The easiest way to write NSData to a file - file

Question

NSData *data;
data = [self fillInSomeStrangeBytes];
My question is now how I can write this data on the easiest way to an file.
(I've already an NSURL file://localhost/Users/Coding/Library/Application%20Support/App/file.strangebytes)

Answer 1

NSData has a method called writeToURL:atomically: that does exactly what you want to do. Look in the documentation for NSData to see how to use it.

Answer 2

Notice that writing NSData into a file is an IO operation that may block the main thread. Especially if the data object is large.
Therefore it is advised to perform this on a background thread, the easiest way would be to use GCD as follows:
// Use GCD's background queue
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
// Generate the file path
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:#"yourfilename.dat"];
// Save it into file system
[data writeToFile:dataPath atomically:YES];
});

Answer 3

writeToURL:atomically: or writeToFile:atomically: if you have a filename instead of a URL.

Answer 4

You also have writeToFile:options:error: or writeToURL:options:error: which can report error codes in case the saving of the NSData failed for any reason. For example:
NSError *error;
NSURL *folder = [[NSFileManager defaultManager] URLForDirectory:NSApplicationSupportDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:true error:&error];
if (!folder) {
NSLog(#"%s: %#", __FUNCTION__, error); // handle error however you would like
return;
}
NSURL *fileURL = [folder URLByAppendingPathComponent:filename];
BOOL success = [data writeToURL:fileURL options:NSDataWritingAtomic error:&error];
if (!success) {
NSLog(#"%s: %#", __FUNCTION__, error); // handle error however you would like
return;
}

Answer 5

The easiest way, if you want to do this a few times manually instead of coding, is to only use your mouse:
Put a breakpoint one line after your NSdata are fulfilled.
Hold your mouse over your NSData variable, click on the Eye button, and then export.
After that chose the storage details (name/extension/location of the file).
Click on "Save" and you are done!