associations

问题 I have a class Agreement that has two belongs_to associations to a Member class - referenced as primary and secondary: class Agreement < ActiveRecord::Base belongs_to :primary, class_name: 'Member' belongs_to :secondary, class_name: 'Member' ... def self.by_member(member_attribute_hash) # returns any agreements that has a primary OR secondary member that matches any of the values # in the member_attribute_hash ... end end The Member class has no knowledge of the association with the Agreement

问题 Before anything else, thanks for read and sorry for my english. Entities: Morfologia namespace Content\Entity; /** * Morfologia * * @ORM\Entity * @ORM\Table(name="morfologia") * @Annotation\Name("morfologia") * @Annotation\Hydrator("Zend\Stdlib\Hydrator\ObjectProperty") */ class Morfologia { /** * @ORM\Id * @ORM\GeneratedValue(strategy="AUTO") * @ORM\Column(type="integer") * @Annotation\Type("Zend\Form\Element\Hidden") */ private $id; /** @ORM\Column(type="string") * @Annotation\Type("Zend

问题 I have two models, folder and files. A folder has many files. If I say folder.get('files') I get all the files associated with that folder ordered by id. I would like the array of files to be order by something other then the id; lets say createDate. If possible, I do not want to make a computed property that has a different name then files . Any help would greatly be appreciated? 回答1: As mentioned in my comment you need to create an computed property files in your controller, which contains

问题 I have a user model which has_one profile. The user model has a name attribute which is set when a user signs up. However, I want to let a user update that name attribute from the profile's edit view. How can I do this? 回答1: Nested attributes and the fields_for form helper are your friends. class Profile < ActiveRecord::Base belongs_to :user accepts_nested_attributes_for :user end That allows you to give nested user attributes to the profile: ruby-1.9.2-p0 > params = { :profile => { :some

问题 I need to create an UML Class Diagram and I am not sure if I've done it correctly. I will show you on example. So ClassA has an instance of ClassB and ClassA calls methods from ClassC which take as attributes variables from ClassA and ClassB. Should I connect also ClassC with ClassB? Does the association between ClassA and ClassB should be directed? The implementation of the code below: ClassB { constructor() { this.str1 = "Hello"; } } ClassA { constructor() { this.str2 = "World"; this.objB =

问题 Let's say I have the following relation: Reference(slide_id, group_id) where reference is the association of a slide and a group. One slide can be used in many references (with a different group): primary key is slide_id + group_id , which must be unique. I want to have all the references deleted when either of the pointed group or slide are deleted. Which I do by adding a cascade in the backref of the relationship: # definition of Reference model slide = db.relationship( Slide, backref=db

问题 Is it possible to order the results of school.classrooms by the teacher's name? I want to do this directly in the association, and not a separate call. class School < ActiveRecord::Base has_many :classrooms end class Classroom < ActiveRecord::Base belongs_to :school belongs_to :teacher end class Teacher < ActiveRecord::Base has_one :classroom end 回答1: This should work if you are using rails 3.x school.classrooms.includes(:teacher).order("teachers.name") 来源： https://stackoverflow.com/questions

问题 Following question also refers to discussion in following questions as well https://stackoverflow.com/search?page=2&tab=Relevance&q=one%20to%20many%20unidirectional%20java Best practise for adding a bidirectional relation in OO model I tried to implementing 8 association combinations formed by [Unidirectional/Bidirectional] X [(One/Many) to (One/Many)] in Java. I found two cases can not be implemented namely Unidirectional One to One and Unidirectional One to Many (e.g. Person->*Vehicle).

问题 I have the following models which basically refer to Lessons and Categories. Each lesson can have one category, and each category is embedded in a lesson. class Lesson include Mongoid::Document field :title, :type => String field :category, :type => String field :price, :type => Integer field :description, :type => String field :user_id, :type => String validates_presence_of :title validates_presence_of :category validates_presence_of :price validates_presence_of :user_id validates

问题 I have a Rails Movie app. With, obviously, a movie table. A movie has_many :comments, :dependent => :destroy and a comment belongs_to :movie . A comment also belongs_to :user so when a new User comments on a movie, that comment will display on their users#show page. If a User Comments on a Movie , the comment will display on their page. I can also go to localhost:3000/comments/:id to see that comment's show page Now my problem is this: If I then destroy or delete that movie with that comment,