1 params = ActionController::Parameters.new(user: { name: 'Francesco', age: 22, role: 'admin' })
2 permitted = params.require(:user).permit(:name, :age)

permitted.permitted?      # => true
permitted.has_key?(:name) # => true
permitted.has_key?(:age)  # => true
permitted.has_key?(:role) # => false

1 class Admin::Column < ActiveRecord::Base
2  ……
3   attr_accessible :user_id , :has_child , :parent_id , :title , :icon
4   ……
5 end

1 class Admin::ColumnsController < ApplicationController
2   ……
3   def admin_column_params
4       params[:admin_column]
5   end
6   ……
7 end

1 if admin_column_params.has_key?(:icon) 
2    puts admin_column_params.require(:icon)
3 end