Is something like this possible with serialization...

# serialization

[Joshua Hansen]

Is something like this possible with serialization? I'm just going to post the sample code here because it's quite a bit to explain. My goal is to ensure that any Child2 instances inside of Child1 instances are always ===. In some manner, I sort of want to deserialize all the Child2 instances and use their references as the deserialized input for the Child1 instances, and throw an exception if the serialized data doesn't conform.

fun main() {
    val test = Root()
    
    val child2 = Child2("Foo")
    val Child1 = Child1("Bar", child2)

    root.children1.add(child1)
    root.children2.add(children2)
    
    val jsonOutput = Json.encodeToString(test)
    
    val testInput = Json.decodeFromString<Root>(jsonOutput)
    
    /* Is it possible to make this true after deserialization? */
    testInput.children1.first().bar === testInput.children2.first()
}

@Serializable
class Root {
    val children1 = mutableListOf<Child1>()
    val children2 = mutableListOf<Child2>()
}

@Serializable
class Child1(
    val foo: String,
    val bar: Child2,
)

@Serializable
class Child2(val value: String)

[Joshua Hansen]

My current workaround is to just make Child1 store a string reference to `Child2`'s value and look up the instance at runtime.

[glureau]

Did you try to use value class for your Child2? I'd guess the === is forwarded to the String class, and as the JVM uses a String Constant Pool to not duplicate strings, it may work. But I won't feel very confident about it to be honest.

[glureau]

It's likely doable with a custom serializer if you have a pool of Child2 defined inside, which could create mem leaks tho.
(If it was my project, I'd challenge the use of '===' to start with.)