Interesting Things

• Last week, we discovered that Ruby 1.9′s require is unnecessarily slow, and that there’s a patch targeted for 1.9.3. Until then, Dave G. says, you can use the following to patch your Ruby 1.9.2 using RVM:

  curl https://raw.github.com/gist/1008945/7532898172cd9f03b4c0d0db145bc2440dcbb2f6/load.patch > /tmp/load.patch
  rvm get head   # always good to make sure you're up to date with RVM
  rvm reload
  rvm install ruby-1.9.2-p180 --patch /tmp/load.patch -n patched
  rvm use ruby-1.9.2-p180-patched
  

  [from https://gist.github.com/1008945/]

Events

• Girl Develop It: The first session of the June section of Girl Develop It on Javascript and jQuery has been bumped to next Thursday, June 16th. There’s still room to sign up!

Ask for Help

“How can I validate the presence of a boolean field?”

false.present? is false, so validates :a_boolean_field, presence: true will not cause a validation error when the field’s value is false. What you’re really trying to do, probably, is to validate that it’s not nil.

The best solution we had was to use validates :a_boolean_field, inclusion: { in: [true, false], message: "must be specified" }. The custom message is needed because the default inclusion message looks weird to the user here.

How can we integration-test CarrierWave uploads to S3? Can we stub out S3?

Two suggestions: use VCR to mock the S3 conversation or use Park Place to provide a fake S3 and check the results afterwards.

Interesting Things

• Given a Rails belongs_to association reflection, how do you get the name of the foreign key column? It’s not what you might think:

  class Person < ActiveRecord::Base
    belongs_to :best_friend, class_name: "Person"
  end
  
  
  Person.reflect_on_association(:best_friend).primary_key_name  # => "best_friend_id"
  

  Why is it called primary_key_name if it’s a foreign key? No idea. But it is.

  Note: The reflection also has an association_foreign_key. This is not what it’s for. In this case, for instance,

  Person.reflect_on_association(:best_friend).association_foreign_key  # => "person_id"
  

Pivotal Tracker is a founding member of NetworkedHelpDesk.org, a new initiative to help “create a seamless communication stream among multiple partners and suppliers to deliver an awesome customer experience.”

Led by Zendesk, NetworkedHelpDesk.org is on open application programming interface (API) that will make it easier to connect disparate systems in areas such as project management, customer relationship management, issue tracking, and customer support.

We’re excited to be part of this initiative, and look forward to building richer, bi-directional integrations between Pivotal Tracker and other applications in the product ecosystem that help our customers collaborate across their entire organization.

If you’re interested in joining the initiative, check out the API, and join today!

Interesting Things

• min_by / max_by: Ian points us towards Enumerable‘s handy #min_by and #max_by. Want to get the string in a collection whose second-to-last character is earliest in the alphabet?

  ["ayx", "zbaaaz"].min_by { |s| s[-2] }  # => "zbaaaz"
  

• keep_if: On the subject of collections, Kris points out Ruby 1.9′s Array#keep_if (note the missing bang at the end), which mutates the array to remove things for which the block returns false. For example,

  a = ["ayx", "zbaaaz"]
  a.keep_if { |s| s.length < 4 }
  a                                       # => ["ayx"]
  

  Another method, Array#select! behaves very similarly. The only difference is that when it doesn’t change the array, #select! returns nil while #keep_if returns the array. Returning nil matches the behavior of other mutators like String#sub!, while #keep_if breaks the pattern. Thus,

  ["ayx", "zbaaaz"].keep_if { |s| s.length < 4 }    # => ["ayx"]
  ["ayx", "zbaaaz"].select! { |s| s.length < 4 }    # => ["ayx"]
  ["ayx", "zbaaaz"].keep_if { |s| s.length < 10 }   # => ["ayx", "zbaaaz"]
  ["ayx", "zbaaaz"].select! { |s| s.length < 10 }   # => nil
  

  It is, perhaps, of questionable value.

• $("textarea").clone(): Ian discovered that when jQuery clones form fields, the clones of input elements retain the values of the originals, while textareas and selects become blank.

• jsFiddle: Sam J. points us towards jsFiddle, a nifty tool for sharing JavaScript snippets. It provides a pane each for JS, CSS, and HTML, and then a pane that shows the results. Then you can share it like a Gist or a Pastie.

Interesting Things

• Using the result of render as an attribute: If you call render in a view, you’ll get back a SafeBuffer, which acts like a String but is trusted and allowed to contain HTML which will not be escaped when it’s placed on the page. If you use this value in a DOM attribute, however, it will be escaped:

  - template = render 'ajaxy_thing/template'
  %ul#ajaxy_things{template: template}
  

  If it weren’t escaped, the contents of template would probably break out of the ul tag early and mess things up.

  One pair tried to extract code like this into a helper, and then do something like:

  template = render('ajaxy_thing/template')
  content_tag(:ul, id: "ajaxy_things", template: template)
  

  Here, it turns out, template is so trusted that its contents are inserted without escaping, which breaks the ul tag. It becomes something like:

  

  which is clearly no good. (In fact, it’s so weird that I had to turn that snippet into an image just to get the blog to display it.)

  When you have a String which is untrusted and you don’t want it to be escaped, you call #html_safe on it. This is the opposite, and it’s not clear how best to do it. The pair decided to make a new String out of it, which worked:

  template = String.new(render('ajaxy_thing/template')) # The new String is not html_safe
  

• TeamCity 6.5 : TeamCity 6.5 is out, but it breaks RVM support. It will return in 6.5.1.

Events

• Girl Develop It will begin its 4-week June section on Javascript and jQuery on Thursday, June 9th. Girl Develop It is a series of programming classes designed to help women enter the software development world and change the ratio. There are still some spots left!