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Use a DispatchSemaphore for blocking rather than a DispatchQueue.

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This commit is contained in:
Mark Jerde 2017-11-06 10:16:42 -06:00
parent 99d471f46a
commit adad531327
1 changed files with 4 additions and 5 deletions
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9
Flycut-iOS/ViewController.swift
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@ -19,7 +19,7 @@ class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSour
var rememberedSyncClippings:Bool = false
let pasteboardInteractionQueue = DispatchQueue(label: "com.Flycut.pasteboardInteractionQueue")
let alertHandlingQueue = DispatchQueue(label: "com.Flycut.alertHandlingQueue")
let alertHandlingSemaphore = DispatchSemaphore(value: 0)
let defaultsChangeHandlingQueue = DispatchQueue(label: "com.Flycut.defaultsChangeHandlingQueue")
@ -239,7 +239,7 @@ class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSour
{
alertController.addAction(UIAlertAction(title: option as? String, style: .default) { action in
selection = action.title
self.alertHandlingQueue.resume()
self.alertHandlingSemaphore.signal()
})
}
@ -250,13 +250,12 @@ class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSour
// topController should now be your topmost view controller
// Transform the asynchronous UIAlertController into a synchronous alert by suspending a GCD serial queue before presenting then placing an empty sync on that queue to block until it is resumed, and resuming after selection. The GCD sync can't complete until the selection resumes the queue.
// Transform the asynchronous UIAlertController into a synchronous alert by waiting, after presenting, on a semaphore that is initialized to zero and only signaled in the selection handler.
alertHandlingQueue.suspend()
DispatchQueue.main.async {
topController.present(alertController, animated: true)
}
alertHandlingQueue.sync { } // To wait for queue to resume.
alertHandlingSemaphore.wait() // To wait for queue to resume.
}
return selection