mahmudahsan

func square(val:Int) throws -> Int {
    if val == 5 {
        throw SampleError.sample1
    }
    return val * val
}

let sqaureValue = try! square(val: 10)
print(sqaureValue)

mahmudahsan

let str = try? sampleThrowError()
if let str = str {
    print(str)
}
else {
    print("Str is nil")
}

mahmudahsan

do {
    try sampleThrowError()
}
catch SampleError.sample1 {
    print("Sample 1 Error caught")
}
catch {
    print("For all other cases")
}

mahmudahsan

func sampleThrowError() throws -> String {
    throw SampleError.sample1
    return ""
}

mahmudahsan

enum SampleError: Error {
    case sample1
    case sample2(message: String)
}

mahmudahsan

import UIKit
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

let pairOfNumbers  = [(2, 3), (5, 10), (4, 5)]
let operationQueue = OperationQueue()

//if set 1, it will be serial if commented it will be concurrent
operationQueue.maxConcurrentOperationCount = 1

mahmudahsan

let pairOfNumbers = [(2, 3), (5, 10), (4, 5)]

class MultiplcationOp : Operation{
    var inputPair: [(Int, Int)]?
    
    override func main() {
        guard let inputPair = inputPair else { return }
        for pair in inputPair{
            let result = pair.0 * pair.1
            print(result)

mahmudahsan

//Single BlockOperation 
var result:Int?
let multiplication = BlockOperation{
    result = 5 * 10
}
multiplication.start()
result
[/code]

Multiple operations using BlockOperation:

mahmudahsan

import UIKit
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

let workingQueue = DispatchQueue(label: "net.ithinkdiff.app", attributes: .concurrent)
let globalQueue  = DispatchQueue.global()
let defaultGroup = DispatchGroup()    //create a new group

func multiplication(_ num: (Int, Int)) -> Int{
    sleep(1) //to make the method slower

mahmudahsan

import UIKit
import PlaygroundSupport

//to run serial queue in playground always make the following true
PlaygroundPage.current.needsIndefiniteExecution = true

let mainQueue   = DispatchQueue.main
let globalQueue = DispatchQueue.global()
let serialQueue = DispatchQueue(label: "net.ithinkdiff.app")
let concurQueue = DispatchQueue(label: "net.ithinkdiff.app.concurr", attributes: .concurrent)