Mutate Exo Class Stete

README.md

Mutating Exo Class State

I'm confused about how to mutate the state of an exo class. The test above reproduces the prpblem I'm facing. The part that confuses me the most is that we're able to mutate the state object in contracts like vaultManager. The reason why I'm vaultManager confuses me is that zone API and prepareExoClassKit(what vaultManager uses) use the same code underneeth, as far as I know. Could use a clarification here.

test-mutateState.js

import { test } from '@agoric/zoe/tools/prepare-test-env-ava.js';
import { heapZone } from '@agoric/zone';

const prepareTestExo = zone => {
  const makeTestExo = zone.exoClass(
    'TestExo',
    undefined,
    () => {
      const wantToMutate = harden({
        a: '1',
        b: 2,
      });

      return harden({ wantToMutate });
    },
    {
      mutate(newVal) {
        const { state } = this;
        const { wantToMutate: oldVal } = state;

        state.wantToMutate = harden({
          ...oldVal,
          ...newVal,
        });
      },
      getState() {
        console.log('this', this);
        const { state } = this;
        return harden({ ...state });
      },
    },
  );

  return makeTestExo;
};

test('initial', t => {
  const makeTestExo = prepareTestExo(heapZone);
  const testExo = makeTestExo();
  const stateOne = testExo.getState();
  t.deepEqual(stateOne, {
    wantToMutate: {
      a: '1',
      b: 2,
    },
  });
  t.throws(() =>
    testExo.mutate({
      a: 4,
    }),
  );
  const stateTwo = testExo.getState();
  t.notDeepEqual(stateTwo, {
    wantToMutate: {
      a: 4,
      b: 2,
    },
  });
});