Rails的模型，有两个“HAS_ONE'和'的has_many”但也有一些约束上 [英] Rails model that has both 'has_one' and 'has_many' but with some contraints
问题描述
我映射2款：
User
Account
class Account
has_many :users
class User
has_one :account
用户表作为它的ACCOUNT_ID。
The user table as the account_id in it.
现在的客户模式，我想创建一个主要用户，这一个账户只有1了。 用户表中有一个布尔标志：is_primary，我怎么能创建的帐户侧谁拥有is_primary和ACCOUNT_ID映射用户的HAS_ONE
Now on the Account model I want to create a 'primary user' which an account only has 1 off. The user table has a boolean flag :is_primary, how can I create a has_one on the account side for a user who has the is_primary and account_id mapped.
所以SQL就像：
SELECT * FROM users where account_id=123 and is_primary = 1
于是我想：
一个用户帐户。 一个帐户拥有众多用户，并拥有一个主要用户也。
A user has an account. An account has many users, and has a single primary user also.
推荐答案
方法1 - 添加一个新的关联
添加 HAS_ONE 协会与其中，拉姆达。这使您能够将当前架构内工作。
Add an has_one association with a where lambda. This allows you to work within your current schema.
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 - 添加的关联方法
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
这篇关于Rails的模型，有两个“HAS_ONE'和'的has_many”但也有一些约束上的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
