#382 Tagging

gem 'acts-as-taggable-on'

rails g acts_as_taggable_on:migration
rake db:migrate

attr_accessible :content, :name, :tag_list
acts_as_taggable

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

def index
  if params[:tag]
    @articles = Article.tagged_with(params[:tag])
  else
    @articles = Article.all
  end
end

<div class="field">
  <%= f.label :tag_list, "Tags (separated by commas)" %><br />
  <%= f.text_field :tag_list %>
</div>

<div id="tag_cloud">
  <% tag_cloud Article.tag_counts, %w[s m l] do |tag, css_class| %>
    <%= link_to tag.name, tag_path(tag.name), class: css_class %>
  <% end %>
</div>
...
Tags: <%= raw article.tag_list.map { |t| link_to t, tag_path(t) }.join(', ') %>

#tag_cloud {
  width: 400px;
  line-height: 1.6em;
  .s { font-size: 0.8em; }
  .m { font-size: 1.2em; }
  .l { font-size: 1.8em; }
}

rake db:rollback
rails d acts_as_taggable_on:migration
rails g model tag name
rails g model tagging tag:belongs_to article:belongs_to
rake db:migrate

has_many :taggings
has_many :articles, through: :taggings

attr_accessible :content, :name, :tag_list
has_many :taggings
has_many :tags, through: :taggings

def self.tagged_with(name)
  Tag.find_by_name!(name).articles
end

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

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

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

Tags: <%= raw article.tags.map(&:name).map { |t| link_to t, tag_path(t) }.join(', ') %>

def tag_cloud(tags, classes)
  max = tags.sort_by(&:count).last
  tags.each do |tag|
    index = tag.count.to_f / max.count * (classes.size - 1)
    yield(tag, classes[index.round])
  end
end