Elaine Naomi elainenaomi

When should you use DateTime and when should you use Time?

It's a common misconception that [William Shakespeare][1] and [Miguel de Cervantes][2] died on the same day in history - so much so that UNESCO named April 23 as [World Book Day because of this fact][3]. However because England hadn't yet adopted [Gregorian Calendar Reform][4] (and wouldn't until [1752][5]) their deaths are actually 10 days apart. Since Ruby's Time class implements a [proleptic Gregorian calendar][6] and has no concept of calendar reform then there's no way to express this. This is where DateTime steps in:

>> shakespeare = DateTime.iso8601('1616-04-23', Date::ENGLAND)
=> Tue, 23 Apr 1616 00:00:00 +0000
>> cervantes = DateTime.iso8601('1616-04-23', Date::ITALY)
=> Sat, 23 Apr 1616 00:00:00 +0000

Rails naming conventions

General Ruby conventions

Class names are CamelCase.

Methods and variables are snake_case.

Methods with a ? suffix will return a boolean.

Remove MySQL completely

Open the Terminal
Use mysqldump to backup your databases
Check for MySQL processes with: ps -ax | grep mysql
Stop and kill any MySQL processes
Analyze MySQL on HomeBrew:
```
brew remove mysql
```

git add -p is your friend

git add -p is basically "git add partial (or patch)"

Patch mode allows you to stage parts of a changed file, instead of the entire file. This allows you to make concise, well-crafted commits that make for an easier to read history. This feature can improve the quality of the commits. It also makes it easy to remove parts of the changes in a file that were only there for debugging purposes - prior to the commit without having to go back to the editor.

It allows you to see the changes (delta) to the code that you are trying to add, and lets you add them (or not) separately from each other using an interactive prompt. Here's how to use it:

from the command line, either use

git add -p

Pry Cheat Sheet

Youtube Tutorial 2013

Command Line

pry -r ./config/app_init_file.rb - load your app into a pry session (look at the file loaded by config.ru)
pry -r ./config/environment.rb - load your rails into a pry session

Debugger

Chapter 1 - Object Oriented Design

The purpose of design is to allow you to do design later, and it's primary goal is to reduce the cost of change.

SOLID Design:

Single Responsibility Principle: a class should have only a single responsibility
Open-Closed Principle: Software entities should be open for extension, but closed for modification (inherit instead of modifying existing classes).
Liskov Substitution: Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program.
Interface Segregation: Many client-specific interfaces are better than one general-purpose interface.

This text now lives at https://github.com/MarcDiethelm/contributing/blob/master/README.md. I turned it into a Github repo so you can, you know, contribute to it by making pull requests.

Contributing

If you want to contribute to a project and make it better, your help is very welcome. Contributing is also a great way to learn more about social coding on Github, new technologies and and their ecosystems and how to make constructive, helpful bug reports, feature requests and the noblest of all contributions: a good, clean pull request.

Falsehoods programmers believe about prices

You can store a price in a floating point variable.
All currencies are subdivided in 1/100th units (like US dollar/cents, euro/eurocents etc.).
All currencies are subdivided in decimal units (like dinar/fils)
All currencies currently in circulation are subdivided in decimal units. (to exclude shillings, pennies) (counter-example: MGA)
All currencies are subdivided. (counter-examples: KRW, COP, JPY... Or subdivisions can be deprecated.)
Prices can't have more precision than the smaller sub-unit of the currency. (e.g. gas prices)
For any currency you can have a price of 1. (ZWL)
Every country has its own currency. (EUR is the best example, but also Franc CFA, etc.)

On Tue, Mar 12, 2013 at 1:26 PM, Martin Fowler [email protected] wrote:

The term pops up in some different places, so it's hard to know what it means without some context. In PoEAA I use the pattern Service Layer to represent a domain-oriented layer of behaviors that provide an API for the domain layer. This may or may not sit on top of a Domain Model. In DDD Eric Evans uses the term Service Object to refer to objects that represent processes (as opposed to Entities and Values). DDD Service Objects are often useful to factor out behavior that would otherwise bloat Entities, it's also a useful step to patterns like Strategy and Command.

It sounds like the DDD sense is the sense I'm encountering most often. I really need to read that book.

The conceptual problem I run into in a lot of codebases is that rather than representing a process, the "service objects" represent "a thing that does the process". Which sounds like a nitpicky difference, but it seems to have a real impact on how people us

	var collectionNames = db.getCollectionNames(), stats = [];
	collectionNames.forEach(function (n) { stats.push(db[n].stats()); });
	stats = stats.sort(function(a, b) { return b['size'] - a['size']; });
	for (var c in stats) { print(stats[c]['ns'] + ": " + stats[c]['size'] + " (" + stats[c]['storageSize'] + ")"); }