create a dispatchgroup in swift

To create a DispatchGroup in Swift, simply initialize a new instance of DispatchGroup:

main.swift
let dispatchGroup = DispatchGroup()
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Once you have a dispatch group, you can use it to manage and track multiple concurrent tasks. Whenever a task starts, you can call the enter() method of the dispatch group, and when the task completes, call the leave() method. This allows the dispatch group to keep track of how many tasks are still executing:

main.swift
DispatchQueue.global(qos: .userInitiated).async(group: dispatchGroup) {
    // Enter the dispatch group before running the task
    dispatchGroup.enter()

    // Perform some task asynchronously
    someAsynchronousTask { result in
        // When the task completes, leave the dispatch group
        dispatchGroup.leave()
    }
}
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In the above example, the dispatch group is used to manage an asynchronous task that is executed on a global queue. The enter() method is called before the task is executed, and the leave() method is called when the task completes. This ensures that the dispatch group will accurately track the number of tasks that are still running.

Once you have added all of your tasks to the dispatch group, you can use the notify() method to perform a block of code once all tasks have completed:

main.swift
dispatchGroup.notify(queue: DispatchQueue.main) {
    // All tasks have completed
    print("All tasks have completed!")
}
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In the above example, the notify() method is called on the dispatch group, passing in a block of code to be executed once all tasks have completed. This block of code will be executed on the main queue, ensuring that any UI updates are performed on the main thread.

Overall, DispatchGroup is a powerful tool for managing and tracking multiple concurrent tasks in Swift.