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
– LuKenneth, Commented Jun 2, 2016 at 18:40
@LukePatterson On the phone. Why is this question getting downvoted? — dropbear
– dropbear, Commented Jun 2, 2016 at 18:40
No. That question discusses strings. I'm specifically asking about arrays of arrays. — dropbear
– dropbear, Commented Jun 2, 2016 at 20:39

Community · Accepted Answer · 2017-05-23 10:30:37Z

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, 2017 at 10:30

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answered Jun 5, 2016 at 0:00

redent84

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1 Comment

yo1995 Over a year ago

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.

Leo Dabus · Accepted Answer · 2016-06-02 21:38:23Z

2

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"]]

edited Jun 2, 2016 at 21:38

answered Jun 2, 2016 at 21:18

Leo Dabus

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2 Comments

dropbear Over a year ago

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?

Leo Dabus Over a year ago

@ghostpotato done this doesn't change much of the code

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