has-many | 易学教程

Rails has_many with alias name

阅读更多关于 Rails has_many with alias name

问题 In my User model I could have: has_many :tasks and in my Task model: belongs_to :user Then, supposing the foreign key 'user_id' was stored in the tasks table, I could use: @user.tasks My question is, how do I declare the has_many relationship such that I can refer to a User's Tasks as: @user.jobs ... or ... @user.foobars Thanks a heap. 回答1: Give this a shot: has_many :jobs, foreign_key: "user_id", class_name: "Task" Note, that :as is used for polymorphic associations. 回答2: You could also use

How to create NHibernate HasManyToMany relation

阅读更多关于 How to create NHibernate HasManyToMany relation

I know there are questions about HasManyToMany but this time I want to put couple fields into middle table like 'Description, CreationDate'. For my situation I don't want to bind two way. I have company, person and address tables. And every company or person may have more than 1 address. In this situation what should I do? How should I write the code of classes and mappings? Below you can see the tables: Radim Köhler In this case the answer is pretty simple. Do not use many-to-many. Use pairing object. Exactly for the reasons you've mentioned: Extend the pairing object with more properties:

Need data from rails join table, has_many :through

阅读更多关于 Need data from rails join table, has_many :through

问题 I have 3 tables - users, things, and follows. Users can follow things through the follows table, associating a user_id with a things_id . This would mean: class User has_many :things, :through => :follows end class Thing has_many :users, :through => :follows end class Follow belongs_to :users belongs_to :things end So I can retrieve thing.users with no problem. My issue is if in the follows table, I have a column named "relation", so I can set a follower as an "admin", I want to have access

Validate the number of has_many items in Ruby on Rails

阅读更多关于 Validate the number of has_many items in Ruby on Rails

Users can add tags to a snippet: class Snippet < ActiveRecord::Base # Relationships has_many :taggings has_many :tags, :through => :taggings belongs_to :closing_reason end I want to validate the number of tags: at least 1, at most 6. How am I about to do this? Thanks. Nikita Rybak You can always create a custom validation . Something like validate :validate_tags def validate_tags errors.add(:tags, "too much") if tags.size > 5 end sbonami A better solution has been provided by @SooDesuNe on this SO post validates :tags, length: { minimum: 1, maximum: 6 } asukiaaa I think you can validate with

Rails Model has_many with multiple foreign_keys

阅读更多关于 Rails Model has_many with multiple foreign_keys

Relatively new to rails and trying to model a very simple family "tree" with a single Person model that has a name, gender, father_id and mother_id (2 parents). Below is basically what I want to do, but obviously I can't repeat the :children in a has_many (the first gets overwritten). class Person < ActiveRecord::Base belongs_to :father, :class_name => 'Person' belongs_to :mother, :class_name => 'Person' has_many :children, :class_name => 'Person', :foreign_key => 'mother_id' has_many :children, :class_name => 'Person', :foreign_key => 'father_id' end Is there a simple way to use has_many with

Rails has_many :through Find by Extra Attributes in Join Model

阅读更多关于 Rails has_many :through Find by Extra Attributes in Join Model

New to both Ruby and Rails but I'm book educated by now (which apparently means nothing, haha). I've got two models, Event and User joined through a table EventUser class User < ActiveRecord::Base has_many :event_users has_many :events, :through => :event_users end class EventUser < ActiveRecord::Base belongs_to :event belongs_to :user #For clarity's sake, EventUser also has a boolean column "active", among others end class Event < ActiveRecord::Base has_many :event_users has_many :users, :through => :event_users end This project is a calendar, in which I have to keep track of people signing

How to create NHibernate HasManyToMany relation

阅读更多关于 How to create NHibernate HasManyToMany relation

问题 I know there are questions about HasManyToMany but this time I want to put couple fields into middle table like \'Description, CreationDate\'. For my situation I don\'t want to bind two way. I have company, person and address tables. And every company or person may have more than 1 address. In this situation what should I do? How should I write the code of classes and mappings? Below you can see the tables: 回答1: In this case the answer is pretty simple. Do not use many-to-many. Use pairing

Validate the number of has_many items in Ruby on Rails

阅读更多关于 Validate the number of has_many items in Ruby on Rails

问题 Users can add tags to a snippet: class Snippet < ActiveRecord::Base # Relationships has_many :taggings has_many :tags, :through => :taggings belongs_to :closing_reason end I want to validate the number of tags: at least 1, at most 6. How am I about to do this? Thanks. 回答1: You can always create a custom validation. Something like validate :validate_tags def validate_tags errors.add(:tags, "too much") if tags.size > 5 end 回答2: A better solution has been provided by @SooDesuNe on this SO post