code smells

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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