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libdispatch efficiency tips

I suspect most developers are using the libdispatch inefficiently due to the way it was presented to us at the time it was introduced and for many years after that, and due to the confusing documentation and API. I realized this after reading the 'concurrency' discussion on the swift-evolution mailing-list, in particular the messages from Pierre Habouzit (who is the libdispatch maintainer at Apple) are quite enlightening (and you can also find many tweets from him on the subject).

• https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170828/date.html
• https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170904/date.html
• https://twitter.com/pedantcoder

My take-aways are:

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Sorts

Bubble sort

Complexity	Space	Stable
O(n^2)	O(1)	Yes
Until array is sorted compares adjacent pairs and swaps them if they are in the wrong order.
+ Easy to implement

Selection sort

Complexity	Space	Stable

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Threads

Foundation offers a Thread class, internally based on pthread, that can be used to create new threads and execute closures.

// Detaches a new thread and uses the specified selector as the thread entry point.
Thread.detachNewThreadSelector(selector: Selector>, toTarget: Any, with: Any)

// Subclass
class MyThread: Thread {

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import Foundation

extension String {
  func replaceCharactersFromSet(characterSet: NSCharacterSet, replacementString: String = "") -> String {
    return self.componentsSeparatedByCharactersInSet(characterSet).joinWithSeparator(replacementString)
  }
}

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//
//  ConcurrentOperation.swift
//  Yevgeniy Prokoshev
//
//  Created by Yevgeniy Prokoshev on 14/08/2018.
//  Copyright © 2018 Yevgeniy Prokoshev. All rights reserved.
//

import Foundation

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//MARK: NSManagedObject Extension
public extension NSManagedObject {
    
    public static func findOrCreate<T: NSManagedObject>(with keyedValues: [String: Any], context: NSManagedObjectContext) -> T {
        let object: T? = self.findFirst(with: keyedValues, context: context)
        if let found = object {
            return found
        } else {
            var new: T!
            context.performAndWait {

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// The result is not guaranteed to be accurate. Typically, the function requires 200-400 characters to reliably guess the language of a string.
// Reference: [CFStringTokenizerCopyBestStringLanguage(_:_:)](https://developer.apple.com/reference/corefoundation/1542136-cfstringtokenizercopybeststringl)
//
import Foundation

extension String {
    func guessLanguage() -> String {
        let length = self.utf16.count
        let languageCode = CFStringTokenizerCopyBestStringLanguage(self as CFString, CFRange(location: 0, length: length)) as String? ?? ""

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#import <Foundation/Foundation.h>
#import "TextInputValidator.h"
@interface EmailStringValidator : NSObject <TextInputValidator>

@end

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// This is a list of nice tips and tricks I discovered

//MARK: Tip #1

let task = urlSession.dataTask(with: url) { data, _, error
    
    switch error {
    case .error(let error as NSError) where error.code == NSURLErrorNotConnectedToInternet:
        presenter.showOfflneError()
    case .error(let error):