Migrating from v1 to v2 ​

The class name and import type has been changed ​

The library was created in 2017, long ago before Records & Tuples proposal was created. The fact this proposal is moving towards being a part of the language means "Record" as a term gains very particular meaning for the ecosystem. Besides, Immutable.Record and TypeScript's Record could potentially create confusion as well. Thus, the abstract class Record has been renamed to Data.

Dataclass v1 exposed a single default export which seemed to work just fine for most of the cases. However, it can create additional burden for CommonJS code and require some unnecessary tricks from the bundlers. Thus, Dataclass v2 uses named export.

-import Record from "dataclass";
+import { Data } from "dataclass";

Drop TypeScript generic from class definitions ​

Dataclass v1 required TypeScript classes to be generic due to polymorphic this for static members issue. The issue has not been resolved but in Dataclass v2 there was a change in typings that helped avoiding the issue in the first place. Now, the user's classes don't need to be generic.

-class User extends Record<User> {
+class User extends Data {
  name: string = "Anon";
}

Use static method create() instead of new operator ​

Dataclass v2 uses new implementation for class instantiation due to some browser incompatibilities.

-let user = new User({ name: "Ann" });
+let user = User.create({ name: "Ann" });

Moving to dataclass v2 will make use of new operator throwing runtime errors, suggesting to use static create() method instead.

Ensure no mutations happening in the code ​

While instance of data classes treated as immutable, the implementation still uses some safety precautions to ensure no mutations (accidental or intentional) can be made. In v1, when a prop is mutated, nothing happens, the value remains the same. The operation is basically ignored.

let user = new User({ age: 18 });

user.age = 100;

console.log(user.age);
// > 18

In v2, however, some additional precautions were made, to ensure that developers can spot bad code and mistakes. Mutating a property will now throw an error:

let user = new User({ age: 18 });

user.age = 100;
// Uncaught TypeError: "age" is read-only

This error comes from the use of Object.freeze() which throws an error when there was an attempt to mutate an existing property and when the user tries to add new property to the object.

Make sure the dependency is transpiled, if necessary ​

See Installation Guide & Troubleshooting for more details.