createCustomPersister
The createCustomPersister
function creates a Persister
object that you can configure to persist the Store
in any way you wish.
createCustomPersister<ListeningHandle>(
store: Store,
getPersisted: () => Promise<undefined | [Tables, Values]>,
setPersisted: (getContent: () => [Tables, Values], getTransactionChanges?: any) => Promise<void>,
addPersisterListener: (listener: PersisterListener) => ListeningHandle,
delPersisterListener: (listeningHandle: ListeningHandle) => void,
onIgnoredError?: (error: any) => void,
): Persister
Type | Description | |
---|---|---|
store | Store | The |
getPersisted | () => Promise<undefined | [Tables, Values]> | An asynchronous function which will fetch content from the persistence layer (or |
setPersisted | (getContent: () => [Tables, Values], getTransactionChanges?: any) => Promise<void> | An asynchronous function which will send content to the persistence layer. Since v4.0, it receives functions for getting the |
addPersisterListener | (listener: PersisterListener) => ListeningHandle | A function that will register a |
delPersisterListener | (listeningHandle: ListeningHandle) => void | A function that will unregister the listener from the underlying changes to the persistence layer. It receives whatever was returned from your |
onIgnoredError? | (error: any) => void | An optional handler for the errors that the |
returns | Persister | A reference to the new |
As well as providing a reference to the Store
to persist, you must provide functions that handle how to fetch, write, and listen to, the persistence layer.
The other creation functions (such as the createSessionPersister
function and createFilePersister
function, for example) all use this function under the covers. See those implementations for ideas on how to implement your own Persister
types.
This API changed in v4.0. Any custom persisters created on previous versions should be upgraded. Most notably, the setPersisted
function parameter is provided with a getContent
function to get the content from the Store
itself, rather than being passed pre-serialized JSON. It also receives information about the changes made during a transaction. The getPersisted
function must return the content (or nothing) rather than JSON. startListeningToPersisted
has been renamed addPersisterListener
, and stopListeningToPersisted
has been renamed delPersisterListener
.
Example
This example creates a custom Persister
object and persists the Store
to a local string called storeJson
and which would automatically load by polling for changes every second.
const store = createStore().setTables({pets: {fido: {species: 'dog'}}});
let storeJson;
const persister = createCustomPersister(
store,
async () => {
// getPersisted
return JSON.parse(storeJson);
},
async (getContent) => {
// setPersisted
storeJson = JSON.stringify(getContent());
},
(listener) => setInterval(listener, 1000),
(interval) => clearInterval(interval),
);
await persister.save();
console.log(storeJson);
// -> '[{"pets":{"fido":{"species":"dog"}}},{}]'
storeJson = '[{"pets":{"fido":{"species":"dog","color":"brown"}}},{}]';
await persister.load();
console.log(store.getTables());
// -> {pets: {fido: {species: 'dog', color: 'brown'}}}
persister.destroy();