A Generalized Json Controller for use with extjs-mvc and Restful CRUD

json_controller.rb

class JsonController < ApplicationController

  rescue_from ActiveRecord::RecordNotFound do |exception|
    render :json => { :success => false }, :status => :not_found
  end

  before_filter :find_record, :only => [ :get, :update, :destroy ]

  layout 'base'

  class << self
    attr_accessor :model_class
  end

  def self.active_record_model_class (in_model)
    #if a model is passed in use that, if anything else lookup it up
    self.model_class = in_model.is_a?(ActiveRecord::Base) ? in_model : in_model.to_s.camelcase.constantize
  end

  def index
    respond_to do |format|
      format.html
      format.json {
          @record_hashes ||= scoped_model.all.map(&:to_record)
          render :json => {:success => true, :total => @record_hashes.length, :data => @record_hashes }
        }
    end
  end

  def create
    reject_non_attributes

    @record = scoped_model.new(params[:data])
    success = @record.save
    error_messages = success ? nil : @record.errors.full_messages.join(', ')
    
    render :json => {
      :success => success,
      :message => error_messages || "Created the record",
      :data => @record.to_record}
  end

  def update
    reject_non_attributes
    
    success = @record.update_attributes(params["data"])
    error_messages = success ? nil : @record.errors.full_messages.join(', ')

    render :json => {
      :success => success,
      :message => error_messages || "Updated the record",
      :data => @record.to_record}
  end

  def destroy
    success = @record.destroy
    render :json => {
      :success => success,
      :message => "Deleted the record"}
  end
  
protected

  def find_record
    @record = scoped_model.find(params[:id]) if params[:id]
  end

  def reject_non_attributes()
    #remove incoming attributes that aren't really columns
    names = model.column_names
    params["data"].reject!{|key, value| !names.include? key} if params["data"]
  end

  def scoped_model
    model
  end

  def model
    self.class.model_class ||= model_from_controller_name
  end

  def model_from_controller_name
    #try to infer the model name from the controller if it hasn't been set
    controller = controller_class_name.sub(/Controller$/, '')
    controller.singularize.constantize
  end
end