| // | |
| // CoalesceOperation.swift | |
| // RequestCoalesce | |
| // | |
| // Created by Nicholas Cross on 4/12/2016. | |
| // Copyright © 2016 Nicholas Cross. All rights reserved. | |
| // | |
| import Foundation | |
| public class CoalesceGroup { | |
| private var coalesceGroup: DispatchGroup | |
| private var coalesceQueue: DispatchQueue | |
| init() { | |
| self.coalesceGroup = DispatchGroup() | |
| self.coalesceQueue = DispatchQueue(label: "OperationQueue") | |
| } | |
| public func performAsync(coalesce coalesceable: Coalesceable, withForceRefresh forceRefresh: Bool = false, completed: @escaping ()->()) { | |
| DispatchQueue.global(qos: .background).async { | |
| self.perform(coalesce: coalesceable, withForceRefresh: forceRefresh, completed: completed) | |
| } | |
| } | |
| public func perform(coalesce coalesceable: Coalesceable, withForceRefresh forceRefresh: Bool = false, completed: @escaping ()->()) { | |
| guard !forceRefresh else { | |
| self._perform(coalesce: coalesceable, withForceRefresh: true, completed: completed) | |
| return | |
| } | |
| self.coalesceQueue.async { | |
| self._perform(coalesce: coalesceable, completed: completed) | |
| } | |
| } | |
| private func _perform(coalesce coalesceable: Coalesceable, withForceRefresh forceRefresh: Bool = false, completed: @escaping ()->()) { | |
| if (!forceRefresh) { | |
| self.coalesceGroup.wait() | |
| } | |
| self.coalesceGroup.enter() | |
| self.coalesceGroup.notify(queue: DispatchQueue.global(qos: .background), execute: completed) | |
| if !coalesceable.isCached || forceRefresh { | |
| coalesceable.performOperation() { | |
| DispatchQueue.global(qos: .background).async { | |
| self.coalesceGroup.leave() | |
| } | |
| } | |
| } | |
| else { | |
| self.coalesceGroup.leave() | |
| } | |
| } | |
| } | |
| public protocol Coalesceable { | |
| var isCached: Bool {get} | |
| func performOperation(complete: @escaping ()->()) | |
| } |
Queue up async requests for the same resource and retrieving first from a remote source and any queued requests from a cache