Question

以下是代码（主要是从http://codelle.com/blog/2016/5/an-easy-way-to-convert-swift-structs-to-json/复制而来）：

import Foundation

protocol JsonRepresentable {
    var JsonRepresentation: AnyObject {get}
}

protocol JsonSerializable: JsonRepresentable {
}

extension JsonSerializable {
    var JsonRepresentation: AnyObject {
        var representation = [String: AnyObject]()
        for case let (label?, value) in Mirror(reflecting: self).children {
            switch value {
            case let value as JsonRepresentable:
                representation[label] = value.JsonRepresentation
            case let value as NSNumber:
                representation[label] = value
            case let value as NSString:
                representation[label] = value
            case let value as NSArray:
                representation[label] = value
            case let value as NSDictionary:
                representation[label] = value
            case let value as NSNull:
                representation[label] = value
            default:
                break

            }
        }
        return representation as AnyObject
    }

    func toJson() -> String? {
        let representation = JsonRepresentation
        guard JSONSerialization.isValidJSONObject(representation) else {
            return nil
        }
        do {
            let data = try JSONSerialization.data(withJSONObject: representation, options: [])
            return String(data: data, encoding: String.Encoding.utf8)
        } catch {
            return nil
        }
    }
}

struct Owner: JsonSerializable {
    var name: String
}

struct Car: JsonSerializable {
    var manufacturer: String
    var model: String
    var mileage: Float
    var owner: Owner
}

let car = Car(manufacturer: "Kia", model: "K23", mileage: 143.3, owner: Owner(name: "娴静"))
print(car.toJson())

一切都按预期工作，我唯一的问题是NSString, NSNumber, NSArray等的分支是完全相同的。如何避免这种冗余？

Answer 1

而不是case let，您可以使用可级联的is

extension JsonSerializable {
    var JsonRepresentation: Any {
        var representation = [String: Any]()
        for case let (label?, value) in Mirror(reflecting: self).children {
            switch value {
            case let value as JsonRepresentable:
                representation[label] = value.JsonRepresentation
            case is NSNumber, is NSString, is NSArray, is NSDictionary, is NSNull: representation[label] = value
            default:
                break

            }
        }
        return representation as Any
    }

 ....

考虑到Swift 3中的JSON是Any

swift中有多个`case let`子句

1 个答案: