ActiveModel::ForbiddenAttributesError Nested Attributes Strong Params

I am relatively new to rails, but I have successfully used nested attributes in strong params and arrays in strong params. However, I'm really stuck. I am creating a form to update a Model with two later nesting:



Project > Milestones > Tasks.

Instead of the usual model of having a user create the tasks & milestones, the tasks and milestones are already created based on the kind of project using another set of nested attributes.



Template > MilestoneTemplate > TaskTemplate.

When I try to submit my form....I get this:

ActiveModel::ForbiddenAttributesError

These are my models:

template.rb

# == Schema Information
#
# Table name: templates
#
#  id         :integer          not null, primary key
#  name       :string
#  created_at :datetime         not null
#  updated_at :datetime         not null
#

class Template < ActiveRecord::Base

  has_many :milestone_templates
  has_many :projects

    validates_presence_of :name, message: "Template must have a name"
  validates_uniqueness_of :name,  message: "Looks like you\'ve already added this Template."
end

project.rb

# == Schema Information
#
# Table name: projects
#
#  id          :integer          not null, primary key
#  template_id :integer
#  name        :string
#  created_at  :datetime         not null
#  updated_at  :datetime         not null
#

class Project < ActiveRecord::Base

  belongs_to :template
  has_many :milestones
  has_many :tasks
  accepts_nested_attributes_for :tasks, allow_destroy: true
    accepts_nested_attributes_for :milestones, allow_destroy: true

    validates_presence_of :name, message: "Project must have a name"
  validates_uniqueness_of :name,  message: "Looks like you\'ve already added this Project."
  validates :template_id, presence: true
end

milestone_template.rb

# == Schema Information
#
# Table name: milestone_templates
#
#  id          :integer          not null, primary key
#  template_id :integer
#  name        :string
#  created_at  :datetime         not null
#  updated_at  :datetime         not null
#

class MilestoneTemplate < ActiveRecord::Base

    belongs_to :template
  has_many :task_templates, dependent: :destroy
  validates_uniqueness_of :name, scope: :template_id, message: "Looks like you\'ve   already added this Milestone Template."
  validates_presence_of :name, message: "Milestone Template must have a name"
    accepts_nested_attributes_for :task_templates, allow_destroy: true

end

task_template.rb

# == Schema Information
#
# Table name: task_templates
#
#  id                    :integer          not null, primary key
#  template_id           :integer
#  milestone_template_id :integer
#  name                  :string
#  created_at            :datetime         not null
#  updated_at            :datetime         not null
#

class TaskTemplate < ActiveRecord::Base
    belongs_to :milestone_template, inverse_of: :task_templates

    validates_uniqueness_of :name, scope: :milestone_template_id, message: "Looks like you\'ve already added this Task Template."
    validates_presence_of :name, message: " Task Template must have a name"
end

milestone.rb

# == Schema Information
#
# Table name: milestones
#
#  id                    :integer          not null, primary key
#  project_id            :integer
#  milestone_template_id :integer
#  name                  :string
#  created_at            :datetime         not null
#  updated_at            :datetime         not null
#

class Milestone < ActiveRecord::Base

    belongs_to :project
    belongs_to :milestone_template
    has_many :tasks, dependent: :destroy
    validates_presence_of :name, message: "Enter the Milestone Name."
  validates_uniqueness_of :name, scope: :project_id, message: "Looks like you\'ve already added this Milestone."
    accepts_nested_attributes_for :tasks, allow_destroy: true
end

task.rb

# == Schema Information
#
# Table name: tasks
#
#  id               :integer          not null, primary key
#  project_id       :integer
#  milestone_id     :integer
#  task_template_id :integer
#  name             :string
#  created_at       :datetime         not null
#  updated_at       :datetime         not null
#

class Task < ActiveRecord::Base
    belongs_to :project
    belongs_to :milestone
    belongs_to :task_template

    validates_uniqueness_of :name, scope: :project_id, message: "Looks like you\'ve already added this Task to this Project."
  validates_presence_of :name, message: " Task must have a name"
end

_form.html.erb

<%= form_for @project do |f| %>
  <% @milestones_templates.each_with_index do |milestone, index| %>
    <br>
    <%= f.fields_for :milestones, index: index do |fm| %>
      <%= fm.hidden_field :name, value: milestone.name %>

      <!-- Create a checkbox to add the milestone_id to the project -->
      <%= fm.label milestone.name %>
      <%= fm.check_box :milestone_template_id,  value: milestone.id %>
      <br>
      <% milestone.task_templates.each_with_index do |task, another_index| %>
        <%= fm.fields_for :tasks, index: another_index do |ft| %>
          <!-- Create a checkbox for each task in the milestone -->
          <%= ft.label task.name %>
                <%= fm.hidden_field :name, value: task.name %>

          <%= ft.check_box :task_template_id,  value: task.id %>
        <% end %>
      <% end %>
      <br>
    <% end %>
  <% end %>
  <br>
<%= f.submit %>
    <% end %>

projects_controller.rb

class ProjectsController < ApplicationController
 def new_milestones
    @project.milestones.build
    @project.tasks.build
    @milestones_templates = MilestoneTemplate.where(template_id: @project.template_id)
  end

  def update
    respond_to do |format|
      result = ProjectUpdater.perform(@project, project_params, params) == true
      if result == true
        format.html { redirect_to @project, notice: 'Project was successfully updated.' }
        format.json { render :show, status: :ok, location: @project }
      else
        @project = result
        format.html { render :edit }
        format.json { render json: @project.errors, status: :unprocessable_entity }
      end
    end
  end

    def project_params
      params.require(:project).permit(:id, :name, milestones_attributes: [:name, :id, :project_id, {:milestone_template_ids =>[]}, :_destroy, tasks_attributes: [:id,  :project_id,  :name, {:task_template_ids =>[]}, :_destroy ] ] )
    end

lib/project_updater.rb**This is very new for me...so mistakes might be here.

class ProjectUpdater

def self.perform(project, params, project_params)
    milestones = params[:milestones]

    if project.update_attributes(project_params)
      return true
    else
      return project
    end
  end
end