what is differant 'import Cocoa' and 'import Foundation' in Xcode's Playground

Question

This code is working good in Playground

import Foundation

let stringDate : NSString = "1403437865"
let date = NSDate(timeIntervalSince1970:stringDate.doubleValue)

var outputFormat = NSDateFormatter()
outputFormat.locale = NSLocale(localeIdentifier:"ko_KR")
outputFormat.dateStyle = .MediumStyle
outputFormat.timeStyle = .MediumStyle
println("Result: \(outputFormat.stringFromDate(date))")

but this code is not working in Playground

import Cocoa

let stringDate : NSString = "1403437865"
let date = NSDate(timeIntervalSince1970:stringDate.doubleValue)

var outputFormat = NSDateFormatter()
outputFormat.locale = NSLocale(localeIdentifier:"ko_KR")
outputFormat.dateStyle = .MediumStyle
outputFormat.timeStyle = .MediumStyle
println("Result: \(outputFormat.stringFromDate(date))")

only different 1 line "import Cocoa"!

Playground's bug?

Answer 1

Your playground is most likely created for the iOS platform - Cocoa is a framework for the OS X target, and its iOS counterpart is UIKit, and both contain user interface related APIs (for the respective platform). Try changing that to:

import UIKit

and it should work.

Foundation is a framework containing several APIs, such as NSString, NSDate, NSDateFormatter. It is already included in Cocoa and UIKit, so you don't need to reimport if already importing one of the 2.

However, the code you posted in your question uses classes from Foundation only, so there's no need to import either UIKit or Cocoa.