TraitCollection
public class TraitCollection
Initializers
init(traitsFrom:)
Creates a trait collection that consists of traits merged from a specified array of trait collections.
public init(traitsFrom traits: [TraitCollection])
This method takes an array of one or more trait collections and merges them to create a new trait collection. If the array contains more than one element, the highest-indexed element that contains a given trait is used for that trait. For example, the following code snippet creates a trait collection with a compact horizontal size class, because the second element in the array overrides the first for that trait:
let collection1: TraitCollection = TraitCollection(horizontalSizeClass: .regular)
let collection2: TraitCollection = TraitCollection(horizontalSizeClass: .compact)
let collection3: TraitCollection = TraitCollection(traitsFrom: [collection1, collection2])
init(userInterfaceIdiom:)
Creates a trait collection that contains only a specified interface idiom.
public init(userInterfaceIdiom: UserInterfaceIdiom)
init(horizontalSizeClass:)
Creates a trait collection that contains only a specified horizontal size class.
public init(horizontalSizeClass: UserInterfaceSizeClass)
init(verticalSizeClass:)
Creates a trait collection that contains only a specified vertical size class.
public init(verticalSizeClass: UserInterfaceSizeClass)
init(userInterfaceStyle:)
Creates a trait collection that contains only the specified user interface style trait.
public init(userInterfaceStyle: UserInterfaceStyle)
init(accessibilityContrast:)
Creates a trait collection that contains only the specified accessibility contrast trait.
public init(accessibilityContrast: AccessibilityContrast)
init(userInterfaceLevel:)
Creates a trait collection that contains only the specified user interface level trait.
public init(userInterfaceLevel: UserInterfaceLevel)
init(legibilityWeight:)
Creates a trait collection that contains only the specified legibility weight trait.
public init(legibilityWeight: LegibilityWeight)
init(forceTouchCapability:)
Creates a trait collection that contains only a specified force touch capability trait.
public init(forceTouchCapability: ForceTouchCapability)
init(displayScale:)
Creates a trait collection that contains only a specified display scale.
public init(displayScale: Double)
init(displayGamut:)
Creates a trait collection that contains only the specified display gamut trait.
public init(displayGamut: DisplayGamut)
init(layoutDirection:)
Creates a trait collection that contains only the specified layout direction trait.
public init(layoutDirection: TraitEnvironmentLayoutDirection)
init(preferredContentSizeCategory:)
Creates a trait collection that contains only the specified content size category trait.
public init(preferredContentSizeCategory: ContentSizeCategory)
init(activeAppearance:)
Creates a trait collection that contains only the specified active appearance trait.
public init(activeAppearance: UserInterfaceActiveAppearance)
Properties
current
The complete set of traits for the current environment.
public private(set) static var current: TraitCollection
The framework updates the value of this property before calling several well-known methods of View, ViewController, and PresentationController. The trait collection contains a complete set of trait values describing the current environment, and does not include unspecified or unknown values.
Changing the traits on a nonmain thread does not affect the current traits on your applications’s main thread.
horizontalSizeClass
The horizontal size class of the trait collection.
public private(set) var horizontalSizeClass: UserInterfaceSizeClass =
.unspecified
verticalSizeClass
The vertical size class of the trait collection.
public private(set) var verticalSizeClass: UserInterfaceSizeClass =
.unspecified
displayScale
The display scale of the trait collection.
public private(set) var displayScale: Double = 0.0
A value of 1.0 indicates a non-Retina display and a value of 2.0 indicates a Retina display. The default display scale for a trait collection is 0.0 (indicating unspecified).
displayGamut
The gamut of the current display.
public private(set) var displayGamut: DisplayGamut = .unspecified
userInterfaceStyle
The style associated with the user interface.
public private(set) var userInterfaceStyle: UserInterfaceStyle = .unspecified
Use this trait to determine whether your interface should be configured with a dark or light appearance. The default value of this trait is set to the corresponding appearance setting on the user’s device.
userInterfaceIdiom
The user interface idiom of the trait collection.
public private(set) var userInterfaceIdiom: UserInterfaceIdiom = .unspecified
The default user interface idiom for a trait collection is UserInterfaceIdiom.unspecified.
userInterfaceLevel
The elevation level of the interface.
public private(set) var userInterfaceLevel: UserInterfaceLevel = .unspecified
Levels create a visual separation between different parts of your UI. Window content typically appears at the UserInterfaceLevel.base level. When you want parts of your UI to stand out from the underlying background, assign the UserInterfaceLevel.elevated level to them. For example, the system assigns the UserInterfaceLevel.elevated level to alerts and popovers.
layoutDirection
The layout direction associated with the current environment.
public private(set) var layoutDirection: TraitEnvironmentLayoutDirection =
.unspecified
Use this trait to determine whether the underlying environment uses a left-to-right or right-to-left orientation.
accessibilityContrast
The accessibility contrast associated with the current environment.
public private(set) var accessibilityContrast: AccessibilityContrast =
.unspecified
Use this trait to determine whether the user requested a high contrast between foreground and background content. The user sets the contrast level in Accessibility Settings.
legibilityWeight
The font weight to apply to text.
public private(set) var legibilityWeight: LegibilityWeight = .unspecified
The legibility weight reflects the value of the Bold Text display setting.
activeAppearance
A property that indicates whether the user interface has an active appearance.
public private(set) var activeAppearance: UserInterfaceActiveAppearance =
.unspecified
The active appearance varies according to window activation state.
forceTouchCapability
The force touch capability value of the trait collection.
public private(set) var forceTouchCapability: ForceTouchCapability =
.unspecified
Force Touch is available only on certain devices. On those devices, availability is determined by the user’s associated accessibility setting in Settings. Check this property’s value on app launch, and in your implementation of the traitCollectionDidChange(_:) method.
If this property does not contain a value, the meaning is equivalent to the value ForceTouchCapability.unknown.
preferredContentSizeCategory
The font sizing option preferred by the user.
public private(set) var preferredContentSizeCategory: ContentSizeCategory =
.unspecified
With dynamic text sizing, users can ask that apps display text using fonts that are larger or smaller than the normal font size defined by the system. For example, a user with a visual impairment might request a larger default font size to make it easier to read text. Use the value of this property to request a Font object that matches the user’s requested size.
imageConfiguration
An image configuration object compatible with this trait collection.
public var imageConfiguration: Image.Configuration
The Image.Configuration object in this property contains the same traits as the current trait collection.
Methods
containsTraits(in:)
Queries whether a trait collection contains all of another trait collection’s values.
public func containsTraits(in trait: TraitCollection?) -> Bool
Use this method to compare two standalone trait collections, or to compare the interface environment’s trait collection to a standalone trait collection.
hasDifferentColorAppearance(comparedTo:)
Queries whether changing between the specified and current trait collections would affect color values.
public func hasDifferentColorAppearance(comparedTo traitCollection: TraitCollection?)
-> Bool
Use this method to determine whether changing the traits of the current environment would also change the colors in your interface. For example, changing the userInterfaceStyle or accessibilityContrast property usually changes the colors of your interface.
performAsCurrent(_:)
Executes custom code using the traits of the current trait collection.
public func performAsCurrent(_ actions: () -> Void)
Use this method when you want to execute code using a set of traits that differ from those in the current trait environment. For example, you might use this method to draw part of a view’s content with a different set of traits. This method temporarily replaces the traits of the current environment with the ones found in the current TraitCollection. After the actions block finishes, the method restores the original traits to the environment.
You can call this method from any thread of your application.