associations

问题 I'm wondering how I can add associations to my models. Suppose, I generate two models rails generate model User rails generate model Car Now I want to add an associations so that the models acquire the form class User < ActiveRecord::Base has_many :cars end class Car < ActiveRecord::Base belongs_to :user end The question is: how to apply this modification by migrations in order to obtain cars_users table in the database? I'm planning to use that table in my code. 回答1: belongs_to association

问题 I am using ActiveAdmin gem in my project. I have 2 models using has_many through association. The database schema looks exactly the same as the example in RailsGuide. http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association (source: rubyonrails.org) How can I use ActiveAdmin to ... show appointment date of each patient in physicians page? edit appointment date of each patient in physicians page? Thanks all. :) 回答1: For 1) show do panel "Patients" do table_for

问题 I have the following entities: TEAM @Entity @Table public class Team { [..] private Set<UserTeamRole> userTeamRoles; /** * @return the userTeamRoles */ @OneToMany(cascade = { CascadeType.ALL }, mappedBy = "team", fetch = FetchType.LAZY) public Set<UserTeamRole> getUserTeamRoles() { return userTeamRoles; } /** * @param userTeamRoles * the userTeamRoles to set */ public void setUserTeamRoles(Set<UserTeamRole> userTeamRoles) { this.userTeamRoles = userTeamRoles; } } and USER_TEAM_ROLE @Entity

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 2 years ago . In discussion about my answer to this question, there was some disagreement over how to model this code: public class MainClass { private Something something; public void Action() { OtherClass other = something.GetOtherClass(); } } The key points being: the Something class is an

问题 I have set up a file extension in the Registry for my program as Windows requires. In the Registry, under shell/open/command, I've got: "C:\MyProgramPath\MyProgram.exe" "%1" This works fine for me. When someone clicks on one or more files associated with my application, my application correctly opens the file(s) but each one is opened in a separate program instance. Is there any way I can do this and open up all files in one program instance? 回答1: You can when using DDE. See http://cc

问题 New to rails and I'm following the Depot project found in the Agile web development with rails 3.1. Everything was fine until I got lost when the book used the "build" method. @cart = current_cart product = Product.find(params[:product_id]) @line_item = @cart.line_items.build(product: product) My google searches led me to understand that the .build method is just a cleaner way to create a row in the table (with association between tables). But on the code above, I was expecting the code would

问题 This follows this prior question, which was answered. I actually discovered I could remove a join from that query, so now the working query is start_cards = DeckCard.find :all, :joins => [:card], :conditions => ["deck_cards.deck_id = ? and cards.start_card = ?", @game.deck.id, true] This appears to work. However, when I try to move these DeckCards into another association, I get the ActiveRecord::ReadOnlyRecord error. Here's the code for player in @game.players player.tableau = Tableau.new

问题 Could you tell me whats the best practice to create has_one relations? f.e. if i have a user model, and it must have a profile... How could i accomplish that? One solution would be: # user.rb class User << ActiveRecord::Base after_create :set_default_association def set_default_association self.create_profile end end But that doesnt seem very clean... Any suggests? 回答1: Best practice to create has_one relation is to use the ActiveRecord callback before_create rather than after_create . Or use

问题 I'm trying to set up a many to many relationship in EF code first but the default conventions is getting it wrong. The following classes describes the relationship: class Product { public int Id { get; set; } public string Name { get; set; } } class Account { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<Product> Products { get; set; } } One Account can have many Products. However the EF conventions will create the DB tables as: Products Table -------

问题 In this example, I create a user with no profile , then later on create a profile for that user. I tried using build with a has_one association but that blew up. The only way I see this working is using has_many . The user is supposed to only have at most one profile . I have been trying this. I have: class User < ActiveRecord::Base has_one :profile end class Profile < ActiveRecord::Base belongs_to :user end But when I do: user.build_profile I get the error: ActiveRecord::StatementInvalid: