ruby on rails - no implicit conversion of Symbol into Integer on nested attributes -

i having issues editing nested attributes. i'm getting error :

no implicit conversion of symbol integer

event.rb:

class event < activerecord::base   has_many :event_joins, :dependent => :destroy   accepts_nested_attributes_for :event_joins end

events_controller.rb :

private    def event_params      params.require(:event).permit(event_joins_attributes: [:duration])     end

_form.html.erb :

 =f.fields_for :event_joins_attributes |a|     =number_field_tag 'event[event_joins_attributes][duration]'  end

if change params before permission

params[:event][:event_joins_attributes][:duration] = params[:event][:event_joins_attributes][:duration].to_i

i have following error:

no implicit conversion of string integer

i've read lot of posts nested attributes mass-assignment nothing works. here part of posts i've read.

of course, don't want do

params.require(:event).permit!

you have change this

=f.fields_for :event_joins_attributes |a|    =number_field_tag 'event[event_joins_attributes][duration]' end

=f.fields_for :event_joins |a|    =a.number_field :duration end

so can have event_params unchanged.

imp note:

also permit :id in event_params update work correctly.

def event_params   params.require(:event).permit(:id, event_joins_attributes: [:id, :duration])  end

WIKI