Question

我有以下型号：

class ServiceProvider < ActiveRecord::Base
    has_many :versions, class_name: "ServiceProviderVersion"
end

class ServiceProviderVersion < ActiveRecord::Base
  belongs_to :service_provider
  has_many :service_provider_roles, :through => :service_provider_to_role_maps
  scope :effective, -> { where("effective_date <= ?", Time.now).order('effective_date desc') }
end

class ServiceProviderToRoleMap < ActiveRecord::Base
  belongs_to :service_provider_version
  belongs_to :service_provider_role   
end

class ServiceProviderRole < ActiveRecord::Base
  validates :name, presence: true, uniqueness: true

  has_many :service_provider_versions, :through => :service_provider_to_role_maps
  has_many :service_provider_to_role_maps, :dependent => :destroy 
end

现在我正在努力让所有有效且属于特定角色的服务提供商。理想情况下，我想做以下

ServiceProviderVersion.effective.by_role('Admin')

但是，因为ServiceProviderVersion.effective返回的不仅仅是一条记录，我无法在ServiceProviderVersion上定义一个范围，该范围将按角色进行过滤。

有没有办法实现这个目标？我正在使用Rails4

Answer 1

尝试类似：

class ServiceProviderRole < ActiveRecord::Base
   scope :by_role, ->(name) { where(name: name) }

class ServiceProviderVersion < ActiveRecord::Base
    scope :by_role, ->(name) { joins(:service_provider_roles).merge(ServiceProviderRole.by_role(name)) }

然后你可以打电话：

ServiceProviderVersion.effective.by_role('Admin')

从作用域访问has_many

1 个答案: