Swift convenience NSURL extension for composing mailto urls

NSURL+mailTo.swift

import Foundation

extension NSURL {
    /**
     Convenience class method for composing an `NSURL` for creating mail links with the `mailto` scheme.
     
     - parameter receipients: Email receipients
     - parameter cc: Email carbon copy receipients. (optional)
     - parameter bcc: Email blind carbon copy receipients (optional)
     - parameter subject: Subject title of the email (optional)
     - parameter body: Body message of the email (optional)
     
     - returns: `NSURL` composed by the provided parameters using the `mailto` scheme.
     */
    class func mailTo(receipients: [String], cc: [String]?, bcc: [String]?,  subject: String?, body: String?) -> NSURL? {
        let emailAddressesString = receipients.joinWithSeparator(",")
        let ccString = cc?.joinWithSeparator(",")
        let bccString = bcc?.joinWithSeparator(",")
        
        let components = NSURLComponents(string: "mailto:" + emailAddressesString)
        components?.queryItems == components?.queryItems ?? []
        ["cc": ccString, "bcc": bccString, "subject": subject, "body": body].forEach { (param, value) -> Void in
            if !((value ?? "").isEmpty) {
                components?.queryItems?.append(NSURLQueryItem(name: param, value: value))
            }
        }
        
        return components?.URL
    }
}