Parse an RFC 822 date (e.g. for RSS/Atom feeds) based on some easy to spot characteristics of the format.

RFC822DateParser.swift

// Because [EEE, ]dd MMM yyyy HH:mm[:ss] z
// we can split based on , and : and count.
// There is probably a better way to do this
// without splitting the strings.

func dateFromPubdateString(str:String) -> NSDate? {
	
	func hasDay(str:String) -> Bool {
		return str.componentsSeparatedByString(",").count > 1
	}
	func hasSeconds(str: String) -> Bool {
		return str.componentsSeparatedByString(":").count > 2
	}
	
	var format    = ""
	let formatter = NSDateFormatter()
	
	format += hasDay(str) ? "EEE, " : ""
	format += "dd MMM yyyy HH:mm"
	format += hasSeconds(str) ? ":ss z" : " z"
	
	formatter.locale     = NSLocale(localeIdentifier: "en_US_POSIX")
	formatter.dateFormat = format
	
	return formatter.dateFromString(str)
}