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使用可选类型时的RealmSwift和Codable

codable realm swift3 swift

Nox · 技术社区 · 7 年前

RealmSwift 但是,我的api开发人员给了我两个新属性,它们只存在于对象的一些返回调用中。如果我打电话 getUserInfo ,我收到 user model 没有这两个属性。在这种情况下,可以在codable中使用decodeIfPresent并将数据类型设置为optional。然而,这两个字段是纪元时间值,使它们成为某种数字。领域要求数据类型以前缀 @objc .

@objc dynamic var scanIn:Double = 0

NONE 它们中的一个是可选的。你必须使用 NSNumber ObjC ,但幸运的是, Codable 不适用于

我试着设置一个值,如果没有返回,就使用一个非可选类型

scanIn = try container.decodeIfPresent(Double.self, forKey:.scanIn) ?? 0

但是,由于某些原因,这会将所有值设置为0。我不知道为什么它会这样做,但另一个开发人员建议它不能像那样在可编码的环境下工作,我不得不将double设置为optional。我想澄清一下,这个数字在转换之前就存在,但在转换之后是0。

有什么简单的解决办法吗?也许我做错了什么?

2 回复 | 直到 7 年前

Vin Gazoil 7 年前

你可以用 RealmOptional<Double> 键入。

documentation :

可选的数值类型使用 RealmOptional 类型:

let age = RealmOptional<Int>()

支架 Int , Float , Double Bool ,以及所有大小版本的 内景 Int8 , Int16 , Int32 Int64 ).

Nox 7 年前

文·加佐利给了我丢失的钥匙。

myObject.myVariable.value = newValue . 然后,无论您在哪里使用它,都必须将其用作obj.variable.value。realmopnational不符合codable,因此必须编写扩展。你可以在下面找到它以及我收到它的地方的链接。

对象的ex:

class Attendee: Object,Codable {

@objc dynamic var id = 0
@objc dynamic var attendeeId = 0
@objc dynamic var lanId = ""
@objc dynamic var firstName = ""
@objc dynamic var lastName = ""
@objc dynamic var email = ""
@objc dynamic var employeeId = ""
@objc dynamic var badgeId = ""
@objc dynamic var department = ""
@objc dynamic var picture:String? = nil
let scanIn = RealmOptional<Double>()
let scanOut = RealmOptional<Double>()

override static func primaryKey () -> String? {
    return  "id"
}

private enum CodingKeys: String, CodingKey {
    case id, attendeeId, lanId, firstName, lastName, email, employeeId, badgeId, department, picture, scanIn, scanOut
}

required convenience init(from decoder: Decoder) throws {
    self.init()
    let container = try decoder.container(keyedBy: CodingKeys.self)
    id = try container.decode(Int.self, forKey:.id)
    attendeeId = try container.decodeIfPresent(Int.self, forKey:.attendeeId) ?? 0
    lanId = try container.decode(String.self, forKey:.lanId)
    firstName = try container.decode(String.self, forKey:.firstName)
    lastName = try container.decode(String.self, forKey:.lastName)
    email = try container.decode(String.self, forKey:.email)
    employeeId = try container.decode(String.self, forKey:.employeeId)
    badgeId = try container.decode(String.self, forKey:.badgeId)
    department = try container.decode(String.self, forKey:.department)
    picture = try container.decodeIfPresent(String.self, forKey:.picture)
    self.scanIn.value = try container.decodeIfPresent(Double.self, forKey:.scanIn) ?? 0
    self.scanOut.value = try container.decodeIfPresent(Double.self, forKey:.scanOut) ?? 0
}

下面的代码是实现上述对象功能所必需的。恢复 from this link 与h1m5在该页评论中的修正一起。下面是双人间。链接有其他原语。

func assertTypeIsEncodable<T>(_ type: T.Type, in wrappingType: Any.Type) {
guard T.self is Encodable.Type else {
    if T.self == Encodable.self || T.self == Codable.self {
        preconditionFailure("\(wrappingType) does not conform to Encodable because Encodable does not conform to itself. You must use a concrete type to encode or decode.")
    } else {
        preconditionFailure("\(wrappingType) does not conform to Encodable because \(T.self) does not conform to Encodable.")
    }
}
}

func assertTypeIsDecodable<T>(_ type: T.Type, in wrappingType: Any.Type) {
guard T.self is Decodable.Type else {
    if T.self == Decodable.self || T.self == Codable.self {
        preconditionFailure("\(wrappingType) does not conform to Decodable because Decodable does not conform to itself. You must use a concrete type to encode or decode.")
    } else {
        preconditionFailure("\(wrappingType) does not conform to Decodable because \(T.self) does not conform to Decodable.")
    }
}
}

extension RealmOptional : Encodable where Value : Encodable {
public func encode(to encoder: Encoder) throws {
    assertTypeIsEncodable(Value.self, in: type(of: self))

    var container = encoder.singleValueContainer()
    if let v = self.value {
        try (v as Encodable).encode(to: encoder)  // swiftlint:disable:this force_cast
    } else {
        try container.encodeNil()
    }
}
}

extension RealmOptional : Decodable where Value : Decodable {
public convenience init(from decoder: Decoder) throws {
    // Initialize self here so we can get type(of: self).
    self.init()
    assertTypeIsDecodable(Value.self, in: type(of: self))

    let container = try decoder.singleValueContainer()
    if !container.decodeNil() {
        let metaType = (Value.self as Decodable.Type) // swiftlint:disable:this force_cast
        let element = try metaType.init(from: decoder)
        self.value = (element as! Value)  // swiftlint:disable:this force_cast
    }
}
}