Update all associations of a Rails model

  @msg_thread.messages.update_all(status: 'read')

Rails scaffold only the controller resource

rails g scaffold_controller users

Share methods between controller and views in Rails

The key is to put methods into ApplicationHelper and call them in the controller

module ApplicationHelper
  def user_unauthorized?
    ...
  end
end

class HomeController < ApplicationController
  def index
    redirect_to '/foo' if view_context.user_unauthorized?
  end
end

Delegate getting name attribute of associations

# Instead of 

def guest_name
  guest.try(:name)
end

# Use delegate

delegate :name, :to => :guest, :allow_nil => true

Difference between includes and joins in rails

Jason please repeat after me ten times.

includes does "LEFT OUTER JOIN" while joins does "INNER JOIN"

Overide default scope in Rails

# Our default scope in question
class Product < ActiveRecord::Base
  default_scope order('created_at desc')
end

# This won't work
Product.order('created_at asc').all

# Method 1: unscoping
Product.unscoped.order('created_at asc').all

# Method 2: with_exclusive_scope
Product.with_exclusive_scope{ Product.order('created_at asc').all }

references: http://ryandaigle.com/articles/2008/11/18/what-s-new-in-edge-rails-default-scoping

Finding source location for a rail method


# Eg. if you want to find source location for DateTime.tomorrow

irb(main):001:0> DateTime.method(:tomorrow).source_location


Sorting searchlogic results

params[:filter][:order] = "ascend_by_created_at"
@search = Note.search(params[:filter])
@notes = @search.all

Functional test for respond_to :json in Rails

# Notes controller

def index
...
  respond_to do |format|
    format.json { render :json => @notes }
  end
end

# Notes functional test

params = {:format => 'json', :title => ...}

get :index, params

notes = JSON.parse(@response.body)
assert_equal note.title, notes[0]['note']['title']

Using curl to post data to a rails app

curl -X POST -d "location[lat]=111&location[lng]=222" http://localhost:3000/users/123/devices/456/locations

However rails require authenticity token. To overcome that just turn forgery protection off.

# config/environment.rb
config.action_controller.allow_forgery_protection = false

Finding uninvoiced fees in rails

# Models

Class InvoiceItem < ActiveRecord::Base
  belongs_to :fee
end

Class Fee < ActiveRecord::Base
  has_one :invoice_item
end

# Namedcope in Fee model

namedscope :uninvoiced, {
  :conditions => "fees.id NOT IN (SELECT fee_id FROM invoice_items)"
}

Authlogic login in rails functional tests

# Place this at the top of test/test_helper.rb
require "authlogic/test_case"

# Activating authlogic in before each test
def setup
  activate_authlogic
  UserSession.create(Factory(:teacher))
end

String value not displayed in input text field in a form

If you have the following,

<% form_tag '/index' do %>
  <% text_field_tag 'date', '2009-01-01' %>
  <% submit_tag 'Go' %>
<% end %>

You would think the textfield above would have "2009-01-01" string displayed. But it is not so. Need to specify "GET" method.

<% form_tag '/index', :method => :get do %>
...

Format string for titles

How to change "ClassTest" to "Class Tests"?

"ClassTest".titlecase.pluralize 

or 

"ClassTest".titleize.pluralize 

Specify form method when generating url route for edit form

Scratch head moment when I didn't specify ":method => :put" for edit form coz the form keeps leading me to "create" action.

<% form_for @class_test, :url => class_test_path(@class_test) do |f| -%>
  <%= render :partial => f %>
  <%= f.submit "Save" %>
<% end -%>

This was resolved after specifying the "put" method.

<% form_for @class_test, :url => class_test_path(@class_test), :html => {:method => :put} do |f| -%>
  <%= render :partial => f %>
  <%= f.submit "Save" %>
<% end -%>

Error using validation hooks with before_save callback

# This will throw "Schedule can't be blank" error as any changes made in before_save callback somehow gets lost
class Assessment < ActiveRecord
  validates_presence_of :schedule
  
  attr_accessor :date, :time
  before_save :set_schedule_from_date_and_time

  private

  def set_schedule_from_date_and_time
    if self.date && self.time
      self.schedule = Time.parse("#{date} #{time}")
    end
  end

# The trick is to use before_validation
  before_validation :set_schedule_from_date_and_time

Be careful with button_to in RESTful routes

# This will be default use POST method which in this context be sent as a create resource
<% form_for @course do |f| %>
...
<% end %>
<%= button_to 'Cancel', courses_path %>

# Specify GET method explicitly so it will call index resource instead
<%= button_to 'Cancel', courses_path, :method => :get %>

Problem with nested attributes for has one relation in form view

Scenario:

# app/models/teacher.rb
has_one :profile
accepts_nested_attributes_for :profile

# app/controllers/teachers_controller.rb
def new
  @teacher = Teacher.new
  @teacher.profile = Profile.new
end

If the following view give you error.

# app/views/teachers/_form.html.erb
<% form.fields_for :profile do |profile_form| %>
  ...
<% end %>

# Error in console
      You have a nil object when you didn't expect it!
      You might have expected an instance of ActiveRecord::Base.
      The error occurred while evaluating nil.new_record? (ActionView::TemplateError)
      On line #1 of app/views/teachers/_form.erb
      
          1: <% form.fields_for :profile do |profile_form| %>

Then it means you don't have any fields for parent object

<%= form.text_field :login %>
<% form.fields_for :profile do |profile_form| %>
  ...
<% end %>

Do not use Ruby's Enumerable find() method in Rails

According to ruby doc.

find	enumObj.find {| obj | block } -> anObject or nil
	Synonym for Enumerable#detect .

However if you ever try to use Enumerable#find in Rails, you'll get a "cannot find object without object id" error.

Better to use Enumerable#detect

The problem with using Rail's try() method

@jasonong             Try not to use Rail's try() method; makes debugging
                       difficult coz error not thrown.