DependencyValues

To access a particular dependency from the collection you use the Dependency property wrapper:

@Dependency(\.date) var date
// ...
let now = date.now

To change a dependency for a well-defined scope you can use the withDependencies(_:operation:) method:

@Dependency(\.date) var date
let now = date.now

withDependencies {
  $0.date.now = Date(timeIntervalSinceReferenceDate: 1234567890)
} operation: {
  @Dependency(\.date.now) var now: Date
  now.timeIntervalSinceReferenceDate  // 1234567890
}

The dependencies will be changed for the lifetime of the operation scope, which can be synchronous or asynchronous.

To register a dependency inside DependencyValues, you first create a type to conform to the DependencyKey protocol in order to specify the liveValue to use for the dependency when run in simulators and on devices. It can even be private:

private enum MyValueKey: DependencyKey {
  static let liveValue = 42
}

And then extend DependencyValues with a computed property that uses the key to read and write to DependencyValues:

extension DependencyValues {
  var myValue: Int {
    get { self[MyValueKey.self] }
    set { self[MyValueKey.self] = newValue }
  }
}

With those steps done you can access the dependency using the Dependency property wrapper:

@Dependency(\.myValue) var myValue
myValue  // 42

Read the article Registering dependencies for more information.

Creating and accessing values

• init

• ``subscript(key:file:function:line:)

Overriding values

• func withDependencies<R>((inout DependencyValues) throws -> Void, operation: () throws -> R) rethrows -> R

  Updates the current dependencies for the duration of a synchronous operation.

• withDependencies(from:operation:file:line:)-8e74m

Escaping contexts

• func withEscapedDependencies<R>((DependencyValues.Continuation) throws -> R) rethrows -> R

  Propagates the current dependencies to an escaping context.

Dependency values

• var assert: any AssertionEffect

  A dependency for handling assertions.

• var assertionFailure: any AssertionFailureEffect

  A dependency for failing an assertion.

• var calendar: Calendar

  The current calendar that features should use when handling dates.

• var context: DependencyContext

  The current dependency context.

• var continuousClock: any Clock<Duration>

  The current clock that features should use when a ContinuousClock would be appropriate.

• var date: DateGenerator

  A dependency that returns the current date.

• var fireAndForget: FireAndForget

  A dependency for firing off an unstructured task.

• var locale: Locale
• var mainQueue: AnySchedulerOf<DispatchQueue>

  The “main” queue.

• var mainRunLoop: AnySchedulerOf<RunLoop>

  The “main” run loop.

• var openURL: OpenURLEffect

  A dependency that opens a URL.

• var precondition: any AssertionEffect

  A dependency for handling preconditions.

• var suspendingClock: any Clock<Duration>

  The current clock that features should use when a SuspendingClock would be appropriate.

• var timeZone: TimeZone

  The current time zone that features should use when handling dates.

• var urlSession: URLSession

  The URL session that features should use to make URL requests.

• var uuid: UUIDGenerator

  A dependency that generates UUIDs.

• var withRandomNumberGenerator: WithRandomNumberGenerator

  A dependency that yields a random number generator to a closure.

Default contexts

• static var live: `Self`

  A collection of “live” dependencies.

• static var preview: `Self`

  A collection of “preview” dependencies.

• static var test: `Self`

  A collection of “test” dependencies.

Deprecations

• Deprecations

  Review unsupported dependency values APIs and their replacements.

  Read More