Swift keyPath playground

TestSwiftKEyPatch.swift

import Cocoa

class AppData {
    var iDict1: [Int:Int] = [1:1, 2:2]
    var iDict2: [Int:Int] = [1:11, 2:22]
    
    var sDict1: [Int:String] = [1: "One", 2: "Two"]
    var sDict2: [Int:String] = [1: "One2", 2: "Two2"]
    
    static let propPath: [String: PartialKeyPath<AppData>] = [
        "iDict1": \AppData.iDict1,
        "iDict2": \AppData.iDict2,
        "sDict1": \AppData.sDict1,
        "sDict2": \AppData.sDict2
    ]
    
    func printAll() {
        for (key, path) in AppData.propPath {
            print(key, type(of: path).rootType, type(of: path).valueType)
            switch type(of: path).valueType {
            case is Dictionary<Int, Int>.Type:
                let iPath = path as! KeyPath<AppData, Dictionary<Int,Int>>
                self[keyPath: iPath].forEach{ print("\($0):\($1)") }
            case is Dictionary<Int, String>.Type:
                let iPath = path as! KeyPath<AppData, Dictionary<Int,String>>
                self[keyPath: iPath].forEach{ print("\($0):\($1)") }
            default:
                fatalError()
            }
        }
    }
    
    func modDict(dictName: String) {
        guard let path = AppData.propPath[dictName] else {
            return
        }
        switch type(of: path).valueType {
        case is Dictionary<Int, Int>.Type:
            let iPath = path as! ReferenceWritableKeyPath<AppData, Dictionary<Int,Int>>
            self[keyPath: iPath].keys.forEach{ self[keyPath: iPath][$0]? += 1000 }
        case is Dictionary<Int, String>.Type:
            let sPath = path as! ReferenceWritableKeyPath<AppData, Dictionary<Int,String>>
            self[keyPath: sPath].keys.forEach{ self[keyPath: sPath][$0]?.append("-----") }
        default:
            fatalError()
        }
    }
}

var appData = AppData()
print("Before:")
appData.printAll()
appData.modDict(dictName: "sDict1")
appData.modDict(dictName: "iDict2")
print("After:")
appData.printAll()