1 files changed, 83 insertions, 0 deletions
diff --git a/actionpack/lib/action_view/record_identifier.rb b/actionpack/lib/action_view/record_identifier.rb
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+++ b/actionpack/lib/action_view/record_identifier.rb
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+require 'active_support/core_ext/module'
+require 'action_controller/model_naming'
+
+module ActionView
+  # The record identifier encapsulates a number of naming conventions for dealing with records, like Active Records or
+  # pretty much any other model type that has an id. These patterns are then used to try elevate the view actions to
+  # a higher logical level.
+  #
+  #   # routes
+  #   resources :posts
+  #
+  #   # view
+  #   <%= div_for(post) do %>    <div id="post_45" class="post">
+  #     <%= post.body %>           What a wonderful world!
+  #   <% end %>                  </div>
+  #
+  #   # controller
+  #   def update
+  #     post = Post.find(params[:id])
+  #     post.update_attributes(params[:post])
+  #
+  #     redirect_to(post) # Calls polymorphic_url(post) which in turn calls post_url(post)
+  #   end
+  #
+  # As the example above shows, you can stop caring to a large extent what the actual id of the post is.
+  # You just know that one is being assigned and that the subsequent calls in redirect_to expect that
+  # same naming convention and allows you to write less code if you follow it.
+  module RecordIdentifier
+    extend self
+
+    include ModelNaming
+
+    JOIN = '_'.freeze
+    NEW = 'new'.freeze
+
+    # The DOM class convention is to use the singular form of an object or class.
+    #
+    #   dom_class(post)   # => "post"
+    #   dom_class(Person) # => "person"
+    #
+    # If you need to address multiple instances of the same class in the same view, you can prefix the dom_class:
+    #
+    #   dom_class(post, :edit)   # => "edit_post"
+    #   dom_class(Person, :edit) # => "edit_person"
+    def dom_class(record_or_class, prefix = nil)
+      singular = model_name_from_record_or_class(record_or_class).param_key
+      prefix ? "#{prefix}#{JOIN}#{singular}" : singular
+    end
+
+    # The DOM id convention is to use the singular form of an object or class with the id following an underscore.
+    # If no id is found, prefix with "new_" instead.
+    #
+    #   dom_id(Post.find(45))       # => "post_45"
+    #   dom_id(Post.new)            # => "new_post"
+    #
+    # If you need to address multiple instances of the same class in the same view, you can prefix the dom_id:
+    #
+    #   dom_id(Post.find(45), :edit) # => "edit_post_45"
+    #   dom_id(Post.new, :custom)    # => "custom_post"
+    def dom_id(record, prefix = nil)
+      if record_id = record_key_for_dom_id(record)
+        "#{dom_class(record, prefix)}#{JOIN}#{record_id}"
+      else
+        dom_class(record, prefix || NEW)
+      end
+    end
+
+  protected
+
+    # Returns a string representation of the key attribute(s) that is suitable for use in an HTML DOM id.
+    # This can be overwritten to customize the default generated string representation if desired.
+    # If you need to read back a key from a dom_id in order to query for the underlying database record,
+    # you should write a helper like 'person_record_from_dom_id' that will extract the key either based
+    # on the default implementation (which just joins all key attributes with '_') or on your own
+    # overwritten version of the method. By default, this implementation passes the key string through a
+    # method that replaces all characters that are invalid inside DOM ids, with valid ones. You need to
+    # make sure yourself that your dom ids are valid, in case you overwrite this method.
+    def record_key_for_dom_id(record)
+      key = convert_to_model(record).to_key
+      key ? key.join('_') : key
+    end
+  end
+end