TimestampedRecord: an example protocol for GRDB records that track their creation and modification dates.

TimestampedRecord.swift

/// A type that tracks its creation and modification dates, as described in
/// <https://swiftpackageindex.com/groue/grdb.swift/documentation/grdb/recordtimestamps>
protocol TimestampedRecord {
    var creationDate: Date? { get set }
    var modificationDate: Date? { get set }
}

extension TimestampedRecord where Self: MutablePersistableRecord {
    /// Sets `modificationDate` to the transaction date.
    mutating func touch(_ db: Database) throws {
        modificationDate = try db.transactionDate
    }
    
    /// Sets both `creationDate` and `modificationDate` to the transaction date,
    /// if they are not set yet.
    ///
    /// Records that customize the `willInsert` callback can call this method
    /// from their implementation.
    mutating func initializeTimestamps(_ db: Database) throws {
        if creationDate == nil {
            creationDate = try db.transactionDate
        }
        if modificationDate == nil {
            modificationDate = try db.transactionDate
        }
    }
    
    // Default implementation of `willInsert`.
    mutating func willInsert(_ db: Database) throws {
        try initializeTimestamps(db)
    }
    
    /// Sets `modificationDate` to the transaction date, and executes an
    /// `UPDATE` statement on all columns.
    mutating func updateWithTimestamp(_ db: Database) throws {
        try touch(db)
        try update(db)
    }
}

// ======================
// DEMO

struct Player: Codable, MutablePersistableRecord, FetchableRecord, TimestampedRecord {
    var id: Int64?
    var creationDate: Date?
    var modificationDate: Date?
    var name: String
    var score: Int
    
    mutating func didInsert(_ inserted: InsertionSuccess) {
        id = inserted.rowID
    }
}

let dbQueue = try DatabaseQueue()
try dbQueue.write { db in
    try db.create(table: "player") { t in
        t.autoIncrementedPrimaryKey("id")
        t.column("creationDate", .datetime).notNull()
        t.column("modificationDate", .datetime).notNull()
        t.column("name", .text).notNull()
        t.column("score", .integer).notNull()
    }
}

try dbQueue.write { db in
    // Insertion sets the creation and modification dates
    var player = Player(name: "Arthur", score: 1000)
    try player.insert(db)
    assert(player.creationDate != nil)
    assert(player.modificationDate != nil)
    
    // Call updateWithTimestamp() instead of update() in order
    // to bump the modification date
    player.score += 1
    try player.updateWithTimestamp(db)
}