Mai 2009 Archives

Mysql has a special 'INSERT ... ON DUPLICATE KEY UPDATE' statement which can be used for some models like e.g. ratings. Instead of something similar to this:
if m = Model.find(...) m.update else m = Model.new(params) m.save! end
You can just do this: m = Model.new(params) m.save!

when the row already exists in the database (detected by a unique-constraint violation) the values of that row are updated and saved, otherwise the new row is created.

My current solution is this:
module InsertOrUpdate def create create_or_update_impl end def update create_or_update_impl end def create_or_update_impl attrs = attributes_with_quotes(false,false) unless attrs.empty? self.id = connection.insert <<-end_sql ,"#{self.class.name} Create or update" INSERT INTO #{self.class.quoted_table_name} (#{quoted_column_names(attrs).join(', ')}) VALUES(#{attrs.values.join(', ')}) ON DUPLICATE KEY UPDATE #{update_values_partial}, id = LAST_INSERT_ID(id) end_sql end @new_record = false self.id end # returns "attr1 = 'value1', attr2 = 'value2', ..." def update_values_partial attrs = attributes_with_quotes(false,false) attrs.collect{|attr,value| "#{attr}=#{value}" }.join(",") end module ClassMethods def insert_or_update include InsertOrUpdate end end end ActiveRecord::Base.extend(InsertOrUpdate::ClassMethods)
You use it like this: class Model < ActiveRecord::Base insert_or_update # this includes the module and overwrites the default create and update methods end
Warning: You need mysql 5.1 so that LAST_INSERT_ID(id) works. (Mysql bug)

In my rails application i often have this kind of code in my erb/haml files: button_to "CommentRating.actions.create",comment_ratings_path, :rating => CommentRating::Good, :comment_id => @comment.id button_to "Comment.actions.destroy", @comment, :method => :delete
There is some repetition in it. Why not infer the i18n-key from the action? My approach: button_to CommentRating.actions.create(:rating => CommentRating::Good, :comment_id => @comment.id) button_to @comment.actions.destroy, :method => :delete # or even better button_to CommentRating.actions.create(:rating => :good, :comment => @comment) button_to @comment.actions.destroy # method is inferred from action
The parameters should also be passed to the i18n key. So for the first button_to call the translation method is invoked with: _('CommentRating.actions.create',:rating => :good, :comment => @comment)
Some of these ideas are relatively easy to implement:
Requirements:

• Each model needs an class-method called 'actions'
• Each model needs an instance-method called 'actions'
• The actions-methods return an proxy (ActionProxy) that records the method name that is invoked on it (method name = action name)
• the proxy returns an information object (ActionInformation) that contains:
  1. the instance or the class of the model
  2. the action name
  3. the parameters
• the ActionInformation has methods that infer the i18n key as well as the url

# Comment.actions.new #=> determines url, i18n key and parameters # @comment.actions.destroy #=> determines url with id of @comment # CommentRating.actions.create(:rating => :good, :comment_id => @comment.id) module ActionExtension # An instance of this class is returned when Comment.actions.new is called class ActionInformation attr_reader :instance, :klass, :action, :params def initialize(options) @instance, @klass, @params, @action = options[:instance],options[:class],options[:params], options[:action] @klass = @instance.class if @instance end def i18n_key # TODO parameter handling ["#{klass.model_name}.actions.#{action}",params.first] end def controller klass.model_name.plural end def url url = {:controller => controller, :action => action} url.merge!(:id => @instance.to_param) if @instance # TODO parameter handling: current solution: merge hash into url; better: add hidden fields url.merge!(@params.first) if @params.any? and @params.first.is_a? Hash url end end # proxy = @comment.actions #=> InstanceActionProxy(@comment) # proxy.rate(:good) #=> InstanceActionProxy(@comment).method_missing class ActionsProxy def initialize(options) raise unless options.is_a? Hash @options = options.dup end def method_missing(meth,*params) ActionInformation.new(@options.merge!(:action => meth, :params => params)) end end # called when included in ActiveRecord::Base def self.included(base) base.class_eval do # called when Model inherits from ActiveRecord::Base def self.inherited(child) #child.extend(ActionDefinition) child.class_eval do def actions ActionsProxy.new(:instance => self) end def self.actions ActionsProxy.new(:class => self) end end super end end end end ActiveRecord::Base.send(:include,ActionExtension)
Now this can be used like this: info = Comment.actions.create(:param => 1) info.i18n_key #=> ['Comment.actions.create',{:param => 1}] info.url #=> {:controller => 'comments', :action => 'create', :param => 1} info = @comment.actions.destroy info.i18n_key #=> ['Comment.actions.destroy'] info.url #=> {:controller => 'comments', :action => 'destroy', :id => @comment.to_param}
Improvements to work on:

• infer method (:delete etc)
• dont merge the parameters into the url. make them accessible seperately so they can be extracted and posted via hidden fields inside a form.
• maybe redefine actions in the models to preprocess the parameters: define_action :rate => lambda{|*params| {:rating => params[1]} }

I'm using the haml plugin in my rails application. In haml you can output plaintext like this: %div plaintext here

Since i never output plaintext in my view because i use i18n i decided to modify haml: %div my.i18n.key.here

So instead of outputting plaintext, you supply a i18n-key and haml outputs the translated text that belongs to that key.

The modification is quick & dirty and just a few lines long:
Go to the haml precompiler.rb and find the render_tag method. There should be a 'switch action' switch. Add the following lines to the switch: switch action #[...] when '', nil if not value.blank? parse = true key, params = value.scan(/\A[^,]+|[^,].*\Z/) params = ',' + params unless params.blank? value = "_('#{key}'#{params})" end end #[...] end
This assumes that '_' is the method that is used for i18n. You can even append parameters: %div my.i18n.key.here, :param1 => 'value'
This invokes _('my.i18n.key.here',:param1 => 'value')