associations

问题 I'm having hard times figuring out why this doesn't work on my computer. I've read this article http://msdn.microsoft.com/en-us/library/bb776820.aspx and tried it, and it works for an unknown file type, but for know such as .bmp it doesn't - I've also deleted other keys under .bmp - didn't help. I've tried this in HKEY_CLASSES_ROOT.bmp and in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts.bmp I need to implement this in my program so it has custom context menu

问题 I have a model named Post (blog post) and a model named Category . Each post belongs_to a category. Each category has an attribute named retainer that specifies the amount of time before a post "expires", so for example movies_category.retainer = 30.days What I'm trying to do is create a scope for Post that finds all of the posts which are "expired". So for example, assuming I were to hardcode the value of 30.days and it were to apply to all categories (therefore all posts), the scope would

问题 I have this User and team model which has the following association: user.rb class User < ActiveRecord::Base belongs_to :team team.rb class Team < ActiveRecord::Base has_many :users has_one :leader, class_name: "User", foreign_key: "leader_id" belongs_to :manager, class_name: "User", foreign_key: "manager_id" but it seems that I can't imagine representing it properly into a migration. At first, this is what I did: class AddTeamIdToUsers < ActiveRecord::Migration def change add_column :users,

问题 Organization and User have a many-to-many association through Relationship . Initially I implemented this a 1-to-many association, which worked but now I need it to become a many-to-many through association. So I created the Relationship model and changed the association in the model files. Organization accepts nested attributes for User as in my app I have a joined signup form for the two. Also, I use it in my seeds file: Organization.create!(name: "name", ...).users.create(email: "email

问题 I have two models: (Albums and Product) 1) Inside Models Inside album.rb: class Album < ActiveRecord::Base attr_accessible :name has_many :products end Inside product.rb: class Product < ActiveRecord::Base attr_accessible :img, :name, :price, :quantity belongs_to :album end 2) Using " rails console ", how can I set the associations (so I can use "<%= Product.first.album.name %>")? e.g. a = Album.create( :name => "My Album" ) p = Product.create( :name => "Shampoo X" ) # what's next? how can i

问题 Is @JoinColum implicitly specified when we use any association type annotation like @OneToOne , @OneToMany , etc. Here is snippet from Student entity in association with Laptop entity Case 1) Without using explicit @JoinColum @OneToMany(cascade=CascadeType.ALL) private List<Laptop> laptops=new ArrayList<Laptop>(); Case 2) Using explicit @JoinColum @OneToMany(cascade=CascadeType.ALL) @JoinColumn private List<Laptop> laptops=new ArrayList<Laptop>(); When I check DEBUG both cases have "almost"

问题 I have two models, App and User , where an App has a creator who is a User . # app.rb class App < ActiveRecord::Base belongs_to :creator, class_name: 'User' end # user.rb class User < ActiveRecord::Base has_many :apps, foreign_key: "creator_id" end How do I create fixtures for this? I tried: # apps.yml myapp: name: MyApp creator: admin (User) # users.yml admin: name: admin But this doesn't work, since the relation is an aliased foreign key, not a polymorphic type. Omitting the (User) in the

问题 I have two associated tables. Venues and Specials . A venue can have many specials . Once a user has created a venue I wish to allow them to create a special on the venues#index page. By using nested resources I have achieved the desired URL: /venues/5/specials/new . However, my current code results with: No route matches {:controller=>"specials", :format=>nil} I'm guessing the error is with my SpecialsController and the def new and def create functions. I would like the URL to take me to a

问题 I thought it was possible to create a new model object through an association. class Order < ActiveRecord::Base belongs_to :basket end class Basket < ActiveRecord::Base has_one :order end order = Order.new() basket = order.basket.new() # NoMethodError: undefined method `new' for nil:NilClass 回答1: It is, but your syntax is a little wrong: class Order < ActiveRecord::Base belongs_to :basket end class Basket < ActiveRecord::Base has_one :order end order = Order.new() basket = order.create_basket

问题 Based on following models class Company < ActiveRecord::Base belongs_to :country end class Country < ActiveRecord::Base has_many :companies end I want to have in my companies/_form a select tag containing all the countries I think that the Company.new(params[:company]) in companies_controller#create can create the association between company and the selected country I'm running rails 3.0.0, what is the best way to achieve that? thanks for your insights 回答1: collection_select should do the