The work you want to perform, encapsulated in a way that lets you attach a completion handle or execution dependencies.
- iOS 8.0+
- macOS 10.10+
- tvOS 9.0+
- watchOS 2.0+
- Xcode 6.0.1+
Dispatch encapsulates work to be performed on a dispatch queue or within a dispatch group. You can also use a work item as a
Dispatch event, registration, or cancellation handler.