CODEWITHSUNDEEP
iosswiftcodable
user121095
user121095

Reputation: 813

Codable for class with Inheritance

I am trying the following code but it is throwing an exception

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)
}

It crashes with the following error

Error Domain=NSCocoaErrorDomain Code=4865 "No value associated with key CodingKeys(stringValue: "lastName", intValue: nil) ("lastName")." UserInfo={NSDebugDescription=No value associated with key CodingKeys(stringValue: "lastName", intValue: nil) ("lastName")., NSCodingPath=( )}

I know lastName is missing in the JSON and i have marked it as optional but it does not work like how it works for structs

Is there a simple method to do the same ?

Upvotes: 1

Views: 223

Answers (1)

Joakim Danielson
Joakim Danielson

Reputation: 51871

You should use decodeIfPresent for your optional properties 

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)
}

Also note the change to super that was needed to avoid another error. You can also change your catch slightly from

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

to simply 

} catch {
    print(error)
}

Upvotes: 2

Related Questions