public class GitHubAPI: Bluebonnet {

    // baseURL for all api
    static let baseURL: NSURL = NSURL(string: "https://api.github.com")!

    /**
    for respective API
    */
    struct GetUserProfile: BluebonnetRequest {
        typealias Response = User
        typealias ErrorResponse = GitHubError
        let userName: String
        let method: HTTPMethod = .GET
        var parameters: [String: AnyObject] = [:]
        var path: String {
            return "users/\(userName.URLEscapedString)"
        }

        init(userName: String) {
            self.userName = userName
        }

        /// it is requred property for converting to request
        var URLRequest: NSURLRequest {
            return Bluebonnet.build(baseURL, path: path, method: method, parameters: parameters)
        }
    }
}

let task = GitHubAPI.requestTask(GitHubAPI.GetUserProfile(userName: userName))
task
    .progress { (oldProgress, newProgress) in
        print(newProgress.bytesWritten)
        print(newProgress.totalBytesWritten)
        return
    }
    .success { user in // type inference
        print(user.name)
        return
    }
    .failure { (errorResult, isCancelled) -> Void in
        print(errorResult?.error.description)
        print(errorResult?.response?.message
        return
    }