Error: The file...doesn't exist when calling writeToFile on imageData

Question

I am trying to write data to a file with the following code in a completion block for NSURLSessionDownloadTask:

   void (^completionBlock)(NSURLResponse *response, NSURL *filePath, NSError *error) = ^void (NSURLResponse *response, NSURL *filePath, NSError *error) {
        dispatch_async(dispatch_get_main_queue(), ^{
            if (!error){
                NSData *imageData = [NSData dataWithContentsOfURL:filePath];
                if(imageData) NSLog(@"image is not null");

                if(pic == 1) self.imageView.image = [UIImage imageWithData:imageData];
                else if(pic==2) self.imageView2.image = [UIImage imageWithData:imageData];

                NSArray *paths = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
                NSURL *documentsDirectoryURL = [paths lastObject];
                NSURL *saveLocation;
                if(pic == 1) saveLocation = [documentsDirectoryURL URLByAppendingPathComponent:self.pictureName1];
                else if (pic == 2) saveLocation = [documentsDirectoryURL URLByAppendingPathComponent:self.pictureName2];
                else saveLocation = [documentsDirectoryURL URLByAppendingPathComponent:self.pictureName3];

                NSLog(@"for # %d writing to file %@", pic, saveLocation);

                NSError *error = nil;                
                [imageData writeToFile:[saveLocation absoluteString] options:NSAtomicWrite error: &error];
                if(error){
                    NSLog(@"FAILED\n\n\n %@ \n\n\n", [error description]);
                }
     }

I am able to display the downloaded images in UIImageViews and my null check on imageData likewise confirms it's not null. However, when I try to write the data to a file, My NSLog prints out the following error indicating that the write failed:

(log statements)
# 3 writing to file file:///var/mobile/Containers/Data/Application/3743A163-7EE1-4A5A-BF81-7D1344D6DA45/Documents/pic3.png
Error Domain=NSCocoaErrorDomain Code=4 "The file “pic1.jpg” doesn’t exist." 
UserInfo={NSFilePath=file:///var/mobile/Containers/Data/Application/3743A163-7EE1-
4A5A-BF81-7D1344D6DA45/Documents/pic1.jpg, NSUnderlyingError=0x16d67200 {Error
Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}} 

I haven't been able to find another question on SO indicating this error message for this file, and I'm finding the error message quite counterintuitive. Where is my error?

Answer 1

Instead of [saveLocation absoluteString], use [saveLocation path]. Basically the former gives you "file:///path/filename" while the latter gives you "/path/filename", which is the correct format.

Answer 2

You may be having an issue with an intermediate directory that doesn't exist. If any sub directories (folders) don't exist when writing a file, it will fail.

Here is a handly function to create a single directory of any name in the documents folder. If you try to write to this after running this it should be fine.

static func createDirIfNeeded(dirName: String) {
        let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].appendingPathComponent(dirName + "/")
        do {
            try FileManager.default.createDirectory(atPath: dir.path, withIntermediateDirectories: true, attributes: nil)
        } catch {
            print(error.localizedDescription)
        }
    }

Answer 3

Got Woking.. Thank you @superstart swift code below :

let documentsUrl =  NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first
let fileNameString = fileURL.absoluteString.stringByReplacingOccurrencesOfString("/", withString: "");
let destinationUrl = documentsUrl!.URLByAppendingPathComponent("check.m4a")

let request: NSURLRequest = NSURLRequest(URL: fileURL)
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue())
{ (response: NSURLResponse?, datas: NSData?, error: NSError?) in
    if error == nil
    {
       // datas?.writeToFile(destinationUrl.absoluteString, atomically: false);

        do
        {
            let result = try Bool(datas!.writeToFile(destinationUrl.path!, options: NSDataWritingOptions.DataWritingAtomic))
            print(result);
        }
        catch let errorLoc as NSError
        {
            print(errorLoc.localizedDescription)
        }
    }
    else
    {
        print(error?.localizedDescription);
    }
}