Olly Legg

Strict Validations in ActiveModel

2012-02-27T00:00:00+00:00

27 Feb 2012

Rails v3.2 has added the concept of strict validations. These validations are ideally suited for data constraints which should always be enforced, but aren't affected by user input. For example, setting the user association to the current_user in the controller.

There are two ways of specifying a validation as strict. Firstly, you can set the :strict option to true. Secondly, you can use the new validates! method.

An ActiveModel::StrictValidationFailed exception is raised if your record fails validation.

class Content
  validates_presence_of :user, strict: true

  # The following is equivalent: 
  # validates! :user, presence: true
end

content = Content.new
content.user = nil
content.valid? 
# => ActiveModel::StrictValidationFailed: can't be blank

Suppressing PostgreSQL NOTICEs

2012-02-21T00:00:00+00:00

21 Feb 2012

For some of our projects at work recently we've switched to using PostgreSQL. Annoyingly it outputs quite a lot of logging by default when creating tables — which clutters up test runs with a lot of unimportant logging.

NOTICE:  CREATE TABLE will create implicit sequence "accounts_id_seq" for serial column "accounts.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "accounts_pkey" for table "accounts"
NOTICE:  CREATE TABLE will create implicit sequence "users_id_seq" for serial column "users.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "users_pkey" for table "users"

The easiest way to globally suppress this output is to change the client_min_messages setting in postgresql.conf to warning. The config file now reads like this:

client_min_messages = warning

If you installed PostgreSQL using Homebrew the config file can be found at /usr/local/var/postgres/postgresql.conf. After updating the config file, run the following to restart the server.

launchctl unload -w ~/Library/LaunchAgents/org.postgresql.postgres.plist
launchctl load -w ~/Library/LaunchAgents/org.postgresql.postgres.plist

Global After Blocks in RSpec; or How to Keep Timecop Happy

2010-01-18T00:00:00+00:00

18 Jan 2010

I recently ran into a problem with a test suite in a Rails application which had me stumped for a while. To sum up briefly a group of test suddenly started failing. What had happened was that Timecop was being set globally and wasn't being reset. This caused problems when a couple of weeks later the tests were run and the times were different to what they were expecting. Although the final solution is very simplistic

One way to fix the test suite would have been to use Timecop's block syntax, for example:

it "should mark the sprint as in the past" do 
  Timecop.freeze(Date.today + 30) do
    sprint.should be_past
  end
end

However I'm not a great fan of this syntax in my tests, I prefer my tests to be more procedural. It also prevents you from stubbing the time in a before block for a group of tests.

The solution I settled with was to add a global after block which resets Timecop after each test. In spec/spec_helper.rb add this simple global after block:

Spec::Runner.configure do |config|
  config.after(:each) do
    Timecop.return
  end
end

What to do this New Year?

2010-01-01T00:00:00+00:00

01 Jan 2010

This is a very cliched, 1st of January, blog post — however it does tie in, very nicely, to my first resolution. Here, for posterity, is a list of the four things I plan to achieve in 2010:

~~Start blogging more often.~~ Start blogging. This blog was started on the 25th March 2009 with the very best of intentions. It has lain dormant ever since. This year I plan to make good on last year's intentions and actually post some content.
I had heard about Code Katas a while back. Having completed my first one last year, after being inspired by Katacasts, I found it very enjoyable and quite useful. Over the coming year I am going to complete some different katas, complete some using different languages and different programming styles.
I've always wanted to be able to take decent photos. To this end I'm going to take more frequent photos this year. I recently saw the excellent Panasonic GF1 review so might invest in one of those. Or I might just start by using my phone. I think taking part in The Daily Shoot would be a good start.
I'm also going to travel round the UK some more over the next year. I want to visit Bath, Cambridge, Exeter and Leeds for starters — mainly because I have sofas to crash on there!

RGB helper method

2009-03-25T00:00:00+00:00

25 Mar 2009

I use Safari for my day to day development and while the ‘Inspect Element’ command has been much improved since earlier versions – I still can’t find out the foreground or background colours in hexadecimal notation.

The following ruby snippet converts from the format that Safari provides into hexadecimal. I find that its really useful to put in .irbrc so that its always available for quick conversions in IRB.

def rgb(*colours)
  colours.inject('#') do |code, colour| 
    code += colour.to_s(16).rjust(2, '0').upcase
  end
end

I’m of the school of thought that every bit of code should be tested, mainly to preserve my sanity, so here are the specs for the following method.

describe "#rgb" do
  it "should convert rgb(0, 0, 0) to '#000000'" do
    rgb(0, 0, 0).should == '#000000'
  end
  
  it "should convert rgb(190, 215, 205) to '#BED7CD'" do
    rgb(190, 215, 205).should == '#BED7CD'
  end
  
  it "should convert rgb(255, 255, 255) to '#FFFFFF" do
    rgb(255, 255, 255).should == '#FFFFFF'
  end
end