# next(isolation:) Waits for the next child task to complete, and returns the value it returned. ``` @backDeployed(before: macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0) mutating func next(isolation: isolated (any Actor)? = #isolation) async -> ChildTaskResult? ``` ## Return Value The value returned by the next child task that completes. ## Discussion The values returned by successive calls to this method appear in the order that the tasks *completed*, not in the order that those tasks were added to the task group. For example: ``` group.addTask { 1 } group.addTask { 2 } print(await group.next()) // Prints either "2" or "1". ``` If there aren’t any pending tasks in the task group, this method returns `nil`, which lets you write the following to wait for a single task to complete: ``` if let first = try await group.next() { return first } ``` It also lets you write code like the following to wait for all the child tasks to complete, collecting the values they returned: ``` while let value = try await group.next() { collected += value } return collected ``` Awaiting on an empty group immediately returns `nil` without suspending. You can also use a `for`-`await`-`in` loop to collect results of a task group: ``` for await try value in group { collected += value } ``` Don’t call this method from outside the task where you created this task group. In most cases, the Swift type system prevents this mistake. For example, because the `add(priority:operation:)` method is mutating, that method can’t be called from a concurrent execution context like a child task. --- 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)