Rails模型既有'has_one'又有'has_many'但有一些约束

Question

我正在映射2个模型:

User
Account

class Account 
  has_many :users


class User
  has_one :account

用户表作为其中的account_id.

现在在帐户模型上我想创建一个帐户只有1个关闭的"主要用户".用户表有一个布尔标志:is_primary,如何在帐户端为具有is_primary和account_id映射的用户创建has_one.

所以SQL看起来像:

SELECT * FROM users where account_id=123 and is_primary = 1

所以我想:

用户拥有一个帐户.帐户有很多用户,并且还有一个主要用户.

Answer 1

方法1 - 添加新关联

添加has_one与wherelambda 的关联.这允许您在当前架构中工作.

class Account 
  has_many :users
  has_one  :primary_user, -> { where(is_primary: true) }, :class_name=> "User"
end

现在:

account.users #returns all users associated with the account
account.primary_user #returns the primary user associated with the account
# creates a user with is_primary set to true
account.build_primary_user(name: 'foo bar', email: 'bar@foo.com')

方法2 - 添加关联方法

class Account 
  has_many :users do
    def primary
      where(:is_primary => true).first
    end
  end
end

现在:

account.users.primary # returns the primary account

Answer 2

将primary_user_id字段添加到Account并为primary_user添加'has_one'关联可能更简单:

class Account
  has_many :users
  has_one :primary_user, :class_name => "User"
end

class User
  has_one :account
end

如果必须使用现有模式(使用:is_primary boolean标志),则可以添加如下范围:

class User
  has_one :account
  scope :primary, where(:is_primary => true)
end

然后将范围链接到用户查找:

account = Account.find(1)
primary_user = account.users.primary.first