# subscript(_:) Accesses the particular container value associated with a custom key. ``` subscript(key: Key.Type) -> Key.Value where Key : ContainerValueKey { get set } ``` ## Overview Create a custom container value by declaring a new property in an extension to the container values structure and applying the [`Entry()`](/documentation/SwiftUI/Entry()) macro to the variable declaration: ``` extension ContainerValues { @Entry var myCustomValue: String = "Default value" } ``` You use custom container values the same way you use system-provided values, setting a value with the [`containerValue(_:_:)`](/documentation/SwiftUI/View/containerValue(_:_:)) view modifier, and reading values from a [`Subview`](/documentation/SwiftUI/Subview) provided by the `subviews` modifier. You can also provide a dedicated view modifier as a convenience for setting the value: ``` extension View { func myCustomValue(_ myCustomValue: String) -> some View { containerValue(\.myCustomValue, myCustomValue) } } ``` --- 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)