how to write into file after doing sudo vi /dir to file

Question

I entered my samplePlist.plist in the project folder and I'm trying to save the data on this .....

 var paths = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true) //Get Path of Documents Directory
        var documentsDirectory:AnyObject = paths[0]
        var path = documentsDirectory.stringByAppendingPathComponent("samplePlist.plist")
        var fileManager = NSFileManager.defaultManager()
        var fileExists:Bool = fileManager.fileExistsAtPath(path)
        var data : NSMutableDictionary?
        //Check if plist file exists at path specified
        if fileExists == false {
            //File does not exists
            data = NSMutableDictionary () //Create data dictionary for storing in plist      
        } else  {
            //File exists – retrieve data from plist inside data dictionary
            data = NSMutableDictionary(contentsOfFile: path)
        }
        data?.setValue("\(countButton)", forKey: "NumeroButton")
        data?.writeToFile(path, atomically: true) //Write data to file permanently

and i Read to the plist

//Get path of Documents directory
    var paths = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)
    var documentsDirectory:AnyObject = paths[0]
     var path = documentsDirectory.stringByAppendingPathComponent("samplePlist.plist")
//Retrieve contents from file at specified path
    var data = NSMutableDictionary(contentsOfFile: path!)
   println(path)

my problem is that ,if I try to start it on my iphone ,I do not upload the file to the My Documents folder on startup of the Application

/var/mobile/Containers/Data/Application/9CCDBD0B-FA29-4C9E-910E-9AD5F5B11E5A/Documents/samplePlist.plist fatal error: unexpectedly found nil while unwrapping an Optional value

Solution 1

Vi is what is known as a modal editor - that means it has a number of modes in which it operates.

When you first start vi it is in command mode. Some common command mode key sequences:

• :q - Quit
• :q! - Force quit
• :w - Write file
• :wq! - Forced write file and exit
• :w /path/to/my/new/file - Write to a new file
• :r /path/to/file - read file and insert into buffer

To switch into one of the editing modes:

• i - Enter insert mode infront of the current character
• r - Replace single character
• R - Enter replace mode
• a - Enter insert mode after the current character
• A - Enter insert mode at the end of the current line
• o - Open a new line below cursor and enter insert mode
• O - Open a new line above cursor and enter insert mode

To return to command mode just press Esc

There are a huge number of other keypresses in command mode - this list is pretty useful.

Solution 2

type a to append or i to insert
Refer this document for more commands

Comments

[Pricey]

Matt Jenkin's list is a good primer but if things work out too difficult, use 'nano' instead. Its probably a lot closer to the text editors your used to. Instead of writing 'vi file', write 'nano file'.