Daemon-Devarshi/PasteboardWatcher.swift

## PasteboardWatcher.swift
//
//  PasteboardWatcher.swift
//  PasteboardWatcher
//
//  Created by Devarshi Kulshreshtha on 6/19/15.PasteboardWatcher
//  Copyright © 2015 Devarshi Kulshreshtha. All rights reserved.
//

import Cocoa

/// Protocol defining the methods which delegate has/ can implement
protocol PasteboardWatcherDelegate {

    /// the method which is invoked on delegate when a new url of desired kind is copied
    /// - Parameter copiedUrl: the newly copied url of desired kind
    func newlyCopiedUrlObtained(copiedUrl copiedUrl : NSURL)
}

/// Use this class to notify a delegate once a url with specified kind is copied
/// - Credit goes to: **Josh Goebel**
/// - His wonderful pastie: [PasteboardWatcher in objective-c](http://pastie.org/1129293)
class PasteboardWatcher : NSObject {

    // assigning a pasteboard object
    private let pasteboard = NSPasteboard.generalPasteboard()

    // to keep track of count of objects currently copied
    // also helps in determining if a new object is copied
    private var changeCount : Int

    // used to perform polling to identify if url with desired kind is copied
    private var timer: NSTimer?

    // the delegate which will be notified when desired link is copied
    var delegate: PasteboardWatcherDelegate?

    // the kinds of files for which if url is copied the delegate is notified
    private let fileKinds : [String]

    /// initializer which should be used to initialize object of this class
    /// - Parameter fileKinds: an array containing the desired file kinds
    init(fileKinds: [String]) {
        // assigning current pasteboard changeCount so that it can be compared later to identify changes
        changeCount = pasteboard.changeCount

        // assigning passed desired file kinds to respective instance variable
        self.fileKinds = fileKinds

        super.init()
    }
    /// starts polling to identify if url with desired kind is copied
    /// - Note: uses an NSTimer for polling
    func startPolling () {
        // setup and start of timer
        timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("checkForChangesInPasteboard"), userInfo: nil, repeats: true)
    }

    /// method invoked continuously by timer
    /// - Note: To keep this method as private I referred this answer at stackoverflow - [Swift - NSTimer does not invoke a private func as selector](http://stackoverflow.com/a/30947182/217586)
    @objc private func checkForChangesInPasteboard() {
        // check if there is any new item copied
        // also check if kind of copied item is string
        if let copiedString = pasteboard.stringForType(NSPasteboardTypeString) where pasteboard.changeCount != changeCount {

            // obtain url from copied link if its path extension is one of the desired extensions
            if let fileUrl = NSURL(string: copiedString) where self.fileKinds.contains(fileUrl.pathExtension!){

                // invoke appropriate method on delegate
                self.delegate?.newlyCopiedUrlObtained(copiedUrl: fileUrl)
            }

            // assign new change count to instance variable for later comparison
            changeCount = pasteboard.changeCount
        }
    }
}
	//
	// PasteboardWatcher.swift
	// PasteboardWatcher
	//
	// Created by Devarshi Kulshreshtha on 6/19/15.PasteboardWatcher
	// Copyright © 2015 Devarshi Kulshreshtha. All rights reserved.
	//

	import Cocoa

	/// Protocol defining the methods which delegate has/ can implement
	protocol PasteboardWatcherDelegate {

	/// the method which is invoked on delegate when a new url of desired kind is copied
	/// - Parameter copiedUrl: the newly copied url of desired kind
	func newlyCopiedUrlObtained(copiedUrl copiedUrl : NSURL)
	}

	/// Use this class to notify a delegate once a url with specified kind is copied
	/// - Credit goes to: Josh Goebel
	/// - His wonderful pastie: [PasteboardWatcher in objective-c](http://pastie.org/1129293)
	class PasteboardWatcher : NSObject {

	// assigning a pasteboard object
	private let pasteboard = NSPasteboard.generalPasteboard()

	// to keep track of count of objects currently copied
	// also helps in determining if a new object is copied
	private var changeCount : Int

	// used to perform polling to identify if url with desired kind is copied
	private var timer: NSTimer?

	// the delegate which will be notified when desired link is copied
	var delegate: PasteboardWatcherDelegate?

	// the kinds of files for which if url is copied the delegate is notified
	private let fileKinds : [String]

	/// initializer which should be used to initialize object of this class
	/// - Parameter fileKinds: an array containing the desired file kinds
	init(fileKinds: [String]) {
	// assigning current pasteboard changeCount so that it can be compared later to identify changes
	changeCount = pasteboard.changeCount

	// assigning passed desired file kinds to respective instance variable
	self.fileKinds = fileKinds

	super.init()
	}
	/// starts polling to identify if url with desired kind is copied
	/// - Note: uses an NSTimer for polling
	func startPolling () {
	// setup and start of timer
	timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("checkForChangesInPasteboard"), userInfo: nil, repeats: true)
	}

	/// method invoked continuously by timer
	/// - Note: To keep this method as private I referred this answer at stackoverflow - [Swift - NSTimer does not invoke a private func as selector](http://stackoverflow.com/a/30947182/217586)
	@objc private func checkForChangesInPasteboard() {
	// check if there is any new item copied
	// also check if kind of copied item is string
	if let copiedString = pasteboard.stringForType(NSPasteboardTypeString) where pasteboard.changeCount != changeCount {

	// obtain url from copied link if its path extension is one of the desired extensions
	if let fileUrl = NSURL(string: copiedString) where self.fileKinds.contains(fileUrl.pathExtension!){

	// invoke appropriate method on delegate
	self.delegate?.newlyCopiedUrlObtained(copiedUrl: fileUrl)
	}

	// assign new change count to instance variable for later comparison
	changeCount = pasteboard.changeCount
	}
	}
	}