PFUser extension to get hash from user email

gistfile1.swift

import Foundation
import CocoaLumberjack
import Parse.PFUser

extension PFUser {
    
    var hashForEmail: String? {
        if let stringValue = self.email {
            var hash = [UInt8](count: Int(CC_SHA256_DIGEST_LENGTH), repeatedValue: 0)
            var data : NSData! = stringValue.dataUsingEncoding(NSUTF8StringEncoding)
            
            // Confirm that the length of the user name is small enough
            // to be recast when calling the hash function.
            if data.length > Int.max {
                DDLogError("Account name too long to hash: \(stringValue)")
                return .None
            }
            
            CC_SHA256(data.bytes,
                CC_LONG(data.length),
                &hash)
            
            // Convert the array of bytes into a string showing its hex representation.
            var userAccountHash = NSMutableString()
            for i in 0..<Int(CC_SHA256_DIGEST_LENGTH) {
                // Add a dash every four bytes, for readability.
                if i != 0 && i%4 == 0 {
                    userAccountHash.appendString("-")
                }
                userAccountHash.appendFormat("%02x", hash[i])
            }
            
            return String(userAccountHash)
        } else {
            return .None
        }
    }
}