Can you explain what DispatchGroup is and how it is used in programming?

DispatchGroup is a mechanism in iOS (GCD) that allows grouping multiple asynchronous tasks and tracking their completion. With DispatchGroup, you can run several tasks in parallel and execute some code only after all tasks in the group have finished.

Example usage:

let group = DispatchGroup()

group.enter()
DispatchQueue.global().async {
    // Asynchronous task 1
    print("Task 1 completed")
    group.leave()
}

group.enter()
DispatchQueue.global().async {
    // Asynchronous task 2
    print("Task 2 completed")
    group.leave()
}

group.notify(queue: DispatchQueue.main) {
    print("All tasks are completed")
}

Thus, DispatchGroup helps synchronize multiple parallel operations and perform actions after their completion.