UUVPN/iOS-SwiftUI-Code/GRDB.swift-6.29.3/GRDB/Documentation.docc/DatabaseObservation.md

Database Observation

Observe database changes and transactions.

Overview

SQLite notifies its host application of changes performed to the database, as well of transaction commits and rollbacks.

GRDB puts this SQLite feature to some good use, and lets you observe the database in various ways:

• ValueObservation: Get notified when database values change.
• DatabaseRegionObservation: Get notified when a transaction impacts a database region.
• Database/afterNextTransaction(onCommit:onRollback:): Handle transactions commits or rollbacks, one by one.
• TransactionObserver: The low-level protocol that supports all database observation features.

Topics

Observing Database Values

• ValueObservation
• SharedValueObservation
• AsyncValueObservation
• Database/registerAccess(to:)

Observing Database Transactions

• DatabaseRegionObservation
• Database/afterNextTransaction(onCommit:onRollback:)

Low-Level Transaction Observers

• TransactionObserver
• Database/add(transactionObserver:extent:)
• Database/remove(transactionObserver:)
• DatabaseWriter/add(transactionObserver:extent:)
• DatabaseWriter/remove(transactionObserver:)
• Database/TransactionObservationExtent

Database Regions

• DatabaseRegion
• DatabaseRegionConvertible