Dictionary of Dictionaries of Dictionaries of Dictionaries syntax understanding - ios

Question

I need to map the doors of buildings into a single map, from which afterward I need to populate three pickers using this data.
Each door contains the following data: building, level, range, door number and other information that is less relevant. So I created the following map:
public var doorsMap: [String : [String : [String : [String: Door]]]] = [:]
and a have a list of doors that I need to populate this map with, the problem is that I can't understand what should be the right syntax to perform this task, I tried:
doorsMap[door.building]?[door.level]?[door.range]?[door.number] = door
but this doesn't create the inner sets of dictionaries. when I tried to do:
doorsMap[door.building]![door.level]![door.range]![door.number] = door
Obviously, I get the:
Fatal error: Unexpectedly found nil while unwrapping an Optional value
because I try to unwrap a nil value.
So what would be the correct syntax in swift to populate this map from a list of doors?

Answer 1

A single assignment won't create the multiple, intermediate directories. You need to do it explicitly.
You could use something like this:
func add(door: Door) {
var building = self.doorsMap[door.building] ?? [String : [String:[String: Door]]]()
var level = building[door.level] ?? [String : [String: Door]]()
var range = level[door.range] ?? [String:Door]
range[door.number] = door
level[door.range] = range
building[door.level] = level
self.doorsMap[door.building] = building
}
Personally, I would look for a better data structure, perhaps use a struct to hold the doorsMap. This struct could have functions to handle the insertion and retrieval of doors.
Perhaps something like this:
struct Door {
let building: String
let level: String
let range: String
let number: String
}
struct DoorMap {
private var buildingsSet = Set<String>()
private var levelsSet = Set<String>()
private var rangesSet = Set<String>()
private var numberSet = Set<String>()
private var doorsArray = [Door]()
var buildings: [String] {
get {
return Array(buildingsSet).sorted()
}
}
var levels: [String] {
get {
return Array(levelsSet).sorted()
}
}
var ranges: [String] {
get {
return Array(rangesSet).sorted()
}
}
var numbers: [String] {
get {
return Array(numberSet).sorted()
}
}
var doors: [Door] {
get {
return doorsArray
}
}
mutating func add(door: Door) {
buildingsSet.insert(door.building)
levelsSet.insert(door.level)
rangesSet.insert(door.range)
numberSet.insert(door.number)
doorsArray.append(door)
}
func doorsMatching(building: String? = nil, level: String? = nil, range: String? = nil, number: String? = nil) -> [Door]{
let matches = doorsArray.filter { (potentialDoor) -> Bool in
var included = true
if let b = building {
if potentialDoor.building != b {
included = false
}
}
if let l = level {
if potentialDoor.level != l {
included = false
}
}
if let r = range {
if potentialDoor.range != r {
included = false
}
}
if let n = number {
if potentialDoor.number != n {
included = false
}
}
return included
}
return matches
}
}
var map = DoorMap()
let d1 = Door(building: "b1", level: "1", range: "r1", number: "1")
let d2 = Door(building: "b1", level: "2", range: "r1", number: "2")
let d3 = Door(building: "b2", level: "2", range: "r1", number: "2")
map.add(door: d1)
map.add(door: d2)
map.add(door: d3)
let b1Doors = map.doorsMatching(building:"b1")
let level2Doors = map.doorsMatching(level:"2")
let allBuildings = map.buildings()
Now, maybe you have more information on buildings and levels etc, so they could be structs too instead of just strings.