Convert String to NSDate but still not accessing dateByAddingTimeInterval method

Question

   @IBAction func onDateChanged(sender: AnyObject) {
    let dateFormatter = NSDateFormatter()
    
   // dateFormatter.dateStyle = NSDateFormatterStyle.ShortStyle
    dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle
    
    let strDate = dateFormatter.stringFromDate(datePicker.date)
    
    let timeinterval = NSTimeInterval.abs(17 * 60) //time in seconds
    let newDate = strDate.dateByAddingTimeInterval(-timeinterval)
    // ERROR =- on the above line I get an error saying that type String does not have a method called dateByAddingTimeInterval, however I made the string a NSDate value in the variable newDate.

    
    print("\(strDate) is the date on the datePicker @")
}

As you can see I clearly converted the string value of the date picker into an NSDate in line 7, but it still is not letting me use the dateByAddingTimeInterval method because it still thinks it is a string.

Answer 1

It looks like you did the opposite of what you thought you were doing. dateFormatter.stringFromDate(datePicker.date) converts a NSDate to a String. If this was your intention, you should add your time interval to the date before converting it to a String. Like so.

let timeinterval = NSTimeInterval.abs(17 * 60) //time in seconds
let newDate = datePicker.date.dateByAddingTimeInterval(-timeinterval)
let strDate = dateFormatter.stringFromDate(newDate)
print("\(strDate) is the date on the datePicker @")