Patterns, Code Smells, and The Pragmatic

Programmer

JMac@gonedark

The journey from apprentice to craftsman

JMac != expert

JMac == craftsman

– @gonedark

“In programming, communication is king.”

– @Selkirk

“The Reading List”

Agile Software Development

Agile Testing

Analysis Patterns

Art of Capacity Planning

Art of Software Testing

Clean Code

Code Complete 2

Continuous Delivery

Continuous Integration

Design Patterns

Domain Driven Design

Even Faster Web Sites

Experiences of Test Automation

Extreme Programming Explained: Embrace Change

Founders at Work

Fundamentals of Object Oriented Design in UML

Growing Object-Oriented Software Guided by Tests

High Performance MySQL

High Performance Web Sites

Implementation Patterns

JavaScript The Good Parts

The Reading List

http://bit.ly/1bbslO0

The Pragmatic Programmer

Andrew Hunt David Thomas

Tips

• “Always use source control”

• “Don’t live with broken windows”

• “Don’t program by coincidence”

• “Work with a user to think like a user”

Stories

• Tracer Bullets

• Stone Soup and Boiled Frogs

• Rubber Ducking

– TA from CS 181

“Please stop coming to me saying, ‘gcc is broken’. It’s not. gcc has been compiling C for 30 years. You have for a month. Your code is

broken.”

– Tip #26 from The Pragmatic Programmer

“‘select’ isn’t broken.”

Invest in your Knowledge Portfolio

• Learn a new language every year

• Read books related to your field

• Be active in your community

• Experiment with new technology

• Stay current

Design Patterns

Elements of Reusable Object-Oriented Software

Erich Gamma Richard Helm

Ralph Johnson John Vlissides

Catalog of Patterns

• Creational Patterns: Builder, Singleton, Factory…

• Structural Patterns: Adapter, Facade, Decorator…

• Behavioral Patterns: Command, Iterator, Observer…

– @DHH

“It becomes quite compelling to apply these fancy ever more complicated patterns to

something… and it works, but the code isn’t better. And by ‘better’ I mean ‘clear’.”

– @gonedark

“Don’t play design pattern bingo.”

• Router

• Controller

• DataManager

• DataCreator

• JobQueue

• Job

• Repository

• Model

“…there’s a big conversation about decompiling everything and nothing should

depend on any concrete class and everything should be talking through narrow interfaces

because you just never know when you’ll need to swap out your database for an API so your

application should be ignorant of that and blah blah blah.” – @AdamWathan

– YAGNI a principle of Extreme Programming

“You aren't gonna need it.”

Refactoring Improving the Design of

Existing CodeMartin Fowler

Code Smells

• Duplicate Code

• Long Method

• Feature Envy

• Primitive Obsession

• Lazy Class

• Speculative Generality

Refactoring

– Martin Fowler

“Refactoring is the process of changing a software system in such a way that it does not

alter the external behavior of the code yet improves its internal structure.”

– Martin Fowler

“Refactoring is the process of changing a software system in such a way that it does not

alter the external behavior of the code yet improves its internal structure.”

– Martin Fowler

“… the program works. Is [refactoring] not just an aesthetic judgement, a dislike of ugly code? It is, until we want to change the system. The

compiler doesn't care whether the code is ugly or clean. But when we want to change the

system, there is a human involved, and humans do care.”

Refactor Process

• small change

• test

• repeat

Decompose Conditional

if (date.before(x) || date.after(y)) { charge = quantity * winterRate } else { charge = quantity * summerRate }

Decompose Conditional

if (isWinter(date)) { charge = winterCharge() } else { charge = summerCharge() }

Implementation Patterns

Kent Beck

Programming Values

• Communication

• Simplicity

• Flexibility

Programming Principles• Local Consequence

• Minimize Repetition

• Logic and Data Together

• Symmetry

• Declarative Expression

• Rate of Change

Symmetry

process() { input() count++ output() }

Symmetry

process() { input() increment() output() }

Symmetry

process() { input() tally() output() }

Rate of Change

setAmount(value, currency) { this.value = value this.currency = currency }

Rate of Change

setAmount(value, currency) { this.amount = new Money(val, cur) }

Programming Costs

cost[total] = cost[develop] + cost[maintain]

cost[maintain] = cost[understand] + cost[change]

+ cost[test]

+ cost[deploy]

– Kent Beck

“Programmers read more code than they write.”

– Kent Beck

“Programming would be more effective if programmers spent less time on the mundane,

repetitive parts of their job so they had more time to spend doing a good job of solving truly

unique problems.”

– The Audience

“Cool book report. So, what now?”

4 simple practices

#1 Adopt a Coding Standard

– @gonedark

“A coding standard is not about curly brace placement or spaces versus tabs. It’s about

signal versus noise.”

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#2 Write Good Enough Software

– Antoine de Saint Exupéry

“…perfection is attained not when there is nothing more to add, but when there is nothing

more to remove.”

#3 Remove Comments

“[comments are] a delicate matter, requiring taste and judgment. I tend to err on the side of

eliminating comments, for several reasons. First, if the code is clear, and uses good type names and variable names, it should explain

itself. Second, comments aren’t checked by the compiler, so there is no guarantee they’re right,

especially after the code is modified. A misleading comment can be very confusion.

Third, the issue of typography: comments clutter code.”

– Rob Pike

#4 Avoid else

testFunc(expr) { ret = false if (expr) { ret = true } else { ret = false }

return ret }

testFunc(expr) { ret = false if (expr) { ret = true } else { ret = false }

return ret }

testFunc(expr) { ret = false if (expr) { ret = true }

return ret }

testFunc(expr) { if (expr) { return true }

return false }

testFunc(expr) { return !!expr }

– @gonedark

“In programming, communication is king.”

Resources• The Reading List - http://bit.ly/1bbslO0

• What is good code? - http://bit.ly/1C535D7

• Ineffective Coding Habits - http://bit.ly/1HGgipm

• Removing Comments - http://bit.ly/1JG8n8J

• Basically anything I’ve tweeted in the last month - @gonedark