Frozen Nodes

Frozen nodes in mobx-bonsai guarantee immutability. When a node type is created with the .frozen() modifier:

• Its properties become read-only (although only enforced in dev mode).
• It is kept as a plain JavaScript value with no MobX observability (so no conversion into nodes is needed for inner values).
• Snapshots of a frozen node are exactly the same as the node itself.

The example below demonstrates how a frozen node behaves.

import { nodeType, node, applySnapshot, getSnapshot } from "mobx-bonsai";

type FrozenPerson = TNode<"FrozenPerson",{
  name: string;
  hobbies: string[];
}>;

const TFrozenPerson = nodeType<FrozenPerson>("FrozenPerson").frozen();

// create a frozen node instance
const frozenPerson = TFrozenPerson({ name: "Alice", hobbies: ["cycling", "painting"] });

// attempting to change a property results in an error (in dev mode)
// frozenPerson.hobbies.push("singing");

// snapshots return the same object reference
console.log(getSnapshot(frozenPerson) === frozenPerson); // true

// frozen node used inside another node retains its reference
const parent = node({ person: frozenPerson });
console.log(parent.person === frozenPerson); // true