Parse JSON response with Swift 3

In swift 3.0 for GET method:

var request = URLRequest(url: URL(string: "Your URL")!)        

    request.httpMethod = "GET"
    let task = URLSession.shared.dataTask(with: request) { data, response, error in
        guard let data = data, error == nil else {                                                 // check for fundamental networking error
            print("error=\(String(describing: error))")
            return
        }

        if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {           // check for http errors
            print("statusCode should be 200, but is \(httpStatus.statusCode)")
            print("response = \(String(describing: response))")
        }

        let responseString = String(data: data, encoding: .utf8)
        print("responseString = \(String(describing: responseString))")
    }
    task.resume()

In swift 3.0 for POST method:

var request = URLRequest(url: URL(string: "Your URL")!)

    request.httpMethod = "POST"
    let postString = "user_name=ABC"  // Your parameter
    request.httpBody = postString.data(using: .utf8)
    let task = URLSession.shared.dataTask(with: request) { data, response, error in
        guard let data = data, error == nil else {                                                 // check for fundamental networking error
            print("error=\(String(describing: error))")
            return
        }

        if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {           // check for http errors
            print("statusCode should be 200, but is \(httpStatus.statusCode)")
            print("response = \(String(describing: response))")
        }

        let responseString = String(data: data, encoding: .utf8)
        print("responseString = \(String(describing: responseString))")
    }
    task.resume()

Use this to parse your data:

let url = URL(string: "http://example.com/file.php")
URLSession.shared.dataTask(with:url!, completionHandler: {(data, response, error) in
    guard let data = data, error == nil else { return }

    do {
        let json = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as! [String:Any]
        let posts = json["posts"] as? [[String: Any]] ?? []
        print(posts)
    } catch let error as NSError {
        print(error)
    }
}).resume()

Use guard to check if you have data and that error is empty.

Swift 5.x version

let url = URL(string: "http://example.com/file.php")
URLSession.shared.dataTask(with:url!, completionHandler: {(data, response, error) in
    guard let data = data, error == nil else { return }

    do {
        let json = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:Any]
        let posts = json?["posts"] as? [[String: Any]] ?? []
        print(posts)
    } catch {
        print(error)
    }
}).resume()