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Purpose of the Updater

The Updater is designed to handle data synchronization from the local Store to a remote data source. It provides:
  • Data Mutation Synchronization: Ensures that any changes made locally are propagated to the remote data source.
  • Completion Handling: Enables custom logic to be executed upon the completion of the network operation.

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APIs

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Updater

The Updater interface has the following structure: 
interface Updater<Key : Any, Output : Any, Response : Any> {
    suspend fun post(key: Key, value: Output): UpdaterResult
    val onCompletion: OnUpdaterCompletion<Response>?
}
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Key
Any
required
The type representing the key used to identify the data to fetch. For example, if fetching a list of posts, this could be an Int representing the post ID.
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Output
Any
required
The type representing the domain data model representation of the item being retrieved.
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Response
Any
required
The type representing the response received after updating the remote data source.

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post

Makes a network request to update the remote data source with the provided data.
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key
Key
required
The unique key identifying the data item.
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value
Output
required
The data to be written, in the domain model format.

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onCompletion

An optional callback executed upon the completion of the network operation.

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Data Flow

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Writing Data and Synchronization

When a data mutation occurs in the lcoal Store, the Updater is invoked to synchronize the change with the remote data source.
1

Local Mutation

A write request is made to the Store, updating the local data.
val writeRequest = StoreWriteRequest.of(key, value)
mutableStore.write(writeRequest)
2

Queue Write Request

The write request is added to a per-key write request queue in the RealMutableStore.
addWriteRequestToQueue(writeRequest)
3

Update Local Store

The RealMutableStore writes the new value to the local data source using a delegate RealStore.
delegate.write(writeRequest.key, writeRequest.value)
4

Attempt Server Synchronization

The Updater attempts to post the latest value to the remote data source.
val updaterResult = updater.post(writeRequest.key, writeRequest.value)
5

Handle Updater Result

NaN

Success

  • Updates the write request queue, removing processed requests.
  • Clears any failed sync records from the Bookkeeper.
  • Executes onCompletion callback if provided.
NaN

Failure

  • Records the failed attempt using the Bookkeeper.
  • Leaves the write request in the queue for future retries.
6

Emit Write Response

The RealMutableStore emits a StoreWriteResponse to consumers, indicating the success or failure of the write operation.
emit(storeWriteResponse)

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Best Practices

  • Handle Updater Results Appropriately: Use the onCompletion callback to perform actions based on success or failure.
  • Provide a Bookkeeper: The Bookkeeper is responsible for recording failed sync attempts, allowing the RealMutableStore to retry failed operations by invoking the Updater again.