コード可能なNSManagedObjectは、私は、このJSONをデコードしようとしているとき、私はこのエラーを取得decodeIfPresentデータ型

Question

に失敗：

[{ 
    "id": "76f22c25-cee7-4c7a-94fa-1fb85720f580", 
    "purchaseDate": "2012-04-05T19:03:43Z", 
    "title": "azare", 

}, { 
    "id": "9b4b9f7d-382f-4555-9eaa-97939b13633f", 
    "purchaseDate": "2012-04-05T19:02:46Z", 
    "title": "Chocolat", 

}, { 
    "id": "02a0aa06-2d0c-4ab9-aaaa-af7dee7b4845", 
    "purchaseDate": "2012-09-24T17:39:52Z", 
    "title": "Some thing", 
}] 

Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.typeMismatch(Swift.Double, Swift.DecodingError.Context(codingPath: [Foundation.(_JSONKey in _12768CA107A31EF2DCE034FD75B541C9)(stringValue: "Index 0", intValue: Optional(0)), MyApp.Purchase.CodingKeys.purchaseDate], debugDescription: "Expected to decode Double but found a string/data instead.", underlyingError: nil)): file /BuildRoot/Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-900.0.69.2/src/swift/stdlib/public/core/ErrorType.swift, line 181

My code: 

//Purchase+CoreDataClass.swift 
@objc(Purchase) 
public class Purchase: NSManagedObject, Codable { 

    enum CodingKeys: String, CodingKey { 
     case id 
     case title 
     case purchaseDate 
    } 

required convenience public init(from decoder: Decoder) throws { 

var context : NSManagedObjectContext = MyAppCoreDataManager.sharedInstance.persistentContainer.viewContext 
     guard let entity = NSEntityDescription.entity(forEntityName: "Purchase", in: context!) else { fatalError() } 

     self.init(entity: entity, insertInto: context!) 
     let container = try decoder.container(keyedBy: CodingKeys.self) 

     self.title = try container.decodeIfPresent(String.self, forKey: .title) 
     self.id = try container.decodeIfPresent(String.self, forKey: .id) 
     self.purchaseDate = try! container.decodeIfPresent(Date.self, forKey: .purchaseDate) 

    } 

    public func encode(to encoder: Encoder) throws { 
     var container = encoder.container(keyedBy: CodingKeys.self) 
     try container.encode(id, forKey: .id) 
     try container.encode(title, forKey: .title) 
try container.encode(purchaseDate, forKey: .purchaseDate) 
} 
} 

// Purchase+CoreDataProperties.swift 

extension Purchase { 

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Purchase> { 
     return NSFetchRequest<Purchase>(entityName: "Purchase") 
    } 


    @NSManaged public var id: String? 
    @NSManaged public var title: String? 
    @NSManaged public var purchaseDate: Date? 
} 

//CALL 

    let decoder = JSONDecoder() 

        decoder.dataDecodingStrategy = .base64 
        let purchases = try decoder.decode([Purchase].self, from: value) 

If i remove "purchaseDate" everything works correctly 

Answer 1

一般的な誤解があり、誤差は約DateないDataです

JSONデコーダがデフォルトでISO8601の日付をデコードしないため、エラーが発生します。デフォルトはTimeInterval aka Doubleです。

エラーメッセージが言っていることだ：それはあなたが.iso8601

decoder.dateDecodingStrategy = .iso8601 

にデコーダのDateDecodingStrategyを設定し、try!に感嘆符を削除する必要がDoubleを期待していますがString

を見つけましたエラーを引き継ぐ