Callback and closure test in playground

callback.playground

//: Playground - noun: a place where people can play

import UIKit

import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

var hello: () -> String = {
    return "Hello!"
}

hello()

var doubleValue: (Int) -> Int = { x in
    return x * x
}

let  double2 = doubleValue(2)

print("Double of 2 is \(double2)")


// concat name

var concatName: (String, String) -> String = {
    (firstName, lastName)in
    return firstName + " " + lastName
}


let fullName = concatName("John", "Doe")

print("Full name is \(fullName)")

//Callbacks
func testCallbackEmpty( callback: @escaping  () -> Void) {
    DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
        callback()
    }
}

testCallbackEmpty(callback: { () -> Void in
    
    DispatchQueue.main.async {
    print("Hey called here")
    }
    print("Hey called here")
})


enum Result {
    case OK, FAILED
}


func mainCallback(callback: @escaping (Result) -> Void) {
    DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
        callback(Result.OK)
    }

}

mainCallback(callback: { result in
    print("Hurray \(result)")
})