NSFileManager.defaultManager（）。createFileAtPath（）返回false

Question

在一千个print()语句之后，我终于找到了问题！ 但是，我不确定如何解决它。 问题在于：

NSFileManager.defaultManager().createFileAtPath(savePath, contents: data, attributes: nil)

根据Apple开发人员指南， returns true if the operation was successful or if the item already exists, otherwise false.此行代码returns true if the operation was successful or if the item already exists, otherwise false.

这行返回false ，我不确定为什么，因为行前面的代码似乎没问题。 有人对如何解决这个bug有任何建议吗？

其余的代码在这里：

//
//  ViewController.swift
//  Downloading An Image From The Web
//
//  Created by Jae Hyun Kim on 9/6/15.
//  Copyright © 2015 Jae Hyun Kim. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var image: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()
        let url = NSURL(string: "http://7-themes.com/data_images/out/3/6776407-beautiful-scenery-pictures.jpg")
        let urlRequest = NSURLRequest(URL: url!)

        let task = NSURLSession.sharedSession().dataTaskWithRequest(urlRequest, completionHandler: { (data, response, error) -> Void in
            if error != nil {
                print(error)
            }
            else {
                if let bach = UIImage(data: data!) {
                    //self.image.image = bach
                    let documentsDirectory:String?
                    let paths:[AnyObject] = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.PicturesDirectory, NSSearchPathDomainMask.UserDomainMask, true)
                    print(paths)
                    if paths.count > 0 {
                        documentsDirectory = paths[0] as? String
                        let savePath = documentsDirectory! + "/bach.jpg"

                        print(NSFileManager.defaultManager().createFileAtPath(savePath, contents: data, attributes: nil))

                        if NSFileManager.defaultManager().fileExistsAtPath(savePath) {
                            print("file available")
                        }
                        else {
                            print("file not available")
                        }



                        self.image.image = UIImage(contentsOfFile: savePath)
                    }
                }
            }
        })
        task!.resume()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 1

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var image: UIImageView!
    override func viewDidLoad() {
        super.viewDidLoad()

        let url = NSURL(string: "http://7-themes.com/data_images/out/3/6776407-beautiful-scenery-pictures.jpg")!
        let urlRequest = NSURLRequest(URL: url)

        let task = NSURLSession.sharedSession().dataTaskWithRequest(urlRequest, completionHandler: { (data, response, error) -> Void in


            // you should always do it from the main queue otherwise you will experience a big delay when trying to display your image
            dispatch_async(dispatch_get_main_queue()) {
                // unwrap your data
                if let data = data {
                    print(data.length)
                    // get your caches directory URL
                    let cachesDirectory = try! NSFileManager().URLForDirectory(.CachesDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
                    // create your local file url by appending your url last path component
                    let fileUrl = cachesDirectory.URLByAppendingPathComponent(url.lastPathComponent!)
                    // save downloaded data to disk
                    if data.writeToURL(fileUrl, atomically: true) {
                        print(true)
                        // load your saved image from disk
                        self.image.image = UIImage(contentsOfFile: fileUrl.path!)
                    }

                }
            }

        })
        task.resume()
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

请注意，您需要编辑您的plist，如下所示：