# TransactionKey A key for accessing values in a transaction. ``` protocol TransactionKey ``` ## Overview You can create custom transaction values by extending the [`Transaction`](/documentation/SwiftUI/Transaction) structure with new properties. First declare a new transaction key type and specify a value for the required [`defaultValue`](/documentation/SwiftUI/TransactionKey/defaultValue) property: ``` private struct MyTransactionKey: TransactionKey { static let defaultValue = false } ``` The Swift compiler automatically infers the associated [`Value`](/documentation/SwiftUI/TransactionKey/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 [`transaction(_:)`](/documentation/SwiftUI/View/transaction(_:)) view modifier: ``` MyView() .transaction { transaction in if transaction.myCustomValue { transaction.animation = .default.repeatCount(3) } } ``` ## Topics ### Setting a default value [`defaultValue`](/documentation/SwiftUI/TransactionKey/defaultValue) The default value for the transaction key. [`Value`](/documentation/SwiftUI/TransactionKey/Value) The associated type representing the type of the transaction key’s value. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)