为什么#Codable#在下面的代码中不起作用? [英] Why #Codable# not working in below code?

问题描述

我有以下代码来测试Codable协议和JSONDecoder.

I have below code to test Codable protocol and JSONDecoder.

import UIKit

class ClassA: Codable {
    var age: Int = 1
}

class ClassB: Codable {
    var ageInfo: ClassA?
    var name: String
}

let json4 = """
{
    "ageInfo": {},
    "name": "Jack"
}
""".data(using: .utf8)!

do {
    let d = try JSONDecoder().decode(ClassB.self, from: json4)
} catch let err {
    print(err)
}

我的问题是，为什么 json4 无法解码?或如何解码 json4 ?

My question is, why json4 can't be decode? or how I can decode json4?

推荐答案

您的ClassB具有此功能:

Your ClassB has this:

var ageInfo: ClassA?

但这不能帮助您使用此JSON:

But that doesn’t help you with this JSON:

"ageInfo": {}

问题是ageInfo存在 ，但它也是空词典.因此，有 个ClassA，但它与您对ClassA的定义不符！

The problem is that ageInfo is present but it is also an empty dictionary. So there is a ClassA but it doesn't correspond to your definition of ClassA!

更改

class ClassA: Codable {
    var age: Int = 1
}

到

class ClassA: Codable {
    var age: Int? = 1
}

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