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 https://get.rvm.io | 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 https://github.com/github/ruby.git --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 = current_user.posts.build

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: http://jonallured.com/2011/04/30/using-devise-for-admin-accounts.html

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