Question

Here are the model relationships:

class Tool < ActiveRecord::Base
  ...
  has_many :loss_ratios, :dependent => :destroy, :order => "loss_ratios.starts_at DESC"

  validates_associated :loss_ratios
  accepts_nested_attributes_for :loss_ratios, :allow_destroy => true

  attr_accessible :name, :text, :service_id, :supplier_id, :loss_ratios_attributes
end

class LossRatio < ActiveRecord::Base
  belongs_to :tool

  validates :rate, :starts_at, :tool, :presence => true
  validates_uniqueness_of :starts_at, :scope => :tool_id
  validates_numericality_of :rate
  validates_inclusion_of :rate, :in => (0..1)
  ...
end

I’m managing LossRatio associations in the create/update ToolsController actions. I want to test those by POSTing sets of attributes for a Tool (including a couple of nested LossRatios as though they were submitted in a form). I’m using FactoryGirl, but it doesn’t seem to have a way of constructing a params-like hash of attributes (attributes_for ignores associations, and looks like this behavior is not gonna change).
Is there a way to do this?

(I know the title is a mess, but I couldn’t think of anything better and shorter…)

Answer 1

OK here’s what I’ve come up with after pulling my hair out for half a day:

def params_for(factory_name)
  exclude_params = [ "id", "created_at", "updated_at" ]
  f = FactoryGirl.build(factory_name)

  params = f.attributes.except(*exclude_params).dup

  f.reflections.select { |k,v|
    v.macro == :has_many && !v.instance_of?(ActiveRecord::Reflection::ThroughReflection)
  }.each_key do |k|
    assoc_collection = f.send(k)

    unless assoc_collection.empty?
      params["#{k.to_s}_attributes"] = {}

      assoc_collection.each_with_index do |assoc_obj,idx|
        params["#{k.to_s}_attributes"][idx.to_s] = assoc_obj.attributes.except(*exclude_params << "#{f.class.name.underscore}_id")
      end
    end
  end

  params
end

This is a helper method used for building a params hash consumable by a controller’s CRUD actions. I’m using it in my controller specs like so:

subject { post :create, :tool => params_for(:tool_with_lr_history) }

it "creates a new tool" do
  expect { subject }.to change(Tool, :count).by(1)
end

As seen from the snippet, the method only populates attributes for has-many associations (and ignores has-many-through associations). I guess it might be extended for any kind of relationships, but that works for me so far (unless there’s a better way of doing what I want)…