ValueObservationScheduler

public class ValueObservationScheduler

ValueObservationScheduler determines how ValueObservation notifies its fresh values.

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  • A scheduler which asynchronously notifies fresh value of the given DispatchQueue.

    For example:

    let observation = ValueObservation.tracking { db in
    try Player.fetchAll(db)
}

let cancellable = try observation.start(
    in: dbQueue,
    scheduling: .async(onQueue: .main),
    onError: { error in ... },
    onChange: { players: [Player] in
        print("fresh players: \(players)")
    })

    Declaration

    Swift

    public static func async(onQueue queue: DispatchQueue) -> ValueObservationScheduler
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  • A scheduler which notifies all values on the main queue. The first one is immediately notified when the start() method is called.

    For example:

    let observation = ValueObservation.tracking { db in
    try Player.fetchAll(db)
}

let cancellable = try observation.start(
    in: dbQueue,
    scheduling: .immediate,
    onError: { error in ... },
    onChange: { players: [Player] in
        print("fresh players: \(players)")
    })
// <- here "fresh players" is already printed.

    Important

    this scheduler requires that the observation is started from the main queue. A fatal error is raised otherwise.

    Declaration

    Swift

    public static let immediate: ValueObservationScheduler
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