add swiftUI code

iOS-SwiftUI-Code/GRDB.swift-6.29.3/Documentation/Playgrounds/TransactionObserver.playground/Contents.swift

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+//: To run this playground:
+//:
+//: - Open GRDB.xcworkspace
+//: - Select the GRDB scheme: menu Product > Scheme > GRDB
+//: - Build: menu Product > Build
+//: - Select the playground in the Playgrounds Group
+//: - Run the playground
+
+import GRDB
+
+
+// Create the database
+
+let dbQueue = try DatabaseQueue()   // Memory database
+var migrator = DatabaseMigrator()
+migrator.registerMigration("createPerson") { db in
+    try db.create(table: "person") { t in
+        t.autoIncrementedPrimaryKey("id")
+        t.column("name", .text).notNull()
+    }
+}
+migrator.registerMigration("createPet") { db in
+    try db.create(table: "pet") { t in
+        t.autoIncrementedPrimaryKey("id")
+        t.column("name", .text).notNull()
+        t.belongsTo("owner", inTable: "person", onDelete: .cascade)
+    }
+}
+try! migrator.migrate(dbQueue)
+
+
+//
+
+class TableChangeObserver : NSObject, TransactionObserver {
+    private var changedTableNames: Set<String> = []
+    
+    func observes(eventsOfKind eventKind: DatabaseEventKind) -> Bool { true }
+    
+    func databaseDidChange(with event: DatabaseEvent) {
+        changedTableNames.insert(event.tableName)
+    }
+    
+    func databaseDidCommit(_ db: Database) {
+        print("Changed table(s): \(changedTableNames.joined(separator: ", "))")
+        changedTableNames = []
+    }
+    
+    func databaseDidRollback(_ db: Database) {
+        changedTableNames = []
+    }
+}
+
+let observer = TableChangeObserver()
+dbQueue.add(transactionObserver: observer)
+
+
+//
+
+print("-- Changes without transaction")
+try dbQueue.inDatabase { db in
+    try db.execute(sql: "INSERT INTO person (name) VALUES (?)", arguments: ["Arthur"])
+    let arthurId = db.lastInsertedRowID
+    try db.execute(sql: "INSERT INTO person (name) VALUES (?)", arguments: ["Barbara"])
+    try db.execute(sql: "INSERT INTO pet (ownerId, name) VALUES (?, ?)", arguments: [arthurId, "Barbara"])
+    try db.execute(sql: "DELETE FROM person WHERE id = ?", arguments: [arthurId])
+}
+
+print("-- Rollbacked changes")
+try dbQueue.inTransaction { db in
+    try db.execute(sql: "INSERT INTO person (name) VALUES ('Arthur')")
+    try db.execute(sql: "INSERT INTO person (name) VALUES ('Barbara')")
+    return .rollback
+}
+
+
+print("-- Changes wrapped in a transaction")
+try dbQueue.write { db in
+    try db.execute(sql: "DELETE FROM person")
+    try db.execute(sql: "INSERT INTO person (name) VALUES (?)", arguments: ["Arthur"])
+    let arthurId = db.lastInsertedRowID
+    try db.execute(sql: "INSERT INTO person (name) VALUES (?)", arguments: ["Barbara"])
+    try db.execute(sql: "INSERT INTO pet (ownerId, name) VALUES (?, ?)", arguments: [arthurId, "Barbara"])
+    try db.execute(sql: "DELETE FROM person WHERE id = ?", arguments: [arthurId])
+}

iOS-SwiftUI-Code/GRDB.swift-6.29.3/Documentation/Playgrounds/TransactionObserver.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='osx' display-mode='rendered' buildActiveScheme='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>