activerecord

问题 Looking into passing a variable as value on ActiveRcord query key/column? login = Login.where("email_address" => "geo@bostj.com","active" => 1).select("id") => [#<Login id: 767>] login = Login.where("email_address" => "geo@bostj.com","active" => 1).select("id").class => ActiveRecord::Relation admin = Admin.where("login_id"=>login).exists? Heeeelp 回答1: I would do: login = Login.where(email_address: 'geo@bostj.com', active: 1) Admin.exists?(login_id: login.pluck(:id)) 回答2: You can write as

问题 I am using an existing database with a rails app. I can't change the table or column names. Lets say table one is "invoices" and table 2 is "orders" they both have a primary key that is called the same thing, lets say "order_id" invoices can find its order by looking at the primary key "order_id" in the orders table. Vice versa for an order finding its invoice. Invoices can have but not always have one order (you might be invoiced for something besides an order, like a "work_order" which

问题 I have an Artist model that has many Album s in a HABTM association. Though I would like to permit two different albums to have the same name I'd like to ensure that there aren't two in the collection of one artist. So far example: artist_1 = Artist.create(name: "Jay-Z") artist_2 = Artist.create(name: "The Beatles") album_1 = Album.create(name: "The Black Album", artist_ids: [1]) album_2 = Album.create(name: "The Black Album", artist_ids: [1]) => Should return error album_2 = Album.create

问题 I currently have three models that I am interested in: Region, Seat and User. Region has many seats and seats have many available users. I'd like to know what is the most efficient way in Rails to retrieve all of the available users for the seats which sit under a particular region. Thanks in advance. 回答1: Try: User.joins(seat: :region).where(regions: { id: REGION_ID_HERE }) 回答2: I think the nested join syntax by @cschroed might not work depending on how your data model is set up. If it doesn

问题 I'm building a football game and I'm having trouble creating Club and Match classes. I want to be able to do this: match = Match.find(2) match.home_club = <some club here> match.away_club = <other club here> And also this: club = Club.find(2) club.matches # Returns all matches where club plays home or away This is what I have now: class Club < ActiveRecord::Base has_many :matches end class Match < ActiveRecord::Base belongs_to :home_club, :class_name => "Club" belongs_to :away_club, :class

问题 I have a Rails 3.2.14 app that tracks calls and each call has a pickup and dropoff facility from the Facility model which is an association. In the call model there is an association for the Region model (i.e. Houston, Dallas, Austin, etc) where we select a region based on where the call is coming from. What I'd like to do is be able to select a specific region (i.e. Houston) and in the pickup facility collection only show Houston region facilities. I'm assuming to start off with I'd need to

问题 Trying to find the mutual relation, In a friends relations, Already have friends and inverse_friends. But how to combine them to get the mutual friends? Cannot seem to figure it out I tried several options and searched long time online, just don't see it has_many :friendships has_many :friends, :through => :friendships has_many :inverse_friendships, :class_name => "Friendship", :foreign_key => "friend_id" has_many :inverse_friends, :through => :inverse_friendships, :source => :user how to get

问题 I have inherited a Rails 3 app that stores much of it's data as a fairly sophisticated tree structure. The application works pretty well in general but we are noticing some problems with performance, mostly around database interactions. I am seeing a lot of queries along the lines of these showing up in my logs: SELECT `messages`.* FROM `messages` WHERE `messages`.`context_type` = 'Node' AND `messages`.`context_id` IN (153740, 153741, /* about a thousand records... */ 154837, 154838, 154839,

问题 Lets start with code that may go like this: class User < ActiveRecord::Base has_many :photos has_many :submitted_photos has_many :posted_photos has_many :handshakes, through: :photos end class Photo < ActiveRecord::Base belongs_to :user end class PostedPhoto < Photo has_many :handshakes, inverse_of: :poster, foreign_key: 'poster_id' end class SubmittedPhoto < Photo has_many :handshakes, inverse_of: :submitter, foreign_key: 'submitter_id' end class Handshake < ActiveRecord::Base belongs_to

问题 I've got a tiny model (let's call it "Node") that represents a tree-like structure. Each node contains only a name and a reference to its father: class Node < ActiveRecord::Base validates_presence_of :name, :parent_id end The table isn't very big - less than 100 elements. It's updated rarely - in the last 4 months 20 new elements were added, in one occasion, by the site admin. Yet it is used quite a lot on my application. Given its tree-like structure, on some occasions a request triggers