Unwrap Rails POST params hash and map to model attributes w/ strong parameters

Question

I am building a rails4 api where i am posting a nested hash of attributes. however, the model does not actually have nested attributes or an association. Attempting to make a cleaner post params hash by combining some attributes into a group, but have the api handle the unwrapping and strong parameters validation.

## Example POST params
params[:item][:group] = {
  a: true,
  b: false
}

But the model does not actually have a group column, the attributes a and b are attributes directly on the model.

to handle this without the group wrapper would simply be

params.require(:item).permit(:a, :b)

But I would like to have it pass strong_parameters submitted with the group wrapper. How can I achieve this but having the POST params as mentioned above?

Answer 1

like most ruby/rails situations there's likely a better way of doing this. grabbing from the responses i end up with this seemingly hack approach. the important thing is that it does what i'm looking for, but it feels icky so if someone has a more elegant way please share!

class YourController < ApplicationController

private

  ## POST { item: { group: { a: true, b: false } } }
  def item_params
    group = params[:item][:group].presence

    if group
      ## Unwrap nesting and place at root of params[:item]
      ## Probably should explicitly handle this instead of iterating
      group.each {|k,v| params[:item][k] = v }
      params[:item].delete :group
    end

    params[:item].permit(:a, :b)
  end
end