Is NSMutableArray instance, optional by default in SWIFT?

Question

I have been using this following thing to do my plist and save data and display contents of plist in a Table View. I am using a NSMutableArray to fetch the contents of the array and display it in the table view . VC1 is my table view & VC2 is my EnterDetail VC So I have declared my code as follows -

class ListTableViewController: UITableViewController
{
var arr = NSMutableArray()

    var plistfinalpath = String()

    override func viewDidLoad()
    {
        super.viewDidLoad()


    }


    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()

    }
    override func viewDidAppear(animated: Bool)
    {


            let path = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, .UserDomainMask, true)[0]
            plistfinalpath = path.stringByAppendingString("/login.plist")
            print(plistfinalpath)
        arr = (NSMutableArray(contentsOfFile: plistfinalpath))!
            print("time of appearing\(arr)")

       /* if let temparray = NSMutableArray(contentsOfFile: plistfinalpath)
        {
            arr = temparray
        }*/




        self.tableView.reloadData()

    }

So as you can see that I have declared a 'arr' as a NSMutableArray type and it is not optional. And when I use in my didappear() the compiler forces me to force unwrap it. Why is that so why does it happens evenif I have declared 'arr' as non optional? And here comes the real problem whenever I run my app for the first time the plist is empty implies 'arr' is also empty. And since I have used forced unwrapping my app crashes due to fatal error. And if I uncomment my commented line in the above code, the if let part, it works fine . So any suggestions. Thanks.

Answer 1

there is no trouble with your NSMutableArray.

var arr = NSMutableArray()

create non optional instance of an array. so far, so good ... An expression

NSMutableArray(contentsOfFile: plistfinalpath)

can return nil, so it returns the optional value. Here you try to create another instance of NSMutableArray and assign the result to your var arr.

A mutable array containing the contents of the file specified aPath. Returns nil if the file can't be opened or if the contents of the file can't be parsed into a mutable array.

Probably the best way for you is something like

import Foundation
var arr = NSMutableArray(contentsOfFile: "somePath") ?? NSMutableArray()

Here your variable is guaranty to have the default value (an empty instance of NSMutableArray) if the file does not exist yet (or other failure happened)

Answer 2

To resolve your fatal error check your file exist or not :-

   //Check whether your file exist or not
 let path = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, .UserDomainMask, true)[0]
        plistfinalpath = path.stringByAppendingString("/login.plist")
    if NSFileManager.defaultManager().fileExistsAtPath(plistfinalpath)
    {
        arr = (NSMutableArray(contentsOfFile: plistfinalpath))!
    }

Answer 3

Declare it like

var arr : NSMutableArray = []

// Or

var arr : NSMutableArray!