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[Rails Tip] DataMapper M:M Association Bug and Workaround

It was confirmed that DataMapper is incorrectly setting table names in SQL JOINs.

So for instance, the following code would generate an SQL error:

type.jobs.all(:"country.name".like => "%#{params[:location]}%")

There is a workaround, however the workaround requires manual looping of the dataset thus produces N+1 queries.

type.jobs.all.reject do |job|
  ! job.country.name.downcase.include?(params[:location].downcase)
end

But at least it works. ;)

[Rails Tip] DataMapper Timestamps Bug and Workaround

It has been confirmed by DataMapper’s core developer Martin Gamsjaeger (snusnu) that it is a bug.

In short, created_[at|on] can be manually overridden, but updated_[at|on] cannot.

The workaround is simple, do it in two steps, for example:

  job = Job.create(
    title: "Web Developer",
    created_at: Time.now - 2
  )
  job.update!(updated_at: Time.now - 1)

Please check the bug ticket to see when it’s getting fixed.

About Me

Fred Wu

Located in Melbourne, Australia, I currently work as a development team lead at SitePoint.

Grew up in Shanghai, China, I quickly became interested in computers and the Internet at the age of 13. I started off by creating simple websites using basic HTML I learnt from reading computer magazines. Later on I worked in online publishing, marketing and web hosting while studying in high school. After being a 'webmaster' for a few years, I began my career in web development and design. I studied Bachelor of Information Technology and Systems at Monash University in Melbourne, Australia. I worked as a web developer at places such as Envato and PlayUp before joining SitePoint.

I am primarily a Ruby and PHP developer as well as a front-end/UI developer. In my spare time I also try to do as much creative designs as I could in order to keep my design skills polished. I also focus strongly on user experience and user interface design.

I am a passionate open source developer who contributes to many of the projects on GitHub, including Ruby on Rails.

Please feel free to shoot me an email if you would like to get in touch. I am also happy to provide estimates and consultancy to any web based projects. You may write to me in English or in Chinese. :)

My Projects

I am the author of the following projects.

Action Throttler - Throttle actions based on configurable duration and limit.
Angel Nest - An open source 'clone' of AngelList.
Datamappify - Turn ActiveRecord into DataMapper (sort of)!
Haml2Slim - Convert Haml templates to Slim templates.
Inherited Resources Views - DRY your view files!
Security Guard - A collection of useful tools for auditing data.
Authlite - A lightweight, flexible Auth module for Kohana.
KThrottler - Throttle actions based on configurable duration and limit.
PHamlP - A bridge between Kohana and PHamlP.
Endless Scroll - Endless / infinite scrolling solution for jQuery.
Inline Confirmation - Less obtrusive confirmation dialogues.
Slideshow Lite - A lightweight slideshow plugin for jQuery.

I am the co-author of the following projects.

RailsConfig - Easiest way to add multi-environment yaml settings to Rails 3.
Slim - A template language similar to Haml.
Ssync - An optimised S3 sync tool using the power of Unix!

I also made contribution to the following projects.

Admin Data - Rails plugin - browse and manage your data using browser.
App Config - Rails plugin that provides application configuration.
Bundler - Ruby gem dependency manager.
Capybara-mechanize - Mechanize driver for Capybara.
Carrierwave - File uploads solution for Rack, Rails, Merb and Sinatra.
Devise - Flexible authentication solution for Rails with Warden.
Delayed Job - Database based asynchronously priority queue system.
Deployer - Simplify the deployment of Ruby on Rails applications.
Inherited Resources - Making controllers inherit all restful actions.
Parallel - Ruby: parallel processing made simple and fast.
Parallel Tests - 2x Testing Speed for RSpec, Test::Unit and Cucumber.
Ruby on Rails - Web development that doesn't hurt.
Rails Templater - Template generator for Ruby on Rails 3 applications.
Sass Rails - Ruby on Rails stylesheet engine for Sass.
Steak - Minimalist acceptance testing on top of RSpec.
Textmate - Command-line package manager for the Textmate editor.
Kohana - An elegant HMVC PHP 5 framework.
Vanilla - An open source discussion forum for the web.
Yii Framework - A high performance PHP framework.
AutoSuggest - Turn regular text input boxes into auto-complete boxes.