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A playground for a small wrapper that manages multiple DispatchWorkItems
import Foundation
import PlaygroundSupport
typealias DispatcherIdentifier = String
class Dispatcher {
private var items = [DispatcherIdentifier: DispatchWorkItem]()
private let queue: DispatchQueue
deinit {
cancelAllActions()
}
init(_ queue: DispatchQueue = .main) {
self.queue = queue
}
func schedule(after timeInterval: TimeInterval,
with identifier: DispatcherIdentifier,
on queue: DispatchQueue? = nil,
action: @escaping () -> Void) {
cancelAction(with: identifier)
print("Scheduled \(identifier)")
let item = DispatchWorkItem(block: action)
items[identifier] = item
(queue ?? self.queue).asyncAfter(deadline: .now() + timeInterval, execute: item)
}
@discardableResult
func cancelAction(with identifier: DispatcherIdentifier) -> Bool {
guard let item = items[identifier] else {
return false
}
defer {
items[identifier] = nil
}
guard !item.isCancelled else {
return false
}
item.cancel()
print("Cancelled \(identifier)")
return true
}
func cancelAllActions() {
items.keys.forEach {
items[$0]?.cancel()
items[$0] = nil
}
}
}
let dispatcher = Dispatcher()
dispatcher.schedule(after: 2, with: "first") {
print("---> Hey, I'm first")
}
dispatcher.schedule(after: 3, with: "first") {
print("---> No dude, I'm first")
}
dispatcher.schedule(after: 4, with: "second") {
print("---> I'm second, but I'll be cancelled")
}
dispatcher.schedule(after: 5, with: "third") {
print("---> And I'm third")
}
DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
dispatcher.cancelAction(with: "second")
}
PlaygroundPage.current.needsIndefiniteExecution = true
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