activerecord

问题 I have a Character model and a Link model. The Link model represents a link from a character to another character. A link has a textual 'description' attribute. A link from character A to character B is distinct from the opposite link from B to A. A character has zero or one link to another character. A character may have various links to different characters. A character may be linked to by various different characters. I used used Active Record relationships to partly implement

问题 I have a specific example, but the general question is: whats the optimal way to retrieve records when you have an array of filter values to match? Say I have User and Post records where User has_many :posts and I have a Relationship model that looks like this: class Relationship < ActiveRecord::Base belongs_to :follower, class_name: "User" belongs_to :followed, class_name: "User" validates :follower_id, presence: true validates :followed_id, presence: true end I want to write a function that

问题 I'm building an application that consumes models through an api with ActiveResource. I noticed that the @resource ||= @resource.do a query doesn't work, i.e. If I put something like that in my controller, my application will still query the api. So there is no built in caching that I'm used to with ActiveRecord. Time to expand my knowledge and skill base, ok. I found this: http://injectisforwizards.com/blog/read-through-caching-of-activeresource/, and while I don't understand this 100% yet,

问题 For a couple of years, I've worked to make a database that holds the data for an incredibly-complicated engineering process. Right now, it's served by an SQL Server database in Azure, with a WinForms (w/ DevExpress) client, and an Azure worker role for doing a couple of long-running processes which center on our main file format, and a library which operates on it. I've written a data-access library that's essentially a really crappy ORM. I'm tired of this architecture. All along, I've

问题 I am using Ruby Workflow in my ActiveRecords using Gem: Workflow Existing Running Code contains: I am having an ActiveRecord: X I am having two Migrations already: (Ref1) CreateX migration (which creates table X) (Ref2) CreateInitialEntryInX migration (which creates one entry in table X) New Changes: Now I wanted to add workflow in ActiveRecord X, hence I did: (Ref3) I added the workflow code in ActiveRecord Model X (mentioning :status as my workflow field) (Ref4) AddStatusFieldToX migration

问题 Given User and Book models, I've created a join model, ViewedBook, that contains additional attributes. Below is the essence of what I've come up with: create_table "users" t.string "username" end create_table "books" t.string "title" t.integer "user_id" t.date "authored_date" end create_table "books_viewings" t.integer "book_id" t.integer "user_id" t.boolean "finished" t.date "last_viewed_date" end class User belongs_to :book_viewing has_many :authored_books, :class_name => "Book", :source =

问题 I wish to set up nested comments, and want to use self-join to set this up. class Comment < ActiveRecord::Base has_many :children, :class_name => 'Comment' #... end Now, what sql table structure would I use to set up the has_many self-join? I'm assuming something like this: comment_to_comments: parent_id integer child_id integer How do I tell rails to use this table? How do I tell rails that parent_id is the foreign key to reach the parent and the child_id is the foreign key to reach the

问题 I'm a newbie to Ruby and web development. I'm using Windows 7 64-bit with Ruby 2.0 and I have PostgreSQL 9.4 installed. I'm trying to use ActiveRecord to create a database. I checked that my postgresql server is running and I did bundle install to make sure I had all the required gems. However, when I try to do the terminal command "bundle exec rake create:db" it tells me that "'createdb' is not recognized as an internal or external command, operable program or batch file." I also did the

问题 I have a Rails Model: ruby-1.9.2-p0 > NavItem => NavItem(id: integer, item_identifier: string, description: string, description2: string, packing_unit: string, sales_unit_of_measure: string, ean_code: string, evp_price: string, item_category_code: string, class: string, product_group_code: string, maintenance_status: string) If I want to create a record: ruby-1.9.2-p0 > NavItem.create NoMethodError: undefined method `has_key?' for nil:NilClass from /Users/amueller/.rvm/gems/ruby-1.9.2-p0/gems

问题 I have this sql query SELECT * FROM adm_species t JOIN adm_breeds e ON e.species_id = t.id JOIN fd_registrations s ON s.breeds_id = e.id WHERE t.code = 'cat' AND s.sex_id = '2' AND s.ownername LIKE '%sha%' How do I convert this to Codeigniter Active Record? Thanks in advance! 回答1: Try this $this->db->select('*'); $this->db->from('adm_species t'); $this->db->join('adm_breeds e', 'e.species_id = t.id'); $this->db->join('fd_registrations s', 's.breeds_id = e.id'); $this->db->where('t.code', 'cat