如何将x-www-form-urlencoded从swift 3发布到REST api

let url = URL(string: "https://api.example.com/endpoint")

var request = URLRequest(url: url!)
request.httpMethod = "POST"
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")

let parameters = [
    "username": "john",
    "password": "secret"
]

var components = URLComponents()
components.queryItems = parameters.map { (key, value) in
    URLQueryItem(name: key, value: value)
}
let body = components.percentEncodedQuery?.data(using: .utf8)

request.httpBody = body

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print("Error: \(error)")
        return
    }
    
    if let data = data {
        // 处理响应数据
    }
}
task.resume()