Community contributions, tips, and corrections to the documentation. (1708 notes)
There are no dynamic exists? methods analogous to dynamic finders, which means that while you can do this:
Person.find_by_name('David')
you can't do this:
Person.exists_by_name('David') # DOES NOT WORK
nor this:
Person.exists_by_name?('David') # DOES NOT WORK
However, you can simul...
You might want to do this:
module ActionView module Helpers module TranslationHelper def localize(*args) #Avoid I18n::ArgumentError for nil values I18n.localize(*args) unless args.first.nil? end # l() still points at old definition alias l localize...
+RDONLY+, +TRUNC+, etc... are defined in the File::Constants module which is +include+'d by +IO+ and +File+.
IO.open fd, IO::RDONLY File.open path, File::RDONLY
Though as pointed out above, they are interchangeable.
Non +IO+ errors (+IOError+) are contained in the +Errno+ module. They are the same as those given in open(2), see:
http://www.kernel.org/doc/man-pages/online/pages/man2/open.2.html#ERRORS
== Common Errors
If you have polymorphic relations, e.g.:
class Bookmark < ActiveRecord::Base
belongs_to :thing, :polymorphic => true
belongs_to :owner, :polymorphic => true
end
and you want to ensure that a thing can bookmarked by an owner at most once, you can't do this:
validates_uniqu...
You can also use URI.join to resolve relative and absolute links:
URI.join('http://example.com/', '/example').to_s
# => "http://example.com/example"
URI.join('http://example.com/example', 'test').to_s
# => "http://example.com/test"
URI.join('http://example.com/example/', 'test...
If you want to require file from the same folder, the simplest way is
require File.expand_path('../file-to-require', __FILE__)
If your file is /lib/book.rb
File.expand_path('../page', '/lib/book.rb') => '/lib/page.rb'
When using a restful form helper and you want to use a method other than POST, remember to put the :method in the :html option.
e.g. To send a DELETE request instead of the usual POST (with a nested resource thrown in for good measure) use:
<% form_for [@post, @comment], :html => { :method =>...
Note that it would be better to avoid the alias_method line in the example and just call super.
The documentation above mentions that :autosave => true always saves the association and that it's "off" by default. What it doesn't mention what they mean by "off".
Despite the name and description, it will actually update any changed fields on the model rather than just the desired attribute.
def update_attribute(name, value)
send(name.to_s + '=', value)
save(false)
end
See? Use update_all and pass in the model ID as a condition, instead.
If you want to fetch all records when one column (boolean) is set to nil or false, try this:
Project.all(:conditions => "archived IS NULL OR archived = 'f'")
This does not return nil if the array is empty and n is given.
[].shift(2) # => []
a = []
a.shift(2) # => []
a # => []
If you always want to degrade when JS isn't available you can add something like to environment.rb
module ActionView
module Helpers
module PrototypeHelper
def link_to_remote(name, options = {}, html_options = nil)
html_options ||= {}
html_options[:href]...
Note that to interpolate, the sequences must be inside single quotes: # replace /ll/ with itself 'hello'.gsub(/ll/, '\0') # returns 'hello' 'hello'.gsub(/ll/, "\0") # returns 'he\000o'
In the authentication filter example above, the time condition should be reversed: we only want to find the user if +time+ is still in the future (because it's the valid-until time).
So the example should look like this:
id, time = @verifier.verify(cookies[:remember_me])
if time > Time.no...
in main.rb of sinatra:
at_exit { Application.run! if $!.nil? && Application.run? }
When testing callback methods, try to test the callback chain separate from its implementation.
Say this is your model:
class Project
belongs_to :owner
has_many :milestones
after_save :create_milestones
after_save :notify_owner
private
def notify_owner...
Here is some advice how to call your models in a migration without shooting yourself in the foot:
http://gem-session.com/2010/03/how-to-use-models-in-your-migrations-without-killing-kittens
Basically you can inline models into your migrations to decouple them from changes in your model:
class...