An action that initiates a refresh operation.
When the ``EnvironmentValues/refresh`` environment value contains an
instance of this structure, certain built-in views in the corresponding
``Environment`` begin offering a refresh capability. They apply the
instance's handler to any refresh operation that the user initiates.
By default, the environment value is `nil`, but you can use the
``View/refreshable(action:)`` modifier to create and store a new
refresh action that uses the handler that you specify:
List(mailbox.conversations) { conversation in
ConversationCell(conversation)
}
.refreshable {
await mailbox.fetch()
}
On iOS and iPadOS, the ``List`` in the example above offers a
pull to refresh gesture because it detects the refresh action. When
the user drags the list down and releases, the list calls the action's
handler. Because SwiftUI declares the handler as asynchronous, it can
safely make long-running asynchronous calls, like fetching network data.
### Refreshing custom views
You can also offer refresh capability in your custom views.
Read the ``EnvironmentValues/refresh`` environment value to get the
`RefreshAction` instance for a given ``Environment``. If you find
a non-`nil` value, change your view's appearance or behavior to offer
the refresh to the user, and call the instance to conduct the
refresh. You can call the refresh instance directly because it defines
a ``RefreshAction/callAsFunction()`` method that Swift calls
when you call the instance:
struct RefreshableView: View {
@Environment(\.refresh) private var refresh
var body: some View {
Button("Refresh") {
Task {
await refresh?()
}
}
.disabled(refresh == nil)
}
}
Be sure to call the handler asynchronously by preceding it
with `await`. Because the call is asynchronous, you can use
its lifetime to indicate progress to the user. For example,
you might reveal an indeterminate ``ProgressView`` before
calling the handler, and hide it when the handler completes.
If your code isn't already in an asynchronous context, create a
<doc://com.apple.documentation/documentation/Swift/Task> for the
method to run in. If you do this, consider adding a way for the
user to cancel the task. For more information, see
[Concurrency](https://docs.swift.org/swift-book/LanguageGuide/Concurrency.html)
in *The Swift Programming Language*.
Members (1)
method · iOS 15.0+
callAsFunction
TypeScript
callAsFunction(): Promise<void>
Swift declaration
func callAsFunction() async
Initiates a refresh action.
Don't call this method directly. SwiftUI calls it when you
call the ``RefreshAction`` structure that you get from the
``Environment``:
struct RefreshableView: View {
@Environment(\.refresh) private var refresh
var body: some View {
Button("Refresh") {
Task {
await refresh?() // Implicitly calls refresh.callAsFunction()
}
}
.disabled(refresh == nil)
}
}
For information about how Swift uses the `callAsFunction()` method to
simplify call site syntax, see
[Methods with Special Names](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#ID622)
in *The Swift Programming Language*.
For information about asynchronous operations in Swift, see
[Concurrency](https://docs.swift.org/swift-book/LanguageGuide/Concurrency.html).
