An example of populating a HTTPBody of NSMutableURLRequest for `application/x-www-form-urlencoded` request in response to http://stackoverflow.com/questions/28008874/post-with-swift-and-api/28009796#comment44430194_28009796

gistfile1.txt

extension NSMutableURLRequest {
    
    /// Populate the HTTPBody of `application/x-www-form-urlencoded` request
    ///
    /// :param: contentMap A dictionary of keys and values to be added to the request

    func setBodyContent(contentMap: [String : String]) {
        let parameters = map(contentMap) { (key, value) -> String in
            return "\(key)=\(value.stringByAddingPercentEscapesForQueryValue()!)"
        }
        HTTPBody = "&".join(parameters).dataUsingEncoding(NSUTF8StringEncoding)
    }
}

extension String {
    
    /// Percent escape value to be added to a URL query value as specified in RFC 3986
    ///
    /// This percent-escapes all characters except the alphanumeric character set and "-", ".", "_", and "~".
    ///
    /// http://www.ietf.org/rfc/rfc3986.txt
    ///
    /// :returns: Return precent escaped string.
    
    func stringByAddingPercentEscapesForQueryValue() -> String? {
        let characterSet = NSMutableCharacterSet.alphanumericCharacterSet()
        characterSet.addCharactersInString("-._~")
        return stringByAddingPercentEncodingWithAllowedCharacters(characterSet)
    }
}