UIMutableTraits
A mutable container of traits.
Declaration
protocol UIMutableTraitsOverview
The UIMutableTraits protocol provides read-write access to get and set trait values on an underlying container. UIKit uses this protocol to facilitate working with instances of UITraitCollection, which are immutable and read-only. The UITraitCollection initializer init(mutations:) uses an instance of UIMutableTraits, which enables you to set a batch of trait values in one method call. UITraitOverrides conforms to UIMutableTraits, making it easy to set trait overrides on trait environments such as views and view controllers.
When you define a custom trait, declare a property for the trait in an extension to UIMutableTraits so that you can access your custom trait using standard property syntax.
The following example defines an extension and sets the theme on the traitOverrides property:
// ThemeTrait conforms to UITraitDefinition, and has a defaultValue type of Theme
extension UIMutableTraits {
var theme: Theme {
get { self[ThemeTrait.self] }
set { self[ThemeTrait.self] = newValue }
}
}
// Apply an override for the custom theme trait.
view.traitOverrides.theme = .monochromeTopics
Getting and setting trait values
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