Ruby on rails 有没有一种方法可以使用命名作用域过滤加入的关联?
我有以下相关模型Ruby on rails 有没有一种方法可以使用命名作用域过滤加入的关联?,ruby-on-rails,named-scope,Ruby On Rails,Named Scope,我有以下相关模型 class Enrollment < ActiveRecord::Base has_many :addresses end class Address < ActiveRecord::Base belongs_to :address_type end 班级注册
class Enrollment < ActiveRecord::Base
has_many :addresses
end
class Address < ActiveRecord::Base
belongs_to :address_type
end
班级注册
目前,我正在使用以下方法(我认为这很难看)来筛选某个地址类型的注册地址
class Enrollment < ActiveRecord::Base
def local_address
adds = []
addresses.each do |add|
adds << add if add.address_type.name == 'Local'
end
adds.last
end
end
班级注册
class Address < ActiveRecord::Base
belongs_to :address_type
named_scope :local, { :conditions => { :address_type => { :name => "Local" }}}
end
命名范围在您仅使用“本地”地址的所有情况下都会有所帮助。参考下面的stackoverflow帖子,我成功地解决了命名范围查询
基本上,我需要在查询中进行连接
class Address < ActiveRecord::Base
belongs_to :address_type
named_scope :local, {
:joins => "INNER JOIN address_types ON address_types.id = addresses.address_type_id",
:conditions => "address_types.name = 'Local'"
}
end
类地址“地址类型上的内部连接地址类型。id=地址。地址类型\U id”,
:conditions=>“address_types.name='Local'”
}
终止
因此,我可以有效地将注册的“本地地址”方法重写为
clss Enrollment < ActiveRecord::Base
def local_address
addresses.local.last
end
end
clss注册
您的解决方案出现以下错误。Mysql::错误:“where子句”中的未知列“address\u type.name”:从addresses
where(addresses
.incrolment\u id=8)和(address\u type
name
='Local')以及(addresses
.incrolment\u id=8))按地址排序。id DESC LIMIT 1似乎我们必须使用join语句。
clss Enrollment < ActiveRecord::Base
def local_address
addresses.local.last
end
end