Subscribe to storage map Entries?

Question

On our substrate node using a storage double map. We are trying to subscribe to an entries query. something like

const unsub = await api.query.system.balances.entries(ADDR, (res) => {
  console.log(res);
});

It works and gets the entries on the first call but it is not updating / running the callback when the storageMap is updated. is it not possible to subscribe to the entries of a storage map?

Answer 1

The code you referenced does not work for me. I get the following error:

  await api.query.system.balances.entries(ADDR, (res) => {
                                  ^
TypeError: Cannot read properties of undefined (reading 'entries')

You have the correct format for entries. For example:

const referenda = await api.query.referenda.referendumInfoFor.entries();
referenda.forEach(async (referendum) => {
    if (referendum[1].toHuman()['Ongoing']) {
        const referendumIndex = referendum[0].args[0].toNumber();
        console.log("Referendum:", referendumIndex);
        console.log(referendum[1].toJSON());
    }
});

Depending on your chain, the balances of your accounts are actually stored in FRAME system pallet.

Perhaps this is what you are trying to achieve:

import { ApiPromise, WsProvider } from "@polkadot/api";

export const subscribeBalances = async () => {
  const provider = new WsProvider(ENDPOINT);
  const api = await ApiPromise.create({ provider });

  api.query.system.account(ADDR, (balance) => {
    console.log(`Balance for account ${account}: ${balance.data.free}`);
  });
};

Or depending on what you're trying to achieve you can also listen for events from the balances pallet. For example:

• https://polkadot.js.org/docs/substrate/events#transferaccountid32-accountid32-u128