fetch( new StateMatcher("VA") );for(Account item : finder.fetchAll()) { … }
getDrctn()getDir()getDirection()
These are five lines chosen at random from a class.Each is grabbing a fetch result and putting it in a variable of type Account.
Duplicated Code
If you see the same code structure in more than one place, you can be sure that your program will be better if you find a way to unify them.— Refactoring[page 76], Martin Fowler and Kent Beck
Duplicated Code
Deodorant Comment
Comments often are used as a deodorant. — Refactoring [page 87], Martin Fowler and Kent Beck
Deodorant Comment
Comment Guidelines
• Whenever possible make your code express the intent of the comment and remove the comment.
• Comments are to provide intent that is not expressible in code.
• Any comment that duplicates what the code says should be deleted.
Long Method
A long method is too much to digest
Long Method
BeforeLongMethod.txt AfterLongMethod.txt
Large Class
Take on too many responsibilities
Large Class
WebServicesProviderContoller• performValidationCB()• executeBusinessProcessCB()
Lazy Class
A lazy class isn't doing enough to justify its existence.
Lazy Class
Lazy Class
Employee constructor.
Passing Jobs in Employee constructor.
Oddball Solution
When a problem is solved one way throughout a system and the same problem is solved another way in the same system, one of the solutions is the oddball or inconsistent solution.
Oddball Solution
Primitive Obsession
Primitive Obsession exists when code solves a problem using a tool that's too simplistic.
Primitive Obsession
Switch Statement
Most times you see a switch statement you should consider polymorphism. — Refactoring, Martin Fowler and Kent Beck (page 82).
Switch Statement
Move each leg of the conditional to an overriding method in a subclass. Make the original method abstract.
Switch Statement
• Not every occurrence of a switch statement (or if...else if...else if... statements) should be replaced with a polymorphic solution.
Speculative Generality
You get this smell when people say "Oh, I think we will need the ability to do that someday" and thus want all sorts of hooks and special cases to handle things that aren't required. — Refactoring, Martin Fowler and Kent Beck (page 83).
Speculative Generality
Long Parameter List
Methods that take too many parameters produce client code that is awkward and difficult to work with.
Long Parameter List
user = userManager.create(USER_NAME, group, USER_NAME, “test", USER_NAME, LANGUAGE, false, false, new Date(), "blah", new Date());
Conditional Complexity
Conditional logic is innocent in its infancy, when it is simple to understand and contained within a few lines of code. Unfortunately, it rarely ages well. — Joshua Kerievsky, Refactoring to Patterns, page 41.
Conditional Complexity
Combinatorial Explosion
When new combinations of data or behavior further bloat an already bloated design, you've got a Combinatorial Explosion smell.
Combinatorial Explosion
Alternative Classes With Different Interfaces
This subtle smell results when differences in the interfaces of similar classes leads to duplicated code.
Alternative Classes With Different Interfaces
Inappropriate Intimacy
Sometimes classes become far too intimate and spend too much time delving in each others' private parts.— Refactoring [page 85], Fowler and Beck
Inappropriate Intimacy
Indecent Exposure
We don't normally expose wires inside a wall or ceiling.
Indecent Exposure
Refused Bequest
Subclasses get to inherit the methods and data of their parents. But what if they don't want or need what they are given? — Refactoring[page 87], Martin Fowler and Kent Beck
Refused Bequest
Black Sheep
Black Sheep
Solution Sprawl
When code and/or data used to perform a responsibility becomes sprawled across numerous classes, Solution Sprawl is in the air. — Joshua Kerievsky, Refactoring to Patterns, page 43.
Solution Sprawl
Feature Envy
Feature Envy
Temporary Field
An object's field (a.k.a. instance variable) should have meaning during the full lifetime of the object.
Temporary Field
Side Effect
Side Effect
References
• Refactoring: Improving the Design of Existing Code by Martin Fowler
• Refactoring to Patterns by Joshua Kerievsky.• https://elearning.industriallogic.com/gh/subm
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