Styjun

I have nested dictionary, so something like this:

var dict = ["a":["b":"c", "d":["e":"f"]], "f":["b":"g"]] // and more

Now if I want to update the value of key a.d.e, how should I do that?

It seems updateValue method only reads key as it is...It doesn't know anything about the nested key.

Edit:

While I really want to change the structure of this data to something easier to work with. I can't. This belongs to another class and I am not allow to change the structure, all I can do is to update it.

Second Edit:

After some thoughts and read the other question some one point out might be a duplicate, tried recursively updating. I feel this is seriously the worst way to do it because essentially it's creating new dictionaries with a copy of original value and assign it back. I do think it is a waste of space and tbh even recursively calling this I feel is unnecessary.

func updateKey(key:[AnyHashable],val:Bool,data:[AnyHashable:Any])->[AnyHashable:Any]
var keyTemp = key
var tempData = data

if(keyTemp.count==1)
 tempData.updateValue(val, forKey: key[0])
 print(tempData)
 return tempData

else
 var firstLayerValue = data[keyTemp[0]] as? [AnyHashable:Any]
 var firstKey = keyTemp.removeFirst()
 var tempResult = updateKey(key: keyTemp, val: val, data: firstLayerValue!)
 tempData.updateValue(tempResult, forKey: firstKey)
 return tempData;
 

This returns a copy of what I intend to do, and I have to actually assign it back to the original copy. I really don't like this assigning back and forth thing, what if something went wrong in the middle then I might just end up losing the originally correct data.

Is there any better solution?

Another way of doing it

dict["a"]?["d"] = ["e": 123]
print(dict)

Outputs

["f": ["b": "g"], "a": ["b": "c", "d": ["e": 123]]]

Structs are the way to go. But if you really have to use dictionaries, here is a workaround:

var dict: [AnyHashable: Any] =
 ["a": ["b": "c", "d": ["e":"f"]],
 "f": ["b": "g"]]

let newValue = true

if var firstLevel = dict["a"] as? [String : Any],
 var secondLevel = firstLevel["d"] as? [String: Any] 
 secondLevel["e"] = newValue
 firstLevel["d"] = secondLevel
 dict["a"] = firstLevel


print(dict) //[AnyHashable("a"): ["d": ["e": true], "b": "c"], AnyHashable("f"): ["b": "g"]]

To update a value in a dictionary with multiple levels, you can define a function like so:

func update(dictionary dict: inout [AnyHashable: Any], at keys: [AnyHashable], with value: Any) 

 if keys.count < 2 
 for key in keys dict[key] = value 
 return
 

 var levels: [[AnyHashable: Any]] = []

 for key in keys.dropLast() 
 if let lastLevel = levels.last 
 if let currentLevel = lastLevel[key] as? [AnyHashable: Any] 
 levels.append(currentLevel)
 
 else if lastLevel[key] != nil, levels.count + 1 != keys.count 
 break
 else return 
 else 
 if let firstLevel = dict[keys[0]] as? [AnyHashable : Any] 
 levels.append(firstLevel )
 
 else return 
 
 

 if levels[levels.indices.last!][keys.last!] != nil 
 levels[levels.indices.last!][keys.last!] = value
 else return 

 for index in levels.indices.dropLast().reversed() 
 levels[index][keys[index + 1]] = levels[index + 1]
 

 dict[keys[0]] = levels[0]

And use it like so:

var dict: [AnyHashable: Any] = ["a": ["b": 1,
 "c": ["d": ["e": "f"],
 "g": ["h": 1.5]]],
 "j": ["k": 2]]

update(dictionary: &dict,
 at: ["a", "c", "d", "e"],
 with: true)

dict.forEach print($0) 

Here is the output in the console:

(key: AnyHashable("a"), value: [AnyHashable("b"): 1, AnyHashable("c"): [AnyHashable("d"): [AnyHashable("e"): true], AnyHashable("g"): ["h": 1.5]]])
(key: AnyHashable("j"), value: ["k": 2])