# defaultValue The default value of the key. ``` static var defaultValue: Self.Value { get } ``` ## Discussion Implement the `defaultValue` property for a type that conforms to the [`LayoutValueKey`](/documentation/SwiftUI/LayoutValueKey) protocol. For example, you can create a `Flexibility` layout value that defaults to `nil`: ``` private struct Flexibility: LayoutValueKey { static let defaultValue: CGFloat? = nil } ``` The type that you declare for the `defaultValue` sets the layout key’s [`Value`](/documentation/SwiftUI/LayoutValueKey/Value) associated type. The Swift compiler infers the key’s associated type in the above example as an optional . Any view that you don’t explicitly set a value for uses the default value. Override the default value for a view using the [`layoutValue(key:value:)`](/documentation/SwiftUI/View/layoutValue(key:value:)) modifier. --- 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)