如何使用 Swift iOS 中的 Struct Modal class 中的虚拟值创建数组

Question

I am getting a JSON from my server. To parse the JSON, I am using Decoder and converting the data in my Modal Class object.

This is my Modal class for Decoder:

struct SyncModelRecord : Codable {

    var date : String
    var shakeState : Int
}

class SyncModel {

    var date : Date
    var shakeState : Int

    init?(record: SyncModelRecord) {

        guard let secondsFrom1970 = Double(record.date) else {
            return nil
        }

        date = Date(timeIntervalSince1970: secondsFrom1970)

        shakeState = record.shakeState
    }
}

My parsing is working fine.

My problem is that now I have to make a 'SyncModelRecord' dummy array like:

var dummySyncModelRecordArray = [SyncModelRecord]()

var syncModelRecord : SyncModelRecord?
syncModelRecord?.shakeState = 0
syncModelRecord?.date = String(Int64(syncTimestamp!))

dummySyncModelRecordArray.append(syncModelRecord!)

But this is not working. Its crashing with Error (Please see the below attached error screenshot).

Please advise me.

Answer 1

You're force unwrapping a value that is nil syncModelRecord .

You need to instantiate it when declaring it.

var syncModelRecord: SyncModelRecord? = SyncModelRecord()

Or, even better, don't declare it as an optional, since you know at that point that it will not be nil (if instantiated correctly, of course):

var syncModelRecord = SyncModelRecord()

Answer 2

You need to actually initialize syncModelRecord . Try this:

let syncModelRecord = SyncModelRecord(date: String(Int64(syncTimestamp!)), shakeState: 0)

dummySyncModelRecordArray.append(syncModelRecord!)

Another tip maybe worth exploring, you can directly decode a date and specify the decoder's strategy for it (in your case secondsSince1970 )