Ryan Jackson ryanwebjackson

Working Effectively with Legacy Code

Notes by Jeremy W. Sherman, October 2013, based on:

Feathers, Michael. Working Effectively with Legacy Code. Sixth printing, July 2007.

Foreword:

Software systems degrade into a mess.
Requirements ALWAYS change.
Your goal as a software developer: Create designs that tolerate change.

Intention Revealing Methods

Intention revealing method is simple and yet I see it frequently slip through programmers' code. Developers don't like lengthy methods, or find it inconvenient to read through chubby if-else branches, and if they are nice enough they'll leave comments like those.

If we change spaces by underscores in the comments, delete the comment characters, and define the resulting methods in the same file (as private helpers for example), we get code that explains itself, instead of through verbose long methods, or human code comments which get stale.

Intention revealing methods is the most basic, no brain-teaser, easiest rule that I know. Combine it with Sandi Metz's rule of a maximum of 5 lines per method and you'll get simple code that explains itself, that is a pleasure to read, improving communication and productivity of the team (even when it's only yourself).

Sample Code

JavaScript Static Analysis Tools

Most people are familiar with these three tools:

[JSHint][1]
[JSLint][2]
[Google Closure Linter][3]

The first one is more popular among developers because it is style-agnostic. The other two enforce rules of [Crockford Style][4] and [Google Code Style][5] respectively.

What is your folder-structure preference for a large-scale Node.js project?

0: Starting from Rails

This is the reference point. All the other options are based off this.

|-- app
|   |-- controllers
|   |   |-- admin

	[mergetool]
	prompt = false
	keepBackup = false
	keepTemporaries = false

	[merge]
	tool = winmerge

	[mergetool "winmerge"]
	name = WinMerge

	# xcode-build-bump.sh
	# @desc Auto-increment the build number every time the project is run.
	# @usage
	# 1. Select: your Target in Xcode
	# 2. Select: Build Phases Tab
	# 3. Select: Add Build Phase -> Add Run Script
	# 4. Paste code below in to new "Run Script" section
	# 5. Drag the "Run Script" below "Link Binaries With Libraries"
	# 6. Insure that your starting build number is set to a whole integer and not a float (e.g. 1, not 1.0)

	/**
	* Luhn algorithm in JavaScript: validate credit card number supplied as string of numbers
	* @author ShirtlessKirk. Copyright (c) 2012.
	* @license WTFPL (http://www.wtfpl.net/txt/copying)
	*/
	var luhnChk = (function (arr) {
	return function (ccNum) {
	var
	len = ccNum.length,
	bit = 1,

	for (var i=1; i <= 20; i++)
	{
	if (i % 15 == 0)
	console.log("FizzBuzz");
	else if (i % 3 == 0)
	console.log("Fizz");
	else if (i % 5 == 0)
	console.log("Buzz");
	else
	console.log(i);

	#!/bin/sh

	# Simple iOS build script
	# Written by Aron Bury, 29/11/2011

	appname="AwesomeApp"
	target_name="$appname"
	sdk="iphoneos"
	certificate="iPhone Developer: Joe Blogs"