ios - Dictionary inside dictionary -

i trying use list value dictionary key/pair set, , dictionary value in key/pair set in dictionary. explain, how initialize it.

var dictofevents = [int: [int: [pfobject]]]() 

i trying add events list, inner dictionary's key being day of month , outer 1 being month. example, event on may 1 be:

dictofevents[5:[1:[listofevents]] 

where listofevents array of pfobjects. before added month functionality, , outer dictionary, way added new events was: ` self.dictofevents[components.day] = [event] now, when try extend with:

self.dictofevents[components.month]?[components.day]! = [event] 

it not work. explanation on how create new event lists , access double layer dictionary appreciated.

(note: don't know put ! , ? in last piece of code please excuse me if made mistake.)

here think use of optionals in case (and should respond question):

var dic: [int: [int: [string]]] = [:] dic[5] = [1:["hello", "world"]]  if let list = dic[5]?[1] {     // list exist , can safely use     item in list {         println(item)     } } 

i used string instead of pfobject.

a different approach be:

/* define struct encapsulate month , day make hashable can use dictionary key */ public struct monthday: hashable {     let month: int     let day: int     public var hashvalue: int { return month * 100 + day } }  public func ==(lhs: monthday, rhs: monthday) -> bool {     return lhs.month == rhs.month && lhs.day == rhs.day }  var dictofevents = [monthday :[string]]() let amonthandday = monthday(month: 5, day: 1)  dictofevents[amonthandday] = ["hello", "world"] if let list = dictofevents[amonthandday] {     // list exist , can safely use     item in list {         println(item)     } }