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March 3, 2010 - (>= v1_8_6_287)
4 thanks

makedirs(path) to create file path

mkdir will only create a single directory on an existing path. If you want to create a full path, like the `mkdir -p /full/path` command, use the makedirs method.

1.8: File.makedirs(path) 1.9: FileUtils.makedirs(path)

February 27, 2010
4 thanks

Caveat when using dynamic layouts

Worth noting that if you have a controller which inherits from another controller which has a layout, and in this child controller you’re determining the layout at runtime using a method for specific actions, the other actions you are excluding will not inherit the layout from the parent controller.

For example, if you’ve got this

class BaseController < ApplicationController
  layout "public"
end
class OrdersController < BaseController
  layout :determine_layout, :only => :new
  # index, show, new, create, edit, update, destroy ...
end

then OrdersController#index, #show, and #edit won’t get the “public” layout – in fact they won’t get a layout at all. So you’ll need to do this instead:

class OrdersController < BaseController
  layout :determine_layout, :only => :new
  layout "public", :except => :new
  # ...
end
February 26, 2010
3 thanks

default_scope on create

If you specify :conditions in your default_scope in form of a Hash, they will also be applied as default values for newly created objects. Example:

class Article
  default_scope :conditions => {:published => true}
end

Article.new.published? # => true

However:

class Article
  default_scope :conditions => 'published = 1'
end

Article.new.published? # => false
February 23, 2010
3 thanks

Easy workaround for missing :through option

Note that belongs_to does not support :through option like has_many (although IMHO it would make sense in some cases), but you can easily simulate it with delegate.

For example:

class Person < ActiveRecord::Base
  belongs_to :team
  ...
end
class Task < ActiveRecord::Base
  belongs_to :person
  delegate :team, :to => :person
end

There is of course more ways to do it, but this seems to be the easiest to me.

February 19, 2010
8 thanks

Hash#except

Note that the ActiveSupport library provides the except and except! methods, which return the Hash minus the given keys. So you don’t need to write your own wrapper if you happen to be using Rails or ActiveSupport as a stand-alone library:

http://apidock.com/rails/ActiveSupport/CoreExtensions/Hash/Except/except

February 16, 2010 - (>= v2.1.0)
3 thanks

Extract the aggregated scoping options

If you want to get the aggregated scoping options of a chain of named scopes use ActiveRecord::Base.current_scoped_methods

It works in the fashion of:

Shirt.red.medium.alphabetical.current_scoped_methods
# ==>
{
  :create => {}, 
  :find => {
    :conditions => {:color => 'red', :size => 'medium'}, 
    :order => 'shirts.name ASC'
  } 
}
February 11, 2010
4 thanks

reload equivalent for models

The reset_column_information method provides a similar function for the model itself. Most useful during migrations.

February 5, 2010
3 thanks

Rmoving preceding 0's

In most *nix system, adding a - after the % will remove preceding 0s.

So %-d for a single digit day, or %-I for a single digit hour, etc.

January 30, 2010
3 thanks

Paying attention to query parameters

Standard action caching ignores query parameters, which means you’d get the same results for a URL with and without query parameters if it was action cached. You can make it pay attention to them by using a custom cache path like so:

caches_action :my_action, :cache_path => Proc.new { |c| c.params }

Or, maybe you want some of the query parameters, but not all to factor into different versions of that action’s cache:

:cache_path => Proc.new { |c| c.params.delete_if { |k,v| k.starts_with?('utm_') } }

Beware of things like pagination if you use expires_in to expire the cache, as pages could get out of sync.

January 27, 2010
3 thanks
January 21, 2010
3 thanks

W3CDTF Format

Here is the formatted string for the W3CDTF datetime format (http://www.w3.org/TR/NOTE-datetime). It has a semicolon in the timezone part, therefore you cannot use ‘%z’:

Time::DATE_FORMATS[:w3cdtf] = lambda { |time| time.strftime("%Y-%m-%dT%H:%M:%S#{time.formatted_offset}") }
January 20, 2010
4 thanks

Using html text instead of default response

If you have a string containing html and want to assert_select against it, as the doc states you have to pass in an element (HTML::Node) as the first argument. You can do something like this:

doc = HTML::Document.new('<p><span>example</span></p>')
assert_select doc.root, 'span'
January 20, 2010
3 thanks
January 16, 2010 - (>= v2.2.1)
7 thanks

Pretty way to test for current environment

You can check your current Rails environment using nice methods such as:

Rails.env.development?
Rails.env.test?
Rails.env.production?
Rails.env.your_custom_environment?
January 15, 2010
3 thanks

Use this in controllers

Sometimes you’re gonna need this in controllers. Just put this in the controller:

include ActionView::Helpers::NumberHelper
January 6, 2010
6 thanks

Doesn't return nil if the object you try from isn't nil.

Note that this doesn’t prevent a NoMethodError if you attempt to call a method that doesn’t exist on a valid object.

a = Article.new

a.try(:author) #=> #<Author ...>

nil.try(:doesnt_exist) #=> nil

a.try(:doesnt_exist) #=> NoMethodError: undefined method `doesnt_exist' for #<Article:0x106c7d5d8>

This is on Ruby 1.8.7 patchlevel 174

December 28, 2009
4 thanks

Attribute names are Strings, not Symbols

Another possible gotcha – the returned hash keys are of type String, not Symbol:

user.attributes["login"] # => "joe"
user.attributes[:login] # => nil
December 18, 2009
4 thanks

Version Ranges

To specify a version range, use array syntax like this:

config.gem 'paperclip', :version => ['>= 2.3.1.1', '< 3.0']

The example will, of course, match any version 2.3.1.1 or newer up until (not including) 3.0 or later.

November 23, 2009
3 thanks

Make directory if not exists

If the directory already exists, mkdir raises exception. To prevent this:

Dir.mkdir(dir) unless File.exists?(dir)
November 18, 2009 - (>= v1_8_6_287)
4 thanks

Example

code:

class Klass
  def set(string)
    var_name = "@#{string}"  # the '@' is required
    self.instance_variable_set(var_name, 'bar')
  end
  def puts_foo
    puts @foo
  end
end
k = Klass.new
k.puts_foo  # nil
k.set('foo')
k.puts_foo  # 'bar'
November 12, 2009
8 thanks

Use hash form of updates argument

The examples are unfortunate, because passing a string as the updates argument is an invitation to SQL injection attacks. Don’t do this!

Billing.update_all("author='#{author}'")

Use the hash form of updates instead:

Billing.update_all(:author => author)

Then the SQL adapter will quote everything safely. Even if [you think] you’re sure there’s no quoting issue, it’s better to cultivate the habit of using the hash form just in case you missed something.

Same with conditions–use the hash or array form rather than a string if there are variables involved.

BTW, to do this and give options, of course you’ll need to put the braces back in:

Billing.update_all({:author => author},
                   ['title like ?', "#{prefix}%"])
November 5, 2009
8 thanks

define_method with parameters

Just to be clear, you can do this:

define_method(:my_method) do |foo, bar| # or even |*args|
  # do something
end

This means same as:

def my_method(foo, bar)
  # do something
end

If you want to define method with parameters that have default values, you need to get a bit more creative and do something like this:

define_method(:my_method) do |foo, bar|
  bar ||= {}
  # do something
end
November 5, 2009 - (>= v2.1.0)
7 thanks

Named scope better than conditions

In modern versions of Rails, in most cases a named_scope is a better alternative to using :conditions on your has_many relations. Compare:

class User
  has_many :published_posts, :conditions => {:published => true}
end
user.published_posts

with:

class Post
  named_scope :published, :conditions => {:published => true}
end
class User
  has_many :posts
end
user.posts.published

It’s better because the Post’s logic (“am I published?”) should not be coupled within User class. This makes it easier to refactor: e.g. if you wanted to refactor the boolean :published field into a :status field with more available values, you would not have to modify User class. Having to modify User when you refactor some implementation detail of Post class is clearly a code smell.

This also applies to :order, :group, :having and similar options.

October 30, 2009
7 thanks

How FormBuilders work

What, you were expecting documentation? :)

An excellent survey of how FormBuilders work is here:

http://code.alexreisner.com/articles/form-builders-in-rails.html

October 28, 2009
7 thanks

#blank?

The opposite of this is #blank?

October 27, 2009
4 thanks

#present?

The opposite of this is #present?

October 22, 2009 - (>= v2.1.0)
4 thanks

Update statement won't include all attributes with ActiveRecord::Dirty

With the addition of ActiveRecord::Dirty, the update statement will only feature changed columns, as opposed to the comment of railsmonk below.

October 20, 2009
3 thanks

See Dir#glob

See glob for more usage information and comments.

October 15, 2009
4 thanks

Have check_box checked by default

In addition to comment below, you can make a column with default value so in your forms it will be enabled by default and behave correctly with validation errors unlike :checked => true

in your migration

add_column :accounts, :ssl_enabled, :boolean, :default => 1
October 7, 2009
4 thanks

Hash#without

Here’s a small helper for doing the “opposite” of this method:

class Hash
  def without(*keys)
    cpy = self.dup
    keys.each { |key| cpy.delete(key) }
    cpy
  end
end

h = { :a => 1, :b => 2, :c => 3 }
h.without(:a)      #=> { :b => 2, :c => 3 }
h.without(:a, :c)  #=> { :b => 2 }