Formatting Numerical Input with Rails

Often, forms contain numerical fields for large numbers or monetary values.  In such situations, it’s very useful to format these inputs with javascript (adding commas, dollar signs and so on).  While the javascript is easy enough for this, rails does not like receiving commas or dollar signs in numerical fields.

Typically, one has two options to get rails to play nicely with this:

  1. To add a workaround in the model to scrub out unacceptable characters.
  2. To modify the submit button behavior to use javascript to scrub out those characters immediately prior to form submission.

Each of these strikes has always struck me as a bit cumbersome and intelligent.  Surely this operation is common enough that a plugin of sorts must exist to handle this.  …right?…….

Well I’m glad to tell you that after much searching, I’ve found a gem that does the trick.  It’s called autonumeric-rails and it can be found on github or on  The Gem uses the autoNumeric jquery plugin to format a numerical input with commas, dollar signs or whatever else you might want.

Here’s how it works:

On top of the jquery plugin it makes the input agreeable with rails by creating a pair of inputs for each field: one visible, one invisible.  The visible one is formatted using the standard jquery plugin, but the invisible one only contains the numerical value of the formatted visible field.  Therefore, upon submitting a form, only the invisible, unformatted field is submitted.

So how do i use it?

Implementing the gem is very simple and it can be used with most of the options from the autoNumeric jquery plugin.  Here’s how:

1.  Add the plugin to your Gemfile and “bundle install”

2.  Make sure that Jquery is “required” in your app and add autonumeric’s javascript file

//= require jquery
//= require autonumeric

3.  Add the necessary data attribute to your input field.

This is where the autoNumeric jquery plugin site comes in handy, which has an interactive interface for building the appropriate data attribute based on your needs.  Here are a couple examples.

4.  That’s it, enjoy!


…But wait is it?  Not quite, if you’re adding fields dynamically

Sometimes we want to add fields dynamically (once the page is already loaded).  Many rails developers use the favorite cocoon gem for such a situation.  The autoNumeric gem needs to be refreshed upon the addition of any fields in order for them to be formatted accordingly.  It should also be pointed out that we must use the GEM’S javascript calls and not those of the jQuery plugin.

So for some nested fields in cocoon (as shown below), we add the following javascript.

Now you’re actually done.  Happy coding!


Formatting Numerical Input with Rails

Polymorphic Associations The Smart Way: Using Global Ids

Global IDs have previously been a feature of rails with the help of a gem but as of Rails 4.2, it’s officially baked into the platform.  I just recently used the new addition to create polymorphic associations within an app and I have to say, it’s fantastic.  I did, however, find very little help out there for first-time users of this feature so here’s a few notes on how to do it.

What is a global id

Global Id is a library that produce Uniform Resource Identifiers (URIs) for any piece of data you’d like. They tend to look something like this:

Global IDs have previously been a feature of rails with the help of a gem but as of Rails 4.2, it’s officially baked into the platform.  I just recently used the new addition to create polymorphic associations within an app and I have to say, it’s fantastic.  I did, however, find very little help out there for first-time users of this feature so here’s a few notes on how to do it.

What is a global id

Global Id is a library that produce Uniform Resource Identifiers (URIs) for any activerecord object. They tend to look something like this:

So global IDs allow all of this information to be expressed in a single string very quickly.  With a couple methods in the model we can use this to create a polymorphic association.

Cool, so how do I make this happen?

Let’s pretend that we want to set up an association to indicate whether a Stockholder is a Person or a Company.

First, we need to generate our stockholder model

We will need two columns: entity_id and entity_type. Just like in the standard polymorphic association, the latter stores the model name, the former stores the id within that model.  We can generate both with a single line in our migration as follows:

class CreateStocholders < ActiveRecord::Migration
def change
create_table :optionees do |t| :grant_date
t.integer :shares_outstanding
t.belongs_to :option, index: true, foreign_key: true
t.references :entity, polymorphic: true, index: true
t.timestamps null: false

Next, we set up our models to indicate a polymorphic relationship

Company Model:
class Company < ActiveRecord::Base
has_many :stockholders, as: :entity

Person Model:
class Person < ActiveRecord::Base
has_many :stockholders, as: :entity

Stockholder Model:
class Stocholder < ActiveRecord::Base
belongs_to :entity, polymorphic:true

In the above case, :entity is just catch-all field that represents people and companies. Of course, you can call yours whatever you’d like.

Now we can set up our form for the stockholder

I use simple_form but the principle is the same for other methods; adjust your syntax accordingly. Something like this.

<%= f.grouped_collection_select :entity_id, [Company, Person], :all, :model_name, :to_global_id, :email %>
<%= f.input :issue_date, label: false %>
<%= f.input :shares_issued, label: false %>

So obviously, the exciting part here is the grouped_collection_select which will render a nice select menu with both companies AND people in it.

To break it down:

  • This is a grouped collection for a client
  • Over the models Company and Person
  • It will use all of the records in each model
  • and group them according to their model_name.
  • It will use the global_id to get the values
  • and display the email of each in the menu

The above will give you a grouped selector similar to the one shown below (note I used Org instead of Company, but you get the idea).

But you might rightly ask: “Why did you use email addresses and not names?”  The tricky thing about these sorts of associations is that people have both a first name and a last name where companies just have a name.  In order to get names to render in such a situation, you will need to use a lambda, which I’ll go over at the end of the post.

Making Global Ids work with Polymorphic Associations

If you’ve been keeping track though you should see that we have created two key problems for integrating the global id with polymorphic associations:

  1. We need :entity_type as well as :entity_id
  2. :entity_id needs to be an integer, not a string as is a global id.

So, to rephrase the situation, we need to break the global id into two pieces:

  1. Its model name (a string)
  2. Its id for that model (an integer)

Fortunately we don’t need to do this manually, rails polymorphic associations will store the model name and id automatically if it knows which object to reference.  Therefore, we specify getter/setter methods to specify the object, using global ids.

So, editing the Stockholder model again:

class Stocholder < ActiveRecord::Base
belongs_to :entity, polymorphic:true

def global_entity
self.entity.to_global_id if self.entity.present?

def global_entity=(entity)
self.entity=GlobalID::Locator.locate entity

Then change the grouped_collection_select to:
<%= f.grouped_collection_select :global_entity, [Company, Person], :all, :model_name, :to_global_id, :email %>
<%= f.input :issue_date, label: false %>
<%= f.input :shares_issued, label: false %>

Then just be sure to add :global_entity to your strong params and that’s it!


Using the lambda for names

Ok, often when doing polymorphic associations, one will use different pieces of information as keys for the two different models (after all, they’re not always going to have the same columns, right?)  In such a case, we use a lambda, making our select like this:
<%= f.grouped_collection_select :entity_id, [Company, Person], :all, :model_name, :to_global_id, lambda {|company_or_person_object| company_or_person_object.instance_of? Company? rescue company_or_person_object.fname + " " + company_or_person_object.lname rescue}, label:"Stockholder", class: "names"%>

As an explanation of lambdas is a bit beyond the scope of this tutorial, I’ll just leave you with the example above.  There is plenty of documentation available out there on the matter so if the lambda’s confusing, just google it up.

Anyway, that’s it; you’re done!


Polymorphic Associations The Smart Way: Using Global Ids

Adding a devise user or admin in a Heroku app

To add a devise user on a Heroku site we combine two commands

Command 1: With devise a person can enter the following into their rails console to create a user: => "", :password => 'password', :password_confirmation => 'password')

Command 2: To run commands in the Heroku terminal, simply go into local directory of the corresponding app and type heroku run [whatever you want to run]

So if we put those together we get the following, assuming that your user model is in fact called User:

    1. Change your directory to your app: cd ~/yourapp
    2. Enter into the rails console on Heroku with the following: heroku run rails c
    3. Run the create user code: => "", :password => 'password', :password_confirmation => 'password')
    4. Then finally

Finally, if you want to do this for a separate admin model, simply replace User in the instructions above with Admin (provided of course that’s what your separate admin model is called; if not adjust accordingly).

That’s it! You should be good to go!

Adding a devise user or admin in a Heroku app

Styling Fields Dynamically Added With Cocoon

I recently ran into a situation where I realized that the nice slick J-Query styling that I’d given to my select menus hadn’t carried over to my dynamically added fields.  This is because, my javascript ran $('select').customSelect(); when the page loaded but at no point after. I therefore needed to figure out how to trigger that function once a dynamic field was added.

After quite a bit of searching around (on the order of hours) and several dead ends, I finally learned that cocoon has many different actions that can be used with on() In my case, all I needed was the following:
$('#test').on("cocoon:after-insert", function(e, added_item){

And I was good to go.

Styling Fields Dynamically Added With Cocoon

A beginners look at RVM: Installs, Upgrades and the rest

One of the most confusing things about learning rails is in dealing with the Ruby Version Manager (RVM). Being a noob myself in the Ruby world, I wanted to give some clarification on stuff that I’d wondered at the outset regarding this tool.

RVM is basically a package manager (like apt for fellow linux users); it upgrades packages, downgrades them, allows you to switch out versions, etc. The big question on my mind was “why doesn’t ruby just use apt!?” Indeed, apt had served me well for php and it seemed to be a needless complication to use some other package manager for this language.  “Why was Ruby so special that it needed its own package manager!?”  I’m still not entirely sure of the rationale behind this, but my guess is that one of the things that makes Ruby so useful is its “Gems” (Rails is one of them), for which Ruby sort of acts as a package manager in itself.  I figure this makes it much more important for users to have a more control over the versions of ruby that they’re using; either way RVM (and a few others like it) are the ways to manage ruby, so here are a few tips to make it work.

Note: These instructions might have an Ubuntu flavor to them here and there, because that’s what I use.  For the most part, they’re universal though.

To install RVM:
\curl -sSL | bash -s stable --ruby

To check the version of ruby:
ruby -v

How can I upgrade to the latest version of ruby!?
There is no way to just upgrade ruby to the latest (whatever it happens to be). RVM seems to be all about giving control to YOU; it’s not going to make the choice for you. Here’s how I go about it.
First, I update my list of known stable ruby versions
rvm get master
Then, I check that updated list with:
rvm list known
My output looked like this:

# MRI Rubies
[ruby-]1.8.7[-head] # security released on head
# for forks use: rvm install ruby-head- --url --branch 2.1

The real output was actually a lot longer as it gives you ALL the packages you can get with RVM but I cut it off (we’re not interested in JRuby or anything like that).  Anyway, I checked out the list and saw that 2.2.0 was the latest so I entered:
rvm install 2.2.0

Managing installed versions:
RVM also allows a user to have many “Rubies” installed (versions of ruby).  To see which ones are installed:
rvm list
Mine looks like this:

rvm rubies

ruby-1.9.2-p320 [ x86_64 ]
* ruby-1.9.3-p392 [ x86_64 ]
=> ruby-2.2.0 [ x86_64 ]

# => – current
# =* – current && default
# * – default

I’m using 2.2.0. If I wanted to use the version of 1.9.3 I have, I would type
rvm use ruby-1.9.3-p392
Also my default was 1.9.3. If I wanted to change the default to 2.2.0, I would enter
rvm --default use 2.2.0

Upgrading RVM:
Every month or so it’s good to upgrade your rvm. To do so:
rvm get stable

A beginners look at RVM: Installs, Upgrades and the rest

Controller Cheat Sheet

Common in index method

Get all posts and save them to @post, ordered by when they were creating in descending order:

@post = Post.all.order("created_at DESC")

Get all posts by a particular user and save them to @post, ordered by when they were creating in descending order:
@post = current_user.posts("created_at DESC")

Common in new method

Create a new post for the current user when that user has_many posts:

@post =

Create a new post for the current user when that user only has_one post:

@post = current_user.build_post

To authorize which users can access what

See my post here.

Controller Cheat Sheet

Rolling your own basic user authorizations with devise

There seems to be very little written about this in the Rails literature out there, so I thought I’d make a contribution.  There’s very much posted about using authorization management gems like CanCan (which is well and good) but for those of us creating a small basic app, such gems are overkill.  It’s also worth using a filter just to get an understanding of what’s going on if you’re new to rails (like me!)


To create a stupid-simple authorization system that makes sure that only admins and the owner of a post can edit that post.


  1. You are using the devise gem and have set it up
  2. You have created an Admin model (Option 1 in the Devise Wiki)


(It’s really short)

To only allow admins and users that own the given post edit authorization, put the following in your post controller:

before_filter :require_permission, only: [:edit, :update, :destroy]

def require_permission
if user_signed_in?
if current_user != Post.find(params[:id]).user
if !admin_signed_in?
redirect_to :root, notice: "Access Denied."
if !admin_signed_in?

(Do make your indentation better than the code above; I’m up against wordpress’s auto-correct and don’t feel like fighting with it)

Anyway, that’s it!

The explanation

So why? Let’s start with the top

  1.  We’re adding a method, called require_permission which we are defining below to the methods edit, update and destroy.  Meaning any users engaging these methods must fit the requirements outlined in require_permission
  2. Next we define require_permission and say that if the current user is NOT the user on file for the given post… proceed.
  3. Then we check if the session user is an admin or, more accurately, if the user is NOT the admin (note the exclamation point).  Because user and admin are two different models, devise has defined two different sets of very similar methods when referring to either one.  Check them out here.  It helps clarify things.
  4. Finally we add the redirect to the homepage with an ominous “ACCESS DENIED” message at the top.

So to recap, if the user is not the owner of the post AND not signed into the admin model, they get booted back to the homepage.  Otherwise, they can do whatever they want to the post.



Rolling your own basic user authorizations with devise

Managing Administrator accounts with Devise

I’ve been using the Devise gem for a couple apps in my recent exploration of Ruby on Rails.  It works pretty well and has a lot of great features but the documentation on how to best go about setting up administrators on it is a bit vague.  I would write up some notes on how to do it but  I’d basically be plagiarizing another post on the matter which really cleared things up for me.  Check it out:

Managing Administrator accounts with Devise

Setting Up Mailer Using Devise For Forgot Password

Really cleared up my confusion about sending email in both development and production environments.

Ruby on Rails Help

In this tutorial I will show you how to set up the mailer for the forgot password feature in Devise. In the tutorial I will be setting up a Gmail account and I will show you how its done using local environment variables. I will also be using Heroku and Foreman to set up environment variables.

I am using Rails 4 and Devise 3 for this tutorial.

Seting Up Development Environment

First we will set up the development mailer for use on your local machine. In “config/environments/development.rb” you should already have included

config.action_mailer.default_url_options = { :host => 'localhost:3000' }

when you installed devise.

Next you should turn on the option to raise an exception if there is an error when sending an email. You can do this by including

config.action_mailer.raise_delivery_errors = true

in the same file. Next we will add the email delivery method. You should leave the values as…

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Setting Up Mailer Using Devise For Forgot Password