I want to convert \"2014-07-15 06:55:14.198000+00:00\" this string date to NSDate in Swift.
The first thing Apple mentions is that you cache your formatter...
Link to Apple doco stating exactly how to do this:
Cache Formatters for Efficiency Creating a date formatter is not a cheap operation. ...cache a single instance...
Use a global...
let df : DateFormatter = {
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
return formatter
}()
Then simply use that formatter anywhere...
let s = df.string(from: someDate)
or
let d = df.date(from: someString)
Or use any of the other many, many convenient methods on DateFormatter.
(If you write an extension on String, your code is completely "upside down" - you can't use any dateFormatter calls!)
Note that usually you will have a few of those globals .. such as "formatForClient" "formatForPubNub" "formatForDisplayOnInvoiceScreen" .. etc.