Simple, user-friendly cancel links for your Rails forms

The default Rails view generator includes back links on form-related view templates, so if users change their mind they can easily get out of the form and on to something else. However, these links are static. What do you do if you allow users to access the form from multiple views (say, an index and a show).

Here’s a simple but effective solution I came up with: Instead of passing a static URL, I pass the HTTP referrer environment variable as the location. That way users are taken back to the page from which they opened the form to begin with.

Here’s how it works. Most of the code resides in the application_helper.rb file:

  module ApplicationHelper
    include Rails.application.routes.url_helpers

    def cancel_link
      return link_to 'Cancel', request.env["HTTP_REFERER"], 
        :class => 'cancel', 
        :confirm => 'Are you sure? Any changes will be lost.'
    end
  end

You’ll need to include Rails.application.routes.url_helpers in order to access link_to from a helper method. Then you add the helper method itself, which does nothing more than return a cancel link. Mine uses an old-style :confirm message; you can spruce it up with some less obtrusive if you’d like.

If I need a cancel link in a view, I just add

  <%= cancel_link %>

The result: a flexible, reusable cancel option that’s much more user-friendly.

Counters for Partials

Sometimes I like to number rows using a counter when rendering lists of things:

<% @products.each_with_index do |product, i| %>
  <li class="product_<%= i %>"><%= product.name %></li>
<% end %>

They are handy for testing, among other things.

Of course, if the content of the block gets too big I’ll factor it out into a partial. The idiomatic Rails way of doing this is to factor the block contents out into a partial and then render it with the :collectionoption:

< %= render :partial => "product", :collection => @products %>

Which is very clean, except now where do we get our row counter? As it turns out, Rails provides one for us:

  <li class="product_<%= product_counter %>"><%= product.name %></li>

Note the use of product_counter. Rails takes the name of the partial and adds _counter to it when providing the built-in counter.

Copy a file from your system to EC2 Server with port and pem file

Here is command for Copying a file from your system to EC2 Server with port and pem file:

scp -P <PORT> -i xyz.pem  /home/user/file.txt  ec2-user@host:/home/ec2-user/

Below are the all available options that you can use based on your requirements:

scp [-12346BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file] [-l limit] [-o ssh_option] [-P port] [-S program] [[user@]host1:]file1 ... [[user@]host2:]file2

Irreversible Migrations in Ruby on Rails

In Rails 2 in migrations there were only 2 methods: up and down. They are called on running migrations up and down respectively with rake tasks rake db:migrate and rake db:rollback.

In Rails 2

def up
add_column :users, :active, :boolean User.update_all(active: true) end

def down remove_column :users, :active end

Rails 3 produced us great method change which allowed us to write there code which creates a table and drops the table automatically on rolling migration back. But unfortunately there was a problem – you didn’t have opportunity to say “don’t run this peace of code on down but run this only on up”. So the solution was just to use old syntax.