Swift - Read/write array of arrays to/from file

Question

Here are my files.

How can I write this array:

var listOfTasks = [["Hi", "Hello", "12:00"],["Hey there", "What's up?", "3:17"]]

to a .txt file (file.txt)? I know there are other questions about this, but they're in other languages (not Swift). I'd like for it to work on an actual iPhone. I'm happy to provide additional information if necessary. I'm new to Swift, so excuse my question if it seems too simple. NOTE: I am asking specifically about arrays containing arrays.

Thanks in advance!

where do you want this text file to live? on your computer? on the phone? — LuKenneth, Jun 02 '16 at 18:40
@LukePatterson On the phone. Why is this question getting downvoted? — atirit, Jun 02 '16 at 18:40
Duplicate : http://stackoverflow.com/questions/24097826/read-and-write-data-from-text-file — Steven B., Jun 02 '16 at 19:05
No. That question discusses strings. I'm specifically asking about arrays of arrays. — atirit, Jun 02 '16 at 20:39

score 8 · Answer 1 · edited May 23 '17 at 10:30

8

Already answered you in your other question:

Here's a full working Playground sample:

let fileUrl = NSURL(fileURLWithPath: "/tmp/foo.plist") // Your path here
let listOfTasks = [["Hi", "Hello", "12:00"], ["Hey there", "What's up?", "3:17"]]

// Save to file
(listOfTasks as NSArray).writeToURL(fileUrl, atomically: true)

// Read from file
let savedArray = NSArray(contentsOfURL: fileUrl) as! [[String]]

print(savedArray)

edited May 23 '17 at 10:30

Community

1
1

answered Jun 05 '16 at 00:00

redent84

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To be clear - the `NSArray.write(to:atomically:)` method write the array in plist structure, rather than a plain newline-separated text file. Which means this method is not suitable for exporting XCFileList. – yo1995 Feb 18 '21 at 23:25

Leo Dabus · Answer 2 · 2016-06-02T21:38:23.510

You should use NSKeyedArchiver/NSKeyedUnarchiver to read/write your array as a property list file instead of a text file. You can save your file to the preferences folder inside the Library folder:

let preferencesDirectory =  try! NSFileManager().URLForDirectory(.LibraryDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true).URLByAppendingPathComponent("Preferences", isDirectory: true)

let listOfTasksURL = preferencesDirectory.URLByAppendingPathComponent("listOfTasks.plist")

var listOfTasks: [[String]] {
    get {
        return NSKeyedUnarchiver.unarchiveObjectWithFile(listOfTasksURL.path!) as? [[String]] ?? []
    }
    set {
        NSKeyedArchiver.archiveRootObject(newValue, toFile: listOfTasksURL.path!)
    }
}

If you would like to test it in a playground file you will need to save it to the documents directory:

let documentsDirectory =  try! NSFileManager().URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)

let listOfTasksURL = documentsDirectory.URLByAppendingPathComponent("listOfTasks.plist")

var listOfTasks: [[String]] {
    get {
        return NSKeyedUnarchiver.unarchiveObjectWithFile(listOfTasksURL.path!) as? [[String]] ?? []
    }
    set {
        NSKeyedArchiver.archiveRootObject(newValue, toFile: listOfTasksURL.path!)
    }
}

listOfTasks =  [["Hi", "Hello", "12:00"],["Hey there", "What's up?", "3:17"]]

listOfTasks // [["Hi", "Hello", "12:00"], ["Hey there", "What's up?", "3:17"]]

This code seems to be for an array of strings; I have an array that contains arrays, which in turn contain **multiple strings per sub-array**. Or maybe I'm not implementing the code correctly. EDIT: Sorry, my bad, wasn't very clear. Or does this code work for multiple? — atirit, Jun 02 '16 at 21:36

Swift - Read/write array of arrays to/from file

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