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For those of you who wanted to use thoughtbot’s paperclip plugin to manage image uploads but were having trouble watermarking said images, behold!
Dynamically set a domain for a Rails asset host
I’ve been wanting to implement an asset host for my Rails app, looking over the API I saw that Rails’ asset_host only supported a single domain. I’m running multiple domains off one Rails app, so this would have been a problem. After a little research, I came up with a solution that would work for me.
I run this as a before_filter in my Application Controller.
# for my use, @site.domain returns the user's current # domain. you should change this to whatever method # you use to get the domain class ApplicationController < ActionController::Base before_filter :find_asset_host private def find_asset_host ActionController::Base.asset_host = Proc.new { |source| asset_hosts = %w{icarus zeus aphrodite etc etc} # disable asset host for development if is_development? "" else "http://#{asset_hosts[rand(4)]}.#{@site.domain}" end } end end
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Simple non-model check box properties
Need to pass a property that isn’t associated with a model? I did. It took me a few minutes, but the solution is pretty easy.
Instead of passing the instance variable your form is using, try this.
<% form_for [:admin, @post]} do |f| %> <%= f.error_messages %> <p> <%= f.label :title %> <%= f.text_field :title %> </p> <p> <%= label(:skip_queue, "Skip queue") %> <%= check_box("overrides", "skip_queue") %> </p> <p> <%= f.submit "Submit" %> </p> <% end %>
You’d access the property of the check box like so:
# log Processing Admin::PostsController#create (for 127.0.0.1 at 2009-03-06 03:03:01) [POST] Parameters: {"commit"=>"Update", "post"=>{"title"=>"Title", "overrides"=>{"skip_queue"=>"1"}} # access the property params[:overrides][:skip_queue]
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Paperclip deletes images with empty file fields update with rails 2.3
Bahhh! When you update a model that contains an empty file field in Rails 2.3 the attachment is deleted. It looks like empty file fields get passed as nil and then Paperclip gets angry.
Processing Admin::PostsController#update (for 127.0.0.1 at 2009-03-05 01:21:08) [PUT] Parameters: {"commit"=>"Update", "post"=>{"title"=>"Post Title", "image"=>nil}, "id"=>"124"}
There are two quick monkey patches that I’ve been using, the first, was splitting off attachments to their own method (edit_attachment)…but this quickly became a nuisance. A quicker work around is to remove the attachment field, in this case “image”, from the parameters.
# PUT /posts/1 # PUT /posts/1.xml def update @post = Post.find(params[:id]) # delete the offending parameter params[:post].delete(:image) if params[:post][:image].nil? respond_to do |format| if @post.update_attributes(params[:post]) flash[:notice] = 'Post was successfully updated.' format.html { redirect_to(admin_post_url(@post)) } else format.html { render :action => "edit" } end end end
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Watermark your images in Rails
I’ve been working on a project that requires me to watermark all my images. Here’s a script I put together using rmagick. I plan on releasing a skeleton application that will accept uploaded files and watermark them.
Ideally, I’d like to use paperclip to handle uploading, and write a processor subclass to handle watermarking…unfortunately I’m running into some issues. If anybody wants to lend a hand, I have the public repository up at: http://github.com/ng/paperclip-watermarking-app/tree
require 'RMagick' # load source and watermark images src = Magick::ImageList.new("source-image.jpg").first watermark = Magick::Image.read("watermark-image.png").first # create a new, blank image with a height that is the sum of # the source and watermark dst = Image.new(src.columns, src.rows+watermark.rows) { self.background_color = 'white' } # place the source image on the blank image result = dst.composite(src, Magick::NorthGravity, Magick::OverCompositeOp) # place the watermark over the previous transformation result = result.composite(watermark, Magick::SouthEastGravity, Magick::OverCompositeOp) # write it out result.write('watermarked-image.jpg')
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Paperclip not saving your images?
I’ve had a few guys email me asking if I had any idea why Paperclip wasn’t saving their uploaded images. Here’s a form one of them sent me:
<% form_for(@post) do |f| %> <%= f.error_messages %> <%= f.label :title %> <%= f.text_field :title %> <%= f.label :description %> <%= f.text_area :description %> <%= f.file_field :image %> <%= f.submit "Update" %> <% end %>
Notice anything different on this form?
<% form_for(@post, :html => { :multipart => true }) do |f| %> <%= f.error_messages %> <%= f.label :title %> <%= f.text_field :title %> <%= f.label :description %> <%= f.text_area :description %> <%= f.file_field :image %> <%= f.submit "Update" %> <% end %>
Simple mistake, but I’ve done it a few times in the early AM and wondered WTF was going on!
:html => { :multipart => true
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Check if a file exists in Rails
Recently I was porting a legacy PHP application to Rails. One of the primary tasks was to resize a bunch of images. Below you can see what one of the database rows looks like.
mysql> SELECT id, filename FROM old_posts +----+---------------------------------------+ | id | filename | +----+---------------------------------------+ | 1 | unxplained-photo-1225258423-85706.jpg | +----+---------------------------------------+ 1 row in set (0.00 sec) mysql>
You’ll see that the name of the filename is stored in the database, the problem I encountered was that often times the actual file didn’t exist even though the record remained in the database.
Rails would get angry at me when I tried to resize an non-existent file. To account for this, I did the following:
if FileTest.exists?(filename) # some code here to # resize the image end
For more information on this handy ruby module pop into the docs.
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Rails’ symbols: don’t create them dynamically!
Symbols are great, we use them in hashes all the time…but did you know, symbols aren’t part of Rails’ garbage collection? When you create them, the memory the use has been allocated permanently! Why is this bad? So if we create a handful of symobls…no biggie, but what if we’re dynamically creating lots and lots of them? Major faux pas!
This was brought to my attention last night when I was trying to create a hash with some dynamic symbols. See below:
## here is some data >> hardware = Hardware.find(:all, :limit => 2) => [#<Hardware id: 1, name: "Bolts", description: "Lorem ipsum dolor sit amet, consectetur adipisicing...", photo_front_file_name: "144_replica_wheels_Closeout_30_percent_off_prices_l...", photo_front_content_type: "image/jpeg", photo_front_file_size: 80842, photo_angle_file_name: nil, photo_angle_content_type: nil, photo_angle_file_size: nil, created_at: "2009-02-19 11:04:48", updated_at: "2009-02-20 20:29:46">, #<Hardware id: 2, name: "Nuts", description: "Lorem ipsum dolor sit amet, consectetur adipisicing...", photo_front_file_name: nil, photo_front_content_type: nil, photo_front_file_size: nil, photo_angle_file_name: nil, photo_angle_content_type: nil, photo_angle_file_size: nil, created_at: "2009-02-19 11:04:48", updated_at: "2009-02-20 07:18:32">] >> y hardware.first --- !ruby/object:Hardware attributes: name: Bolts updated_at: 2009-02-20 20:29:46 photo_angle_file_size: photo_front_file_name: 144_replica_wheels_Closeout_30_percent_off_prices_listed_.jpg photo_front_file_size: "80842" id: "1" description: Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. photo_angle_content_type: photo_front_content_type: image/jpeg created_at: 2009-02-19 11:04:48 photo_angle_file_name: attributes_cache: {} => nil
## don't do this for hardware_item in hardware formatted[:#{hardware_item.name.downcase}] = hardware_item.description end >> formatted[:bolts] => "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum." ## this is better for hardware_item in hardware formatted[hardware_item.name.downcase] = hardware_item.description end >> formatted['bolts'] => "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
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rake db:migrate for production databases
After I updated one of my applications that I’ve been working on, I kept running into an internal server error. I looked at the logs and for some reason none of my SQL queries were working.
Looks like I ran “rake db:migrate” and migrated the development database…not the production one. I scratched my head trying to remember the command. Here it is!”
rake db:migrate RAILS_ENV=”production”
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All Rails crash course tutorials are available on GitHub!
ZIP files are silly 
I’ve created a GitHub repository for all the tutorials to date and plan on using GitHub to version control all future applications. I will be editing the posts and removing any old download links shortly.
The repository is located at:
http://github.com/ng/crashcourse/tree/master
Want to check out the code? Run this in terminal:
git clone git://github.com/ng/crashcourse.git
Don’t have git installed? If you’re on OSX it’s simple!
http://code.google.com/p/git-osx-installer/
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