has-and-belongs-to-many

问题 I have problem with updating (better updating not recreating) extra field in HABTM join table. I searched google and other sources, but struggled for 4 days now. I have models: class Tutorial extends AppModel { var $hasAndBelongsToMany = array( 'TutorialCategory' => array( 'with' => 'TutorialCategoriesTutorial', 'order' => 'TutorialCategoriesTutorial.order_by ASC', 'unique' => true, ); } class TutorialCategory extends AppModel { var $hasAndBelongsToMany = array( 'Tutorial' => array( 'with' =>

问题 Say, we have a "Person" and "Favorite" models. "Favorite" is what this person likes: "music", "video", "sport", "internet", "traveling" etc. "Person" HABTM "Favorites", and "Favorite" HABTM "Persons" I need to find a Person, that has ALL listed "Favorites. For example, find a person, that likes "music", "traveling" and "sport". How it can be done, using ActiveRecord.find method ? 回答1: @people = Person.find(:all, :joins => :favourites, :select => "person.*, count(favourites) favourite_count",

问题 I have two rails active record classes, School and Instructor linked by a has_and_belongs_to_many relationship. I need to query my instructors_controller for instructors for a particular school and return an xml format response. Therefore, in the index method I have this code fragment: school = School.find(params[:school_id]) @instructors = school.instructors and later: respond_to do |format| format.html # index.html.erb format.xml { render :xml => @instructors } format.json { render :json =>

问题 I have a HABTM relationship between Users and Locations. Both Models have the appropriate $hasAndBelongsToMany variable set. When I managing User Locations, I want to delete the association between the User and Location, but not the Location. Clearly this Location could belong to other users. I would expect the following code to delete just the join table record provided the HABTM associations, but it deleted both records. $this->Weather->deleteAll(array('Weather.id' => $this->data['weather

问题 I have two models with a HABTM relationship - User and Role. user - has_and_belongs_to_many :roles role - belongs_to :user I want to add a uniqueness constraint in the join (users_roles table) that says the user_id and role_id must be unique. In Rails, would look like: validates_uniqueness_of :user, :scope => [:role] Of course, in Rails, we don't usually have a model to represent the join relationship in a HABTM association. So my question is where is the best place to add the constraint? 回答1

问题 I'm quite new to this and I'm using cancan + devise for my user auth. However I'm not really sure what it means to set up a typical users HABTM roles relationship nor do I really understand what a HABTM relationship is. Can anyone explain it really well or point me to a good tutorial or example? 回答1: HABTM means has and belongs to many. You basically need a table as a middle man to track multiple id's (called a through table). When referenced as a typical users HABTM roles relationship, they

问题 Mongoid ships with .push on a habtm, which sets a habtm relationship in both directions. Although delete will #delete an associated record, there's no documented way to delete only a relationship that I have seen. Is there a better way of doing this? Is there a better way of ensuring uniqueness? has_and_belongs_to_many :following, {class_name: 'User', inverse_of: :followers, inverse_class_name: 'User'} has_and_belongs_to_many :followers, {class_name: 'User', inverse_of: :following, inverse

问题 I have setup this HABTM relationship in the past and its worked before....Now it isnt and I'm at my wits end trying to figure out whats wrong. I've looking through the rails guides all day and cant seem to figure out what I'm doing wrong, so help would really be appreciated. I have 2 models connected through a join model and I'm trying to find records based an attribute of the associated model. Event.rb has_and_belongs_to_many :interests Interest.rb has_and_belongs_to_many :events and a join

问题 Spent all day on Google, but can't find an answer. :\ I have a HABTM relationship between Users and Core_Values. class CoreValue < ActiveRecord::Base has_and_belongs_to_many :users class User < ActiveRecord::Base has_and_belongs_to_many :core_values In my controller, I need to do two separate things: If a CoreValue does not exist, create a new one and associate it with a given user id, and Assuming I know a particular CoreValue does exist already, create the association without creating any

问题 I am trying to use formtastic to make a form where I can enter an :opposition choose a :venue and a :team and then be presented with a list of players that I am able to check off to select them for the I have got the form set up so it renders correctly however when submitted it does not save any information and just reloads the page. My code is at my github here: https://github.com/jpknegtel/st_francis models This concerns the following models: player has_many :player_fixtures has_many