CODEWITHSUNDEEP
kotlin
Pin
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Reputation: 4016

Can Delegates.observable() be serializable?

Given a class

class Pizza(name: String?) : Serializable {
    var name: String? by Delegates.observable(name, {_,_,_ -> })
}

Why is this not serializable? It crashes with

Caused by: java.io.NotSerializableException: com.xxx.xxx.Pizza$$special$$inlined$observable$1

Upvotes: 1

Views: 470

Answers (1)

glee8e
glee8e

Reputation: 6419

The reason behind your issue is the delegates are stored as an array in a synthetic backing field which is neither marked as transient nor serialziable, so it prevents the serialization. However just marking the property with @Transient will probably ruin your serialized form. And may not work at all

Before JetBrains decide to make a final resolution to this issue, you should use writeReplace and readResolve to override the default serializing mechanism. I've provided a sample solution below:

class Pizza(name: String?) : Serializable {
    @Transient var name: String? by Delegates.observable(name)
    private fun writeReplace(stream: ObjectOutputStream): Object = SerialProxy(name)
    private class SerialProxy(var name: String): Serializable {
        private fun readResolve(): Object = Pizza(name)
    }
}

readObject()/writeObject() doesn't work because you have no way to set the delegate after constructor is invoked without using reflection.

Upvotes: 2

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