Reflection in Swift using Mirror

Posted on Edited on Disqus: Word count in article: 1.6k Reading time ≈ 1 mins.

  • Mirror

    • value: Access the raw reflection value, but its type is Any.
    • valueType: The type of the raw reflection value, equivalent to value.dynamicType.

  • I didn’t find any way to assign $0.value with a pure Swift object, so Class inherits NSObject for KVC.

  • I ignored the simplified optional cases.

  • Recursively generate a dictionary or object.

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import Foundation

typealias DynamicKVType = [String: Any]
protocol DynamicKV {
    func dict() -> DynamicKVType
    func assignment(_ with: DynamicKVType)
}
extension DynamicKV {
    func dict() -> DynamicKVType {
        var dict = DynamicKVType()

        Mirror(reflecting: self).children.forEach {
            guard let k = $0.label else { return }
            if let v = $0.value as? DynamicKV {
                dict[k] = v.dict()
            } else {
                dict[k] = $0.value
            }
        }
        return dict
    }

    func assignment(_ with: DynamicKVType) {
        Mirror(reflecting: self).children.forEach {
            guard let obj = self as? NSObject, let dictV = with[$0.label!], let k = $0.label else { fatalError("child leak") }

            if let dkvt = dictV as? DynamicKVType, let v = $0.value as? DynamicKV {
                v.assignment(dkvt)
            } else {
                obj.setValue(dictV, forKey: k)
            }
        }
    }

}

class A: NSObject, DynamicKV {
    var s: String = "a"
    var i: Int = -1
}

class B: NSObject, DynamicKV {
    var s = "b"
    var a = A()
    var array = [0, 1, 2, 3]
}

let b = B()
print("b.dict\t", b.dict())

b.assignment(["s": "bbbbbbb", "a": ["s": "aaaaaaa", "i": 233], "array": [-3, -2, -1]])
print("b.assignment\t", b.s, b.a.s, b.a.i, b.array)

Translated by gpt-3.5-turbo