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Randy

How to create PDF’s and Images from your website in Rails

Rails

I am going to show you how to generate both a pdf and image from a single action in a controller using the awesome, wkhtmltopdf library. This also uses PDFKit and WebSnap gems available on GitHub. This example assumes the following:

  • wkhtmltopdf and wkhtmltoimage are already installed and accessible on in the PATH.
  • You have an html page setup to display the record.
  • You have created a pdf CSS file to help display the pdf, if you so choose.
# config/initializers/mime_types.rb
Mime::Type.register "application/pdf", :pdf
Mime::Type.register "image/png", :png

# app/controllers/items_controller.rb
def show
  @item = Item.find(params[:id])
  
  respond_to do |format|
    format.html { }
    format.pdf {
      html = render(:action => "show.html.erb")
      
      kit = PDFKit.new( html, :zoom => 0.75 )
      kit.stylesheets << File.join(RAILS_ROOT,
                                   "public",
                                   "stylesheets",
                                   "pdf.css")
      
      send_data kit.to_pdf, :filename => "item.pdf",
                            :type => "application/pdf",
                            :disposition => "inline"
    }
    format.png {
      html = render :action => "show.html.erb",
                    :layout => "application.html.erb"

      # I am nil’ing these options out because my version of wkhtmltoimage does
      # not support the scale options and I do not want to crop the image.
      snap = WebSnap.new(html, :format => "png",
                               :"scale-h" => nil,
                               :"scale-w" => nil,
                               :"crop-h" => nil,
                               :"crop-w" => nil,
                               :quality => 100,
                               :"crop-x" => nil,
                               :"crop-y" => nil)

      send_data snap.to_bytes, :filename => "item.png",
                               :type => "image/png",
                               :disposition => "inline"
    }
  end
end

Now you should be able to access three distinct views, each producing a different result

http://example.com/items/1 # => Generates an html page.
http://example.com/items/1.pdf # => Generates a pdf of the html page.
http://example.com/items/1.png # => Generates a png of the html page.

You could easily also add more image types by just created another block for each format, and changing the :format to whatever one you would like.

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Randy

Including methods and associations in a JSON Data set with Rails

Rails

I was poking around while working with creating an application specifically for web services. We decided to use JSON as the methods of transportation of data, but the problem came when I wanted to include custom methods, or associations in my data set. The solution was fairly simple, using the to_json method. Suppose you have the following classes:

class Client < ActiveRecord::Base
  has_many :employees
end

class Employee < ActiveRecord::Base
  belongs_to :client

  def full_name
    "#{first_name} #{last_name}"
  end
end

We want the controller to return a client with association employees and the full name in the database. Here is how we would go about doing that:

def show
  @client = Client.find(params[:id])

  respond_to do |format|
    format.json { render :json => @client.to_json(:include => { :employee => { :only => :email, :methods => [:full_name]}})}
  end
end

You will end up with the following data set:

{
  client: {
    name: "Some client",
    employee: {
      email: "test@test.com",
      full_name: "John Doe"
    }
  }
}

Forgive me if I messed up the json output…doing it from memory 🙂 There are of course way easier uses for this too, but I just decided to spit out a more complex one.

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Randy

ActiveRecord – Making :include and :select play nice!

Rails

So I have been using a nice plug-in that will allow me to using :select when using :include, and not have it pull the entire data set. You can add the plug-in to your app like this:

script/plugin install git://github.com/blythedunham/eload-select.git

Here are some ways to use the plug-in:

Employee.find :all,
  :select => "addresses.city, address.state, employees.*",
  :include => :address

Employee.find :first,
  :select => "now() as current_time, addresses.city, DATE(addresses.created_at) as addresses.created_at, employee.*",
  :include => :address

Employee.find :all,
  :select => "addresses.city, employees.name, employees.start_date",
  :include => :address

Examples taken from:

http://www.snowgiraffe.com/tech/329/eager-loading-select-plugin-when-select-plays-nice-with-include/

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Randy

Turn off Rails sessions by request type

Rails

Here is a solution to turn sessions off based on a request type. I added this to application.rb file:

session :off,
  :if => Proc.new { |req| ['xml', 'rss'].include?(req.params[:format]) }

You could ideally just add this to an individual controller, and add :only or :except to it as well, but I wanted to eliminate all of the controllers and actions.

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Randy

Easy True/False Select Tag with Rails

Rails

It’s been a while since my last post. I have been pretty busy with other things, but thats no excuse. Anyway, I came across a problem where I needed to create a select tag with just a true and false option in it and came up with the following quick and easy solution. (This would presumably work with more/different options as well): First, create a file in the config/initializers directory. This is where your global variables will go for use in the select tags. I called mine select_tag_globals.rb:

TRUE_FALSE = { 'True'=>true, 'False'=>false }

Make sure the values are set to whatever the fields data type is. In this case I want the labels to say True or False, and the value saved to the database will be true or false. Now all we have to do is use this in a select tag in a view like so:

<%= f.select :database_field, TRUE_FALSE %>

This should give you a normal select box with True and False labels. Yay rails!

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Randy

ActiveRecord and Transactions!

Rails

If you ever have to do multiple actions with activerecord, you should group it into a transaction like so:

Post.transaction do
  posts.each do |post|
    post = Post.new(:body=>'Whatever')
    post.save!
  end
end

This will rollback too if the save fails.

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Randy

Restful Authentication and Basic HTTP Auth

Rails

I had an application that was prompting a HTTP Authentication box in IE after using the restful authentication plugin. The way I fixed it was to replace the access_denied method in lib/authenticated_system.rb to:

def access_denied
  respond_to do |format|
    format.any do
      #format.html do
      store_location
      redirect_to new_session_path
    end
    #format.any do
      #  request_http_basic_authentication 'Web Password'
    #end
  end
end

Noticed I commented some lines out. This was so that if i ever need to revert, the code will still be there and I wont have to go looking for it. Hope this helps!

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Randy

Rails route helpers – route_url vs route_path

Rails

If you weren’t already aware of this, there IS a difference between using route_url and route_path. Here are what they return:

<%= posts_url %>  # => http://localhost:3000/posts
<%= posts_path %> # => /posts

As a general rule of thumb, you would want to use posts_url in your controllers, and posts_path in your views.

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Randy

href jumps to top of page

Rails

While this isn’t a ruby on rails specific issue, I do tend to do this a lot, and never thought twice about it, until it starts bugging the crap out of me. The issue is that you have a link that is used to do some type of javascript, instead of linking. So you add an onclick event, but you need something to link to. I usually put in a # sign:

Do Something

 
<%= link_to 'Do Something', '#', :onclick=>'dosomething()' %>

This is great, except that it jumps you to the top of the page. Very annoying. Here is the solution:

Do Something

 
<%= link_to 'Do Something', '#nogo', :onclick=>'dosomething()' %>

Notice I added “nogo” to my #. This will help prevent from jumping to the top of the page. You can of course use any text you want there.

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Randy

ActiveRecord conditions with association from hash

Rails

I’m sure you all know how to use the :conditions attribute when using ActiveRecord:

User.find(:all, :conditions=>['active = ?', true])

And you may even use associations this way:

User.find(
  :all,
  :include=>[:photos],
  :conditions=>['photos.removed = ? and users.active = ?', false, true]
)

But did you know that you can do this easier through hashes?

User.find(:all, :conditions=>{:active=>true})
User.find(
  :all,
  :include=>[:photos],
  :conditions=>{'photos.removed'=>false, 'users.active'=>true}
)

Nothing special there, but I thought it was pretty cool. One thing you have to remember when using associations, is to include that model.

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