CODEWITHSUNDEEP
rubyexceptionsinatra
Captain Stack
Captain Stack

Reputation: 3844

How to gracefully handle exceptions in a Sinatra API

I'm trying to write an API in Sinatra that accepts a temporary CSV file as a parameter. I want to raise an exception if the filetype isn't text/csv or if the CSV doesn't have an email column, and I wanted the confirmation page to simply display the error message. I imagined it to look something like this:

if params[:recipients_file]
  raise ArgumentError, 'Invalid file. Make sure it is of type text/csv.' unless params[:recipients_file][:type] == "text/csv"
  recipients_csv = CSV.parse(params[:recipients_file][:tempfile].read, {headers: true})
  raise ArgumentError, 'Invalid CSV. Make sure it has an "email" column' unless recipients_csv.headers.include?('email')
  recipients += recipients_csv.map {|recipient| recipient["email"]}
end

However, any time one of those conditions isn't met, I get really ugly error messages like NoMethodErrors etc. I just want the API to stop execution and to return the error message on the confirmation page. How do I do this?

Upvotes: 0

Views: 1208

Answers (2)

Mr. Programmer
Mr. Programmer

Reputation: 3103

Step 1. First, you should add this line of code in your main app.rb or server.rb(whatever the name of your file) so that it will catch your error block below.

set :show_exceptions, false

Step 2. The exception object can be obtained from the sinatra.error Rack variable. To catch all error then add this error block e.g. code error do...

error do
  env['sinatra.error'].message
end

Upvotes: 0

C. K. Young
C. K. Young

Reputation: 223183

You should define an error block:

error do
  env['sinatra.error'].message
end

See http://www.sinatrarb.com/intro.html#Error for more details, including how to set up different error handlers for different exception types, HTTP status codes, etc.

Upvotes: 5

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