Convert integer-keyed Hash parameters to Arrays in Rails

_README.md

Fix for strong_parameters when using accepts_nested_attributes_for

The following before filter looks for any Hash parameters where all the keys are integers and turns them into Arrays. It searches recursively to allow the used of nested attributes within nested attributes. This is necessary to circumvent a bug in the strong_parameters gem which was reported in April 2012. Given params like:

{
  "person" => {
    "dogs_attributes" => {
      "0" => {
        "name" => "Fido"
      },
      "1" => {
        "name" => "Rocket"
      }
    }
  }
}

It will modify them to look like:

{
  "person" => {
    "dogs_attributes" => [
      {
        "name" => "Fido"
      },
      {
        "name" => "Rocket"
      }
    ]
  }
}

How to use

Simply copy the before_filter macro and repair_nested_params method below into your application controller.

application_controller.rb

class ApplicationController < ActionController::Base
  before_filter :repair_nested_params

  protected

  # Fixes nested attribute params for strong_parameters (turns string keyed hash
  # into array of hashes)
  def repair_nested_params(obj = params)
    obj.each do |key, value|
      if value.is_a? Hash
        # If any non-integer keys
        if value.keys.find {|k, _| k =~ /\D/ }
          repair_nested_params(value)
        else
          obj[key] = value.values
          value.values.each {|h| repair_nested_params(h) }
        end
      end
    end
  end
end

For rails 5

  def repair_nested_params(obj)
    obj.each do |key, value|
      if value.is_a? ActionController::Parameters || value.is_a? Hash
        # If any non-integer keys
        if value.keys.find {|k, _| k =~ /\D/ }
          repair_nested_params(value)
        else
          obj[key] = value.values
          value.values.each {|h| repair_nested_params(h) }
        end
      end
    end
  end

TFW when the first google result is an answer you posted to your own question years ago

this really work ?