我有一个旧项目，我正试图从Swift 3移植到Swift 4再移植到Swift5。看来我最终需要离开ObjectMapper，但是在我能够这样做之前，我需要将这个错误修复为获取重新编译的代码。不幸的是，这只是整个代码库中此问题的众多实例之一，因此我无法避免。

代码let sortedWorkoutDiary = List(from: exercise.workoutDiary.sorted(byKeyPath: "date"))产生Argument type 'Results<Workout>' does not conform to expected type 'Decoder'错误：

    func recordWorkout(_ newWorkout: Workout) {
        let lastWorkout = exercise.workoutDiary.last // grab the last workout for later comparison

        let realm = try! Realm()
        try! realm.write {
            exercise.workoutDiary.append(newWorkout) // write the workout no matter what
        }

        if let secondToLastWorkout = lastWorkout { // only bother checking out of order if there is a last workout...
            if newWorkout.date < secondToLastWorkout.date { // ...and now look to see if they are out of order
                let sortedWorkoutDiary = List(from: exercise.workoutDiary.sorted(byKeyPath: "date")) // ERROR: Argument type 'Results<Workout>' does not conform to expected type 'Decoder'
                try! realm.write {
                    exercise.workoutDiary.removeAll()
                    exercise.workoutDiary.append(objectsIn: sortedWorkoutDiary)
                }
            }
        }
    }

这是将Realm List 支持添加到ObjectMapper的代码

class ListTransform<T:RealmSwift.Object> : TransformType where T:Mappable {

    typealias Object = List<T>
    typealias JSON = [[String:Any]]

    let mapper = Mapper<T>()

    func transformFromJSON(_ value: Any?) -> List<T>? {
        let result = List<T>()
        if let tempArr = value as? [Any] {
            for entry in tempArr {
                let mapper = Mapper<T>()
                let model : T = mapper.map(JSONObject: entry)!
                result.append(model)
            }
        }
        return result
    }

    func transformToJSON(_ value: Object?) -> JSON? {
        var results = [[String:Any]]()
        if let value = value {
            for obj in value {
                let json = mapper.toJSON(obj)
                results.append(json)
            }
        }
        return results
    }
}

对象的简化视图：

final class Exercise: Object,Mappable {

    dynamic var name = ""
    dynamic var notes: String?
    var workoutDiary = List<Workout>()
    dynamic var goal = 0

}

extension Exercise {

    func mapping(map: Map) {
        id <- map["id"]
        name <- map["name"]
        notes <- map["notes"]
        workoutDiary <- (map["workoutDiary"],ListTransform<Workout>())
        bodyWeightMultiplier <- map["bodyWeightMultiplier"]
        sortOrder <- map["sortOrder"]
        username <- map["username"]
    }

}

final class Workout: Object,Mappable {

    dynamic var date = NSDate()
    var sets = List<WorkSet>()

}

extension Workout {

    func mapping(map: Map) {
        date <- (map["date"],DateTransform())
        sets <- (map["sets"],ListTransform<WorkSet>())
    }

}