Sinatra Basics

ruby_sintata.rb

require 'sinatra'
require 'sinatra/param'
require 'sinatra/json'

set :raise_sinatra_param_exceptions, true
set :show_exceptions, false

get '/hi' do
  param :param1,    Float,  required: true
  param :param2,    Float,  required: true
  param :operation, String, in: ['plus', 'minus']

  result = params['param1'] + params['param2']

  json({ calculation: { result: result } })
end

error Sinatra::Param::InvalidParameterError do
  status 422
  { error: "#{env['sinatra.error'].param} is invalid" }.to_s
end