# attributedTextFormattingDefinition(_:) Apply a text formatting definition to nested views. ``` nonisolated func attributedTextFormattingDefinition(_ definition: D) -> some View where D : AttributedTextFormattingDefinition ``` ## Discussion Applying a text formatting definition to a `Text` or `TextEditor` created using the `Text/init(_:)-(AttributedString)` or `TextEditor/init(text:selection:)` initializer, respectively, makes sure that any content observable to the user adheres to the constraints of the formatting definition. You can compose your own definition from an attribute scope and a series of `AttributedTextValueConstraint`s: ``` // MyTextFormattingDefinition.swift struct MyTextFormattingDefinition: AttributedTextFormattingDefinition { var body: some AttributedTextFormattingDefinition< AttributeScopes.SwiftUIAttributes > { ValueConstraint( for: \.underlineStyle, values: [nil, .single], default: .single) MyAttributedTextValueConstraint() } } // MyEditorView.swift TextEditor(text: $text) .attributedTextFormattingDefinition(MyTextFormattingDefinition()) ``` > Note: A ``Binding`` to the text of a view with an > ``AttributedTextFormattingDefinition`` may still contain values that do > not adhere to text formatting definition. E.g., a ``TextEditor`` may > choose to not apply constraints in the text formatting definition to > parts of a bound attributed string that are not visible on screen. To manually enforce constraints, e.g. before serializing text contents, use the `AttributedTextFormattingDefinition/constrain(_:)-(AttributedString)` method. --- 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)