KMM: casting Kotlin's MutableMap to Swift

Question

I was able to retrieve a binding Swift Array from a Kotlin MutableList source,
but I can’t find the way to retrieve a binding Swift Array from a Kotlin MutableMap of MutableLists source, given the map key.

=====

Kotlin MutableList to binding Swift Array

Kotlin MutableList definition:

var path : MutableList<ScreenIdentifier> = mutableListOf()

retrieving Binding Swift Array => SUCCESSFUL!

extension Binding where Value == NSMutableArray {
    public func cast() -> Binding<[ScreenIdentifier]> {
        return Binding<[ScreenIdentifier]>(
            get:{ self.wrappedValue as NSArray as! [ScreenIdentifier] },
            set: { self.wrappedValue = NSMutableArray(array: $0) }
        )
    }
}
===
NavigationStack(path: $path.cast()) {
...
}
===

=====

Kotlin MutableMap of MutableList to binding Swift Array

Kotlin MutableMap of MutableLists definition:

var paths : MutableMap<String, MutableList<ScreenIdentifier>> = mutableMapOf()

retrieving Binding Swift Array => NOT WORKING

extension Binding where Value == NSMutableDictionary {
    public func getPath(level1URI: String) -> Binding<[ScreenIdentifier]> {
        return Binding<[ScreenIdentifier]>(
            get:{
                let dict = self.wrappedValue as NSDictionary as! [String:[ScreenIdentifier]]
                return dict[level1URI] as! NSMutableArray as NSArray as! [ScreenIdentifier]
            },
            set: {
                var modifiedDict = self.wrappedValue as! [NSString:NSMutableArray]
                modifiedDict[level1URI as NSString] = NSMutableArray(array: $0)
                self.wrappedValue = NSMutableDictionary(dictionary: modifiedDict as! KotlinMutableDictionary<NSString,NSMutableArray>)
            }
        )
    }
}
===
NavigationStack(path: $paths.getPath(level1URI: myString)) {
...
}
===

this is the error given by XCode:

Referencing instance method 'getPath(level1URI:)' on 'Binding' requires the types 'KotlinMutableDictionary<NSString, NSMutableArray>' and 'NSMutableDictionary' be equivalent

Answer 1

I found it!!!

On the Kotlin documentation, it's explained that Kotlin's MutableMap cannot cast directly to NSMutableDictionary, unlike MutableList which can instead cast directly to NSMutableArray.

So, the solution is to ignore NSMutableDictionary and to deal directly with KotlinMutableDictionary.

Here is the correct extension code:

extension Binding where Value == KotlinMutableDictionary<NSString,NSMutableArray> {
  public func getPath(level1URI: String) -> Binding<[ScreenIdentifier]> {
    return Binding<[ScreenIdentifier]>(
      get:{
        let dict = self.wrappedValue as! [String:[ScreenIdentifier]]
        return dict[level1URI]!
      },
      set: {
        var modifiedDict = self.wrappedValue as! [NSString:NSMutableArray]
        modifiedDict[level1URI as NSString] = NSMutableArray(array: $0)
        self.wrappedValue = KotlinMutableDictionary<NSString, NSMutableArray>.init(dictionary: modifiedDict)
      }
    )
  }
}