Question

I have this class in which i try to initialize array attributes with query results:

class data
minute: []
hour:   []
constructor:    () ->
    findMin = events.find({"aggr":"minute"}).sort({$natural:-1}).limit(120)
    findHour = events.find({"aggr":"hour"}).sort({$natural:-1}).limit(14)
    findMin.execFind (errMin, resMin) ->
        for recMin in resMin
            @minute.push recMin
    findHour.execFind (errH, resH) ->
        for recH in resH
            @hour.push recH

So i call smth = new data() and console.log smth and get an empty attributes and an error about undefined not having ‘push’ method. While i can understand an error i cant get why my arrays are empty. Dont get me wrong – i know this error causes them to be empty, but i tried several kinds of variants. And ive read about acync and callbacks, but still don’t have a clue how to use callbacks not to ‘alert’ smth, but to use it afterwards. If you could help me with that or with some links that could – i would appreciate it SO much.

Answer 1

I assume you want minute and hour to be instance variables? They must be initialized in the constructor. The way you’re doing it now, they’re on the prototype, so it won’t work properly. Try this:

class data
  constructor:    () ->
    @minute = []
    @hour = []
    findMin = events.find({"aggr":"minute"}).sort({$natural:-1}).limit(120)
    findHour = events.find({"aggr":"hour"}).sort({$natural:-1}).limit(14)
    findMin.execFind (errMin, resMin) =>
        for recMin in resMin
            @minute.push recMin
    findHour.execFind (errH, resH) =>
        for recH in resH
            @hour.push recH