Ruby on Rails -主键和外键

Question

我正在用Ruby on Rails创建一个站点，我有两个模型，一个是User模型，一个是Transaction模型。

这两个模型都属于一个帐户，因此它们都有一个名为account_id的字段

我尝试在它们之间建立一个关联，如下所示：

class User < ActiveRecord::Base
  belongs_to :account
  has_many :transactions
end

class Transaction < ActiveRecord::Base
  belongs_to :account
  belongs_to :user
end

我像这样使用这些关联：

user = User.find(1)
transactions = user.transactions

此时，应用程序正在尝试使用user_id查找事务，下面是它生成的SQL：

Mysql::Error: Unknown column 'transactions.user_id' in 'where clause': SELECT * FROM `transactions` WHERE (`transactions`.user_id = 1)

这是不正确的，因为我希望通过account_id查找交易，我已经尝试像这样设置关联：

class User < ActiveRecord::Base
  belongs_to :account
  has_many :transactions, :primary_key => :account_id, :class_name => "Transaction"
end

class Transaction < ActiveRecord::Base
  belongs_to :account
  belongs_to :user, :foreign_key => :account_id, :class_name => "User"
end

这几乎实现了我想要做的事情，并生成了以下SQL：

Mysql::Error: Unknown column 'transactions.user_id' in 'where clause': SELECT * FROM `transactions` WHERE (`transactions`.user_id = 104)

编号104是正确的account_id，但它仍在尝试查询事务表中的user_id字段。谁能给我一些建议，关于我如何设置关联来查询transaction表中的account_id，而不是导致如下SQL查询的user_id：

SELECT * FROM `transactions` WHERE (`transactions`.account_id = 104)

干杯

Eef

Answer 1

class Account < ActiveRecord::Base
  has_many :users
  has_many :transactions
end

class User < ActiveRecord::Base
  has_many :transactions, :through => :account
end

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#M001833

Answer 2

如果transactions表中没有列user_id，那么应该使用Account模型来选择所有事务：

class User < ActiveRecord::Base
  belongs_to :account
end

class Account < ActiveRecord::Base
  has_many :transactions
  has_one :user # or has_many :users
end

class Transaction < ActiveRecord::Base
  belongs_to :account
end

User.find(1).account.transactions

请注意，您必须从User中删除has_many :transactions，从Transaction中删除belongs_to :user，因为它们假定您确实有user_id列。

Answer 3

我想将数据存储在与学生模型相关联的地址模型中

class AddressesController < ApplicationController

    def new
        @address = Address.new      
    end

    def create
        @address = Address.create(:address_date => Time.now,
            :student_id => @student.id)
    end

    private

    def address_params
        params.require(:address).permit(:gali_no, :house_no_flate_no, :vill_town_city, :district, :state, :post_code, :country)
    end
end






class StudentsController < ApplicationController

    def show

    end

    def new
        @student = Student.new
    end

    def create
        @student = Student.new(student_params)

        if @student.save
            redirect_to root_url,  :notice => "You have been registered"
        else
            render "new"
        end
    end

    private
    def student_params
        params.require(:student).permit(:f_name, :l_name, :email, :password, :password_confirmation, :mobile_no)
    end
end


class Student < ActiveRecord::Base

    has_many :addressess, :dependent => :destroy

    attr_accessor :password

    before_save :encrypt_password

    validates_confirmation_of :password
    validates_presence_of :f_name
    validates_presence_of :l_name
    validates_presence_of :password, :on => :create
    validates_presence_of :email
    validates_uniqueness_of :email

    def encrypt_password
        if password.present?
          self.password_salt = BCrypt::Engine.generate_salt
          self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
        end
    end
end




class Address < ActiveRecord::Base

  belongs_to :student

end