Question

我正在尝试以下代码，但它引发了异常

content-div

它崩溃并显示以下错误

Error Domain = NSCocoaErrorDomain代码= 4865“没有与关联的值键CodingKeys（stringValue：“ lastName”，intValue：nil）（“ lastName”）。” UserInfo = {NSDebugDescription =没有与键关联的值 CodingKeys（stringValue：“ lastName”，intValue：nil）（“ lastName”）。， NSCodingPath =（）}

我知道JSON中缺少import Foundation class SomeBaseClass: Codable { let someInt: Int? let someString: String? init(someInt: Int,someString:String) { self.someInt = someInt self.someString = someString } init(someBaseClass: SomeBaseClass) { self.someString = someBaseClass.someString self.someInt = someBaseClass.someInt } } class Person: SomeBaseClass { let firstName: String? let lastName: String? init(firstName: String,lastName:String,someBaseClass: SomeBaseClass) { self.firstName = firstName self.lastName = lastName super.init(someBaseClass: someBaseClass) } enum CodingKeys: String, CodingKey { case firstName,lastName } required init(from decoder: Decoder) throws { let container = try decoder.container(keyedBy: CodingKeys.self) firstName = try container.decode(String.self, forKey: .firstName) lastName = try container.decode(String.self, forKey: .lastName) try super.init(from: container.superDecoder()) } } let json = """ { "firstName":"John", "someInt":2 } """ let jsonData = json.data(using: .utf8)! do { let personObject = try JSONDecoder().decode(Person.self, from: jsonData) dump(personObject) } catch let error as NSError { print(error) }，并且已将其标记为可选项，但它不能像它对结构的工作方式一样

有没有一种简单的方法可以做到这一点？

Answer 1

您应该使用decodeIfPresent作为可选属性

required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    firstName = try container.decodeIfPresent(String.self, forKey: .firstName)
    lastName = try container.decodeIfPresent(String.self, forKey: .lastName)

    try super.init(from: decoder)
}

还请注意将super更改为避免另一个错误所需的更改。您也可以从

稍微更改捕获量

} catch let error as NSError {
    print(error)
}

简单地

} catch {
    print(error)
}

具有继承的类可编码

1 个答案: