NSFileManager_写入数据（默认创建文件）

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        var documentsPath:String = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true).first!
        documentsPath = documentsPath.stringByAppendingString("/video.mov")
        print("\(documentsPath)")
        
        let nsdata:NSData = NSData(contentsOfURL:NSURL(string: "http://api.k780.com:88/?app=qr.get&data=test&level=L&size=6")!)!
        do {
            
            try nsdata.writeToFile(documentsPath, options: .AtomicWrite)

        }catch{
            
            print("写入失败")
        }
        
        if DirectoryExistAtPath(documentsPath) {
            print("file Exist")
        }else {
            print("file notExist!")
        }
    }

    func DirectoryExistAtPath(path:String)->Bool {
        return NSFileManager.defaultManager().fileExistsAtPath(path)
    }