#382 Tagging

Do we have XSS vulnerability because of displaying 'raw tags.map'? Hacker could inject some sort of malicious code in a tag name so it would be sent to user without escaping.

Thanks Ryan. I've been working on a some simple tagging with the native Postgres string-array type this week, it seems to work very well although I don't have any comparative data on performance yet.

https://github.com/dockyard/postgres_ext was a huge help for getting started with it.

Shouldn't the assignment of self.tags in the method tag_names= be moved to an after_save callback method? What if the validations on a newly created article fail? The tags would still be created without proper referencing.

Assuming that a tag should only be created once (unique constraint on name) I'd rather use:

self.tags = names.split(",").map do |n|
  Tag.find_or_create_by_name(n.strip)
end

instead of

self.tags = names.split(",").map do |n|
  Tag.where(name: n.strip).first_or_create!
end

For better performance one should also consider a counter cache on the belongs_to :tags in the taggings model. This would avoid the join when calculating the tag counts in:

def self.tag_counts
  Tag.select("tags.*, count(taggings.tag_id) as count").
    joins(:taggings).group("taggings.tag_id")
end

I implemented my own tagging system similar to the code you wrote a while back, but I noticed that it did not scale well. If you only have a few tags it works fine, but if you have hundreds of thousands or millions and similar numbers of articles then performance degrades substantially. I ended up having to do quite a bit of caching to get acceptable performance, especially for the tag cloud.

I did not use, or know about, the acts_as_taggable_on gem at the time. Does anybody know how well it scales? If not I will definitely be running some performance tests on it this week.

Such an awesome episode. Though to get this example to work, I had to adjust the syntax from line 2 of your routes.rb example from:

puts "get 'tags/:tag', to: 'articles#index', as: :tag"

to

puts "get 'tags/:tag' => 'articles#index', :as => :tag"

You probably want to replace

max = tags.sort_by(&:count).last

with

max = tags.max_by(&:count)

There's no need to sort the array only to pick the largest element.

article.tags.map(&:name).map { |t| link_to t, tag_path(t) }.join(', ')

should really be

article.tags.map { |t| link_to t.name, tag_path(t.name) }.join(', ')

The original code will produce unnecessary iterations that might start to affect performance once the number of tags increases. In general: Keep iterations to a minimum – in my experience, it's the number one performance problem of most Rails apps.

What if I want to query for articles that belong to multiple tags?

I tried this method:

Article.joins(:tags).where(:tags => { :name => ["foo", "bar"] } )

but this returns me every post that has either tag foo, or bar or both.

How do I search only for posts that have both foo and bar at the same time?

To complete the full circle, it would be great to see how to use tags with http://aehlke.github.com/tag-it/

There is only one thing that the gem covers in the example and the solution made from scratch doesn't cover: the relation for the tagging to belong to a user (act_as_tagger in the user model). How do you think this might be done, as most user authentication solutions (like Devise, Authlogic or Sorcery) doesn't provide the current_user helper in the ActiveRecord layer.

I haven't touched RoR in a month and getting rusty, took a small break came back to computer and it hit me, the problem was with a haml conversion from html:

WRONG WAY

#tag_cloud
  = tag_cloud Post.tag_counts, %w[css1 css2 css3 css4] do |tag, css_class|
    = link_to tag.name, tag_path(tag.name), class: css_class

RIGHT WAY

#tag_cloud
  - tag_cloud Post.tag_counts, %w[css1 css2 css3 css4] do |tag, css_class|
    = link_to tag.name, tag_path(tag.name), class: css_class

Can delete my questions to clean up this railscast =)

Any ideas how to overwrite the to_param method? Overwriting it in /app/models/tag.rb just doesn't work in urls, though it works in console when invokung Tag.first.to_param

What i mean is instead of urls like /tags/foo%20bar i would like to have urls like /tags/foo-bar

the tag_cloud from scratch isn't working here. Is it may be because I'm using postgresql as a database?

Hello! Thanks for gem. But I have problem: on editing model with tags, I have empty tags field. I tried both ways of realising but also empty.

<%= form_for(@post) do |f| %>
...
    <div class="field">
      <%= f.label :tag_list, "Tags (separated by commas)" %><br />
      <%= f.text_field :tag_list %>
    </div>
...
<% end %>

I tried to print simple @post.tag_list, an it is not empty but in form it is empty( Need help.

Awesome! With the help of this and http://railscasts.com/episodes/17-habtm-checkboxes-revised I was able to integrate this to work the way I wanted. Thanks Ryan.

Was noticing that this was not doing anything to standardize the capitalizations so therefore tagname and Tagname are two different things in this implementation, in order to fix this I simply used a before_save to titleize the names with this:

before_save :titleize

def titleize
  self.name = self.name.titleize
end

Pretty simple but assigning of the name threw me for a loop for a minute. Great cast!

Here are the necessary model methods for any DataMapper users:

has n, :taggings
has n, :tags, :through => :taggings

def self.tagged_with(name)
  Tag.all(name: name).articles
end

def tag_list
  tags.map(&:name).join(", ")
end

def self.tag_counts
  DataMapper.repository.adapter.select('select tags.*, t.count from tags inner join (select taggings.tag_id, count(taggings.tag_id) as count from taggings group by taggings.tag_id) t where tags.id = t.tag_id')
end

def tag_list=(names)
  self.tags = names.split(',').map do |n|
    Tag.first_or_create(name: n.strip)
  end
end

Hope that helps.

When trying to tag an article, lets say "chemistry, sept 20/2012" as in want to organize all the articles posted on a certain date.
How do you rewrite the routes.rb:
get 'tags/:tag', to: 'articles#index', as: :tag
in order to access tag names that embed "/" forward slash?!
I get this error when I try to access sept 20/2012:
No route matches [GET] "/tags/sept%2020/2012"

Hello. I have a problem. This app use sqlite3, but i need postgresql. I edit my Gemfile and database.yml. My app work in rails server, but on heroku doesn't. May be it's needs to edit something other. Write me please, what i needs to edit to use postgersql.

Hello there,

This episode is great and helpful,but what if I need additional fields for storing like tag description? Any idea?

What would it look like to add two tags to an existing or new article at the rails command line?
Thanks!