Add CoalescingQueue, a FIFO queue of target/selector pairs, used for things like updating table row cells — things that should be coalesced and can be delayed minimally.

Frameworks/RSCore/RSCore.xcodeproj/project.pbxproj

@@ -105,6 +105,7 @@
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 		84B99C9B1FAE650100ECDEDB /* OPMLRepresentable.swift in Sources */ = {isa = PBXBuildFile; fileRef = 84B99C991FAE650100ECDEDB /* OPMLRepresentable.swift */; };
 		84BB45431D6909C700B48537 /* NSMutableDictionary-Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 84BB45421D6909C700B48537 /* NSMutableDictionary-Extensions.swift */; };
+		84C326872038C9F6006A025C /* CoalescingQueue.swift in Sources */ = {isa = PBXBuildFile; fileRef = 84C326862038C9F6006A025C /* CoalescingQueue.swift */; };
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 		84C632A4200D356E007BEEAA /* SendToBlogEditorApp.h in Headers */ = {isa = PBXBuildFile; fileRef = 84C632A2200D356E007BEEAA /* SendToBlogEditorApp.h */; settings = {ATTRIBUTES = (Public, ); }; };
@@ -225,6 +226,7 @@
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 		84B99C991FAE650100ECDEDB /* OPMLRepresentable.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; name = OPMLRepresentable.swift; path = RSCore/OPMLRepresentable.swift; sourceTree = "<group>"; };
 		84BB45421D6909C700B48537 /* NSMutableDictionary-Extensions.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "NSMutableDictionary-Extensions.swift"; sourceTree = "<group>"; };
+		84C326862038C9F6006A025C /* CoalescingQueue.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = CoalescingQueue.swift; path = RSCore/CoalescingQueue.swift; sourceTree = "<group>"; };
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@@ -369,6 +371,7 @@
 				848F6AE81FC2BC50002D422E /* ThreadSafeCache.swift */,
 				844B5B561FE9D36000C7C76A /* Keyboard.swift */,
 				84AD1EA420315A8700BC20B7 /* PasteboardWriterOwner.swift */,
+				84C326862038C9F6006A025C /* CoalescingQueue.swift */,
 				84CFF5241AC3C8A200CEA6C8 /* Foundation */,
 				84CFF5551AC3CF4A00CEA6C8 /* AppKit */,
 				84CFF5661AC3D13F00CEA6C8 /* Images */,
@@ -824,6 +827,7 @@
 				844F91D61D90D86100820C48 /* RSTransparentContainerView.m in Sources */,
 				84CFF56E1AC3D20A00CEA6C8 /* NSImage+RSCore.m in Sources */,
 				8453F7DF1BDF337800B1C8ED /* RSMacroProcessor.m in Sources */,
+				84C326872038C9F6006A025C /* CoalescingQueue.swift in Sources */,
 				842E45CC1ED623C7000A8B52 /* UniqueIdentifier.swift in Sources */,
 				84A8358A1D4EC7B80004C598 /* PlistProviderProtocol.swift in Sources */,
 				849A339E1AC90A0A0015BA09 /* NSTableView+RSCore.m in Sources */,

Frameworks/RSCore/RSCore/CoalescingQueue.swift

@@ -0,0 +1,95 @@
+//
+//  CoalescingQueue.swift
+//  RSCore
+//
+//  Created by Brent Simmons on 2/17/18.
+//  Copyright © 2018 Ranchero Software, LLC. All rights reserved.
+//
+
+import Foundation
+
+// Use when you want to coalesce calls for something like updating visible table cells.
+// Calls are uniqued. If you add a call with the same target and selector as a previous call, you’ll just get one call.
+// Targets are weakly-held. If a target goes to nil, the call is not performed.
+// The perform date is pushed off every time a call is added.
+// Calls are FIFO.
+
+struct QueueCall: Equatable {
+
+	weak var target: AnyObject?
+	let selector: Selector
+
+	init(target: AnyObject, selector: Selector) {
+
+		self.target = target
+		self.selector = selector
+	}
+
+	func perform() {
+
+		let _ = target?.perform(selector)
+	}
+
+	static func ==(lhs: QueueCall, rhs: QueueCall) -> Bool {
+
+		return lhs.target === rhs.target && lhs.selector == rhs.selector
+	}
+}
+
+@objc public final class CoalescingQueue: NSObject {
+
+	public let name: String
+	private let interval: TimeInterval
+	private var timer: Timer? = nil
+	private var calls = [QueueCall]()
+
+	public init(name: String, interval: TimeInterval = 0.05) {
+
+		self.name = name
+		self.interval = interval
+	}
+
+	public func add(_ target: AnyObject, _ selector: Selector) {
+
+		let queueCall = QueueCall(target: target, selector: selector)
+		add(queueCall)
+	}
+
+	@objc func timerDidFire(_ sender: Any?) {
+
+		let callsToMake = calls // Make a copy in case calls are added to the queue while performing calls.
+		resetCalls()
+		callsToMake.forEach { $0.perform() }
+	}
+}
+
+private extension CoalescingQueue {
+
+	func add(_ call: QueueCall) {
+
+		restartTimer()
+
+		if !calls.contains(call) {
+			calls.append(call)
+		}
+	}
+
+	func resetCalls() {
+
+		calls = [QueueCall]()
+	}
+
+	func restartTimer() {
+
+		invalidateTimer()
+		timer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(timerDidFire(_:)), userInfo: nil, repeats: false)
+	}
+
+	func invalidateTimer() {
+
+		if let timer = timer, timer.isValid {
+			timer.invalidate()
+		}
+		timer = nil
+	}
+}