Using TypeScript to deserialize various types from a shared object

I am currently dealing with a JSON array containing serialized objects, each of which has a type field. My challenge lies in deserializing them properly due to TypeScript not cooperating as expected:

Check out the TypeScript playground for reference.

type serializedA = { type: 'A', aProp: string };
class A {
    public type = 'A';
    constructor(data: serializedA) {}
}

type serializedB = { type: 'B', bProp: string };
class B {
    public type = 'B'
    constructor(data: serializedB) {}
}

const classMap = { A, B };

function deserialize(serializedObject: serializedA | serializedB) {
    const Klass = classMap[serializedObject.type];
    new Klass(serializedObject);
}

The problem arises from the last line where TypeScript is unable to determine whether Klass and serializedObject are now both instances of A or B. I'm struggling to find a way to clarify this to TypeScript.

typescript

Answer №1

Looking for top-notch decoding libraries suitable for production use? Check out these recommendations:

We have been heavily relying on io-ts in our projects. For more information, you can find it here

Answer №2

interface SerializedData {
    type: string;
    prop: string;
}

class CustomClass {
    public type: string;
    constructor(data: SerializedData) {}
}

const classDictionary = { A: CustomClass, B: CustomClass };

function deserializeObject(serializedObj: SerializedData) {
    let Klass = classDictionary[serializedObj.type];
    return new Klass(serializedObj);
}

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