Standardizing api responses in a modular Sinatra application - ruby

Question

I'm developing an api as a modular Sinatra web application and would like to standardize the responses that are returned without having to do so explicitly. I thought this could be achieved by using middleware but it fails in most scenarios. The below sample application is what I have so far.
config.ru
require 'sinatra/base'
require 'active_support'
require 'rack'
class Person
attr_reader :name, :surname
def initialize(name, surname)
#name, #surname = name, surname
end
end
class MyApp < Sinatra::Base
enable :dump_errors, :raise_errors
disable :show_exceptions
get('/string') do
"Hello World"
end
get('/hash') do
{"person" => { "name" => "john", "surname" => "smith" }}
end
get('/array') do
[1,2,3,4,5,6,7, "232323", '3245235']
end
get('/object') do
Person.new('simon', 'hernandez')
end
get('/error') do
raise 'Failure of some sort'
end
end
class ResponseMiddleware
def initialize(app)
#app = app
end
def call(env)
begin
status, headers, body = #app.call(env)
response = {'status' => 'success', 'data' => body}
format(status, headers, response)
rescue ::Exception => e
response = {'status' => 'error', 'message' => e.message}
format(500, {'Content-Type' => 'application/json'}, response)
end
end
def format(status, headers, response)
result = ActiveSupport::JSON.encode(response)
headers["Content-Length"] = result.length.to_s
[status, headers, result]
end
end
use ResponseMiddleware
run MyApp
Examples (in JSON):
/string
Expected: {"status":"success","data":"Hello World"}
Actual: {"status":"success","data":["Hello World"]}
/hash (works)
Expected: {"status":"success","data":{"person":{"name":"john","surname":"smith"}}}
Actual: {"status":"success","data":{"person":{"name":"john","surname":"smith"}}}
/array
Expected: {"status":"success","data": [1,2,3,4,5,6,7,"232323","3245235"]}
Actual: {"status":"error","message":"wrong number of arguments (7 for 1)"}
/object
Expected: {"status":"success","data":{"name":"simon","surname":"hernandez"}}
Actual: {"status":"success","data":[]}
/error (works)
Expected: {"status":"error","message":"Failure of some sort"}
Actual: {"status":"error","message":"Failure of some sort"}
If you execute the code, you will see that /hash and /error give back the required responses, but the rest do not. Ideally, I would not like to change anything in the MyApp class. It's currently being built on top of Sinatra 1.3.3, ActiveSupport 3.2.9 and Rack 1.4.1.

Answer 1

With some help from #sinatra on irc.freenode.org, I managed to get it down to what I want. I added the following to MyApp:
def route_eval
result = catch(:halt) { super }
throw :halt, {"result" => result}
end
I then changed the following line in ResponseMiddleware:
response = {'status' => 'success', 'data' => body}
to
response = {'status' => 'success', 'data' => body["result"]}
and all my test cases passed.