Strong parameters and multidimensional arrays

Question

I'm using Rails 3.2.6 with strong parameters gem.

So, I' have a controller with the typical update action:

# PUT /api/resources/:id
def update
  @resource.update_attributes! permited_params
  respond_with_json @resource, action: :show
end

Then, I have the permited_params method

def permited_params
  params.permit(:attr1, :attr2, :attr3)
end

The problem is that :attr3 is a multidimensional array like this: [[1, 2], [2, 5, 7]]

Following the documentation, I need to specify :attr3 as an array. But...

params.permit(:attr1, :attr2, :attr3 => [])
#inspecting permited_params: {"attr1"=>"blah", "attr2"=>"blah"}

params.permit(:attr1, :attr2, :attr3 => [[]])
#inspecting permited_params: {"attr1"=>"blah", "attr2"=>"blah", "attr3" => []}

params.permit(:attr1, :attr2, :attr3 => [][])
#throw error

The question is: How can I use strong params with multidimensional arrays?

Answer 1

You can also do this in this way

   def permited_params
     hash = params.permit(:attr1, :attr2) 
     hash[:attr3] = params.require(:attr3) if params.has_key?(:attr3)
     hash
   end