in CoffeeScript, how can I use a variable as a key in a hash?

Question

eg:

So:

foo = \"asdf\"
{foo: \"bar\"}
eval foo

# how do I g         


        

Answer 1

If you're looking to use Coffeescript's minimal syntax for defining your associative array, I suggest creating a simple two line method to convert the variable name keys into the variable values after you've defined the array.

Here's how I do it (real array is much larger):

@sampleEvents = 
   session_started:
          K_TYPE: 'session_started'
          K_ACTIVITY_ID: 'activity'

   session_ended:
          K_TYPE: 'session_ended'

   question_answered:
          K_TYPE: 'question_answered'
          K_QUESTION: '1 + 3 = '
          K_STUDENT_A: '3'
          K_CORRECT_A: '4' #optional
          K_CORRECTNESS: 1 #optional
          K_SECONDS: 10 #optional
          K_DIFFICULTY: 4 #optional


for k, event of @sampleEvents
    for key, value of event
        delete event[key]
        event[eval(key.toString())] = value

The SampleEvents array is now:

{ session_started: 
   { t: 'session_started',
     aid: 'activity',
     time: 1347777946.554,
     sid: 1 },
  session_ended: 
   { t: 'session_ended', 
     time: 1347777946.554, 
     sid: 1 },
  question_answered: 
   { t: 'question_answered',
     q: '1 + 3 = ',
     sa: '3',
     ca: '4',
     c: 1,
     sec: 10,
     d: 4,
     time: 1347777946.554,
     sid: 1 },