TransactionKey

protocol · iOS 17.0+ · SDK 27.1

protocol TransactionKey

A key for accessing values in a transaction. You can create custom transaction values by extending the ``Transaction`` structure with new properties. First declare a new transaction key type and specify a value for the required ``defaultValue`` property: private struct MyTransactionKey: TransactionKey { static let defaultValue = false } The Swift compiler automatically infers the associated ``Value`` type as the type you specify for the default value. Then use the key to define a new transaction value property: extension Transaction { var myCustomValue: Bool { get { self[MyTransactionKey.self] } set { self[MyTransactionKey.self] = newValue } } } Clients of your transaction value never use the key directly. Instead, they use the key path of your custom transaction value property. To set the transaction value for a change, wrap that change in a call to `withTransaction`: withTransaction(\.myCustomValue, true) { isActive.toggle() } To use the value from inside `MyView` or one of its descendants, use the ``View/transaction(_:)`` view modifier: MyView() .transaction { transaction in if transaction.myCustomValue { transaction.animation = .default.repeatCount(3) } }

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