42

Problem

You are using a polymorphic association in your application, and you would like to know how exactly the as declaration in your model has_many is used in the SQL by ActiveRecord. So following the example in the Rails Guides with the following models:

class Picture < ActiveRecord::Base
  belongs_to :imageable, :polymorphic => true
end

class Employee < ActiveRecord::Base
  has_many :pictures, :as => :imageable
end

class Product < ActiveRecord::Base
  has_many :pictures, :as => :imageable
end

Solution

ActiveRecord uses the as in the model declaration as a guide to find the foreign id key in the polymorphic association, by adding the _id to the :as name. So following the
example above the query for the product would be:

SELECT `images`.*
FROM `images`
WHERE (`ratings`.imageable_id = 289
      AND `images`.imageable_type = 'Product')

Problem

You would like to have a formatted output in your console when you want to have a look at an objects methods for example (o.methods).

Solution

You can use the y before the o.methods like below:

y o.methods

Problem
After reading this post here, to be able to use the Cucumber table trasformatios feature to build objects in your cucumber tests, you would like to use FactoryGirl instead of the standard model.
The reason for using FactoryGirl could be that your model needs a few more attributes (mandatory fields), that you don’t want to specify in your cucumber table, but you want the factory to take care of them.

Solution
The only difference would take place in the transformation step.
So if you would originally have the following:

Transform /^table:Vehicle,User,Start,End$/ do |table|
  table.hashes.map do |hash|
    vehicle = Vehicle.create!({:regno => hash['Vehicle']})
    user = User.create!({:first_name => hash['User']})
    booking = Booking.create!({:start_at => hash['Start'],
                               :end_at => hash['End']})
    {:vehicle => vehicle, :user => user, :booking => booking}
  end
end

and for example your user has also fields like password, date of birth, that are mandatory in the model validations, you would put them in your factory define declaration like:

Factory.define(:user) do |u|
u.first_name "Name"
u.last_name "Lastname"
u.address1 "Address1"
u.address2 "Line 2"
u.address3 "Line 3"
u.zip "1111"
u.city "City"
u.sequence(:email) {|n|"teste#{n}@test.com"}
u.profile_picture File.open(File.join(Rails.root,"features/fixtures/user.png"))
u.password "password"
end

and replace the tranformation to:

Transform /^table:Vehicle,User,Start,End$/ do |table|
table.hashes.map do |hash|
vehicle = Factory(:vehicle, :regno => hash['Vehicle'])
user = Factory(:user,:first_name => hash['User'])
booking = Factory(:booking, :start_at => hash['Start'],
:end_at => hash['End'])

{:vehicle => vehicle, :user => user, :booking => booking}
end
end

The actual step would similar to the one in the blog article:

Given /^the following bookings?:$/ do |table|
# table is a Cucumber::Ast::Table
table.each do |group|
booking = group[:booking]
associations = {:vehicle => group[:vehicle], :user => group[:user]}
booking.update_attributes(associations)
end
end

Problem
You would like to use a random password in ruby. Most solutions describe using the Digest library (Digest::SHA1).

Solution
According to the post here, you can achieve the same by using ActiveSupport’s secure_random library.
To use it in Ruby outside Rails use:

require 'active_support/secure_random'
ActiveSupport::SecureRandom.hex(10)
ActiveSupport::SecureRandom.base64(10)

and inside rails:

SecureRandom.hex(10)

Problem
After upgrading your server to use rvm and Ruby 1.9 you get the following error when you are trying to access certain parts of your redmine installation:

passenger ArgumentError (invalid byte sequence in US-ASCII)

Solution
If you follow the instruction posted here, you can add the following to your redmine’s “RAILS_ROOT/config/initializers/string_encodings.rb”:

Encoding.default_external = 'UTF-8'

and restart your application

Problem
You would like to (re)-install passenger after a system wide rvm installation, but you only have the mod_passenger.c file and not the .so after the gem installation.

Solution
Make sure that after using gem install passenger you also use the command to install the apache2 passenger module:

passenger-install-apache2-module

you should then be able to see the .so file and add it to your /etc/apache2/mods-available/passenger.load

Problem
You want to add a hidden field that contains a url parameter in a rails form.

Solution
Use the following in your form view (ie new.html.erb):
<%= f.hidden_field :hidden_field_name, { :value => params[:url_param_value]} %>

Problem
When you try to replace prototype with jquery in your Rails 3.0.x application, by using the command described in the Agile Web development book:

rails generate jquery:install --ui --force

you get the following error:

Could not find generator jquery:install

Solution
You would need to follow the steps below:

1. Add gem “jquery-rails”, “~> 1.0.13″ in your Gemfile, and run bundle install
2. run the command described above: rails generate jquery:install –ui –force

Now you should be able to see something like:

remove public/javascripts/prototype.js
remove public/javascripts/effects.js
remove public/javascripts/dragdrop.js
remove public/javascripts/controls.js
copying jQuery (1.6.2)
create public/javascripts/jquery.js
create public/javascripts/jquery.min.js
copying jQuery UI (1.8.14)
create public/javascripts/jquery-ui.js
create public/javascripts/jquery-ui.min.js
copying jQuery UJS adapter (cd619d)
remove public/javascripts/rails.js
create public/javascripts/jquery_ujs.js

Problem
You have an edit form that displays a value in a format (ie dates) that you want to modify by using a helper method (ie display_datetime).

Solution
According to the suggestion here, you can use the following in your view:

<%= f.text_field :date_field_to_format, :value => display_datetime(f.object.date_field_to_format) %>

Problem
You would like to test your model associations in an RSpec model spec, to make sure that they are correctly set up.

Solution
After some Google searching and coming across this article here, ended up using the second method described there with the reflect_on_association method, as it doesn’t need the inclusion of another gem.
So for example to to test multiple has_many or belongs_to associations in your model rspec you could use something like:
context "check associations" do
# belongs_to associations
%w{bel_to1 bel_to2}.each do |bt|
it "should belong to #{bt}" do
m = Model.reflect_on_association(:"#{bt}")
m.macro.should == :belongs_to
end
end
# has_many associations
%w{has_many1 has_many2 has_many3}.each do |hm|
it "should have many #{hm}" do
m = Model.reflect_on_association(:"#{hm}")
m.macro.should == :has_many
end
end
end