Last Updated: 2024-04-24

I had the following

def update_header 
{ 
  item_count: @order.line_items.count,
  total: current_order.display_total
}.to_json
end

In my JavaScript code, I assumed the total key would be something like $30, since that is how current_order.display_total displayed in rspec or irb output

In fact, it turned into a hash in this context: {amount: 30, currency: "$"}, which the JavaScript client-code was totally unprepared to handle.

Lesson

Do not assume anything about the shape of a complex object which is called within a to_json block. The to_s representation in particular should not be expected.