同时具有“ has_one”和“ has_many”但有一些约束的Rails模型 [英] Rails model that has both 'has_one' and 'has_many' but with some constraints

问题描述

我正在映射2种模型：

User
Account

class Account 
  has_many :users


class User
  has_one :account

用户表作为其中的account_id。

The user table as the account_id in it.

现在在Account模型中，我想创建一个主要用户，该用户的帐户只有1个关。
用户表中有一个布尔标志：is_primary，我如何为具有is_primary和account_id映射的用户在帐户端创建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.

因此，SQL如下所示：

So the SQL would look like:

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

所以我想要：

一个用户有一个帐户。
一个帐户有多个用户，并且也有一个主要用户。

A user has an account. An account has many users, and has a single primary user also.

推荐答案

方法1-添加新的关联

添加 has_one 关联，并在位置 lambda。这使您可以在当前架构下工作。

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: '[e-mail]')

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

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