ruby-on-rails - "RuntimeError unknown class:"访问 "joins"操作的结果时

Question

当试图访问 Model.joins(ActiveRecord::Relation) 的结果时运行，出现错误。

型号如下:

class Device < ActiveRecord::Base
    has_one :android_device

    def Device.find_devices_by_attributes(device_params)
        android_devices = AndroidDevice.find_android_devices_by_attributes(device_params[:android_device_attributes])

        if (!android_devices.nil?) && (!android_devices.empty?)
            devices_android_device = Device.joins(android_devices)   <--- this is the line the error occures on.
        end
    end
end

class AndroidDevice < ActiveRecord::Base
    belongs_to :device

    def AndroidDevice.find_android_devices_by_attributes (android_params)
        android_devices = AndroidDevice.where("android_id = ?", android_params[:android_id])
    end
end

日志显示:

2014-05-21T08:46:14.719594+00:00 app[web.1]: Completed 500 Internal Server Error in 87ms
2014-05-21T08:46:14.721376+00:00 app[web.1]: RuntimeError (unknown class: AndroidDevice):

两者， Device和 AndroidDevice , 通过命令 rails g scaffold ... 创建

我不明白为什么 AndroidDevice是一个未知的类。

Answer 1

您不能使用 .joins以 ActiveRecord::Relation 作为参数。

可能你想要 http://apidock.com/rails/ActiveRecord/SpawnMethods/merge功能。