ex.rb

def create
  # when a create occurs somthing like this is sent to server with a POST request.....
  {
    "utf8"=>"✓",
    "authenticity_token"=>"some/crazy/token",
    "transaction"=>{"name"=>"chik-fil-a",
                    "category_id"=>"1",
                    "amount"=>"1.1"},
    "commit"=>"Create Transaction"
  }
  
  # look at line 4 "transaction"=> that to access it you do 
  params[:transaction]
  # params is the hashmap or dictionary variable name
  # java you would params.get("transaction");
  # so :transaction is the "key"
  #
  # so.. to get category_id
  params[:transaction][:category_id]
  # or java params.get("transaction").get("category_id");
  
  # so now look...
  params.require(:transaction).permit(:name, :category_id, :amount)
  # it means given the params make sure(require) there is a key ":transaction"
  # then is says given that dictionary or map only allow the keys listed. if only
  # those are present then it passes

end