Created
November 11, 2016 19:44
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| import Foundation | |
| final class SafeSyncQueue { | |
| struct QueueIdentity { | |
| let label: String | |
| } | |
| let queue: DispatchQueue | |
| fileprivate let queueKey: DispatchSpecificKey<QueueIdentity> | |
| init(label: String) { | |
| self.queue = DispatchQueue(label: "com.khanlou.\(label).SafeSyncQueue") | |
| self.queueKey = DispatchSpecificKey<QueueIdentity>() | |
| self.queue.setSpecific(key: queueKey, value: QueueIdentity(label: queue.label)) | |
| } | |
| fileprivate var currentQueueIdentity: QueueIdentity? { | |
| return DispatchQueue.getSpecific(key: queueKey) | |
| } | |
| func sync(execute: ()->()) { | |
| if currentQueueIdentity?.label == queue.label { | |
| execute() | |
| } else { | |
| queue.sync(execute: execute) | |
| } | |
| } | |
| } |
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In general it is not safe to create a DispatchSpecificKey as an instance variable. Keys are compared by their address in memory, if you create and free multiple keys, they might end up sharing the same pointer. See my post on this issue: http://tom.lokhorst.eu/2018/02/leaky-abstractions-in-swift-with-dispatchqueue