Model.includes(:property) seemingly not working

I'm starting a small Rails project to register iOS devices here at the office, just to learn the framework, and I've come across the following problem:

Given two models "Device" and "Owner" with the following associations:

class Owner < ActiveRecord::Base
  has_many :devices
end

class Device < ActiveRecord::Base
  belongs_to :owner
  belongs_to :os_version
  belongs_to :device_type
end

Schemas are:

CREATE TABLE "devices" (
    "id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
    "uuid" varchar(255), 
    "imei" varchar(255), 
    "device_type_id" integer, 
    "label" varchar(255), 
    "os_version_id" integer, 
    "owner_id" integer, 
    "created_at" datetime, 
    "updated_at" datetime, 
    "serial" varchar(255)
);
CREATE TABLE "owners" (
    "id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
    "first_name" varchar(255), 
    "last_name" varchar(255), 
    "username" varchar(255), 
    "created_at" datetime, 
    "updated_at" datetime
);

I'm trying to get a controller to eagerly fetch an Owner with all its Devices, so I tried the following:

class OwnerController < ApplicationController

  def list
    @owners = Owner.includes(:devices).all
    respond_to do |format|
      format.xml { render :xml=>@owners } 
 开发者_Go百科     format.any(:json, :html) { render :json => @owners }
    end
  end
end

The controller successfully lists all owners, but the devices are nowhere to be found.

I've also tried using default scope in the Owner class, but still no good.

When using rails console, any query using Owner.include(:devices) fails to return device information, but Owner.first.devices has everything in it.

Any ideas on what I might be doing wrong?

Thanks!

You need to specify that your XML and JSON views should include the devices associations:

format.xml { render :xml => @owners.to_xml(:include => :devices) } 

Or, in Rails 3, to make things a little simpler:

class OwnerController < ApplicationController

  respond_to :html, :json, :xml

  def list
    @owners = Owner.includes(:devices).all
    respond_with @owners, :include => :devices
  end

end

AFAIK, the XML and JSON renders don't render associates by default.

For XML, you'll have to explicitly define which associations you want rendered:

format.xml  { render :xml => @owners.to_xml(:include => :devices) }

The same principle (different syntax) applies to JSON rendering.

HTH