Screencast: Include versus Joins

Download: Download(22.8 MB, 11:37) Alternativer Download für iPod & Apple TV(16.2 MB, 11:37)

Ressourcen:

• Hirb
• Gesamte Quellcode für diese Folge

Quellcode:

[ruby]

# script/console ActiveRecord::Base.logger = Logger.new(STDOUT) # to show logs c = Comment.all(:joins => :user, :conditions => { :users => { :admin => true } }) c.first.users c = Comment.all(:include => :user, :conditions => { :users => { :admin => true } }) c.first.users User.all(:joins => :comments, :select => “users.*, count(comments.id) as comments_count”, :group => “users.id”) g = Group.first Comment.all(:joins => {:user => :memberships}, :conditions => { :memberships => { :group_id => g.id } })

# models/comment.rb class Comment < ActiveRecord::Base belongs_to :user end

# models/user.rb class User < ActiveRecord::Base has_many :memberships has_many :groups, :through => :memberships has_many :comments end

# models/membership.rb class Membership < ActiveRecord::Base belongs_to :user belongs_to :group end

# models/group.rb class Group < ActiveRecord::Base has_many :memberships has_many :users, :through => :memberships def comments Comment.scoped(:joins => {:user => :memberships}, :conditions => { :memberships => { :group_id => id } }) end end

# comments_controller.rb def index @comments = Comment.all(:joins => :user, :conditions => { :users => { :admin => true } }, :order => “comments.created_at desc”) end

# users_controller.rb def index @users = User.all(:joins => :comments, :select => “users.*, count(comments.id) as comments_count”, :group => “users.id”) end [/ruby]

[ruby] <%= render @group.comments %>

<%= pluralize user.comments\_count, "comment" %> \[/ruby\]