Type-safe CKRecord extension by Objective-C keyPath.

CKRecord+KeyPath.swift

extension CKRecord {
    public subscript<Root, Value: CKRecordValueProtocol>(keyPath keyPath: WritableKeyPath<Root, Value>) -> Value? {
        get {
            let key = NSExpression(forKeyPath: keyPath).keyPath
            return self[key]
        }
        set {
            let key = NSExpression(forKeyPath: keyPath).keyPath
            self[key] = newValue
        }
    }
}

Usage.swift

// need `@objc` to extract keyPath string with NSExpression
@objc protocol MyRecord {
    var aaa: Bool { get set }
    var bbb: String { get set }
}

func usage() {
    let record = CKRecord(recordType: "Test")
    record[keyPath: \MyRecord.aaa] = true

    let value = record[keyPath: \MyRecord.aaa]
    // type of `value` is `Bool?`
  
    print(value)
    // Optional(true)
}

This is more type-safe than below
https://gist.github.com/Koze/f6afb934377717bf34fd285439e86281