如何在Swift中执行GET和POST请求？

Question

我改编自Ray Wenderlich的iOS Apprentice教程第4部分。

这段代码可以作为GET请求发送到带有简单数据库模型的Strongloop API，但是：

1. 这行得通，但我不知道为什么行得通，因为它没有调用我可以看到的实际发送请求的方法。

2. 我认为没有任何方法可以使其进入POST请求。

我的问题是：如何执行POST请求？以完全不同的方式完成吗？

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    class ViewController: UIViewController {


    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func getFromDB() {
        let url = urlWithSearchText("")
        println("URL: '\(url)'")
        if let jsonString = performGetRequestWithURL(url) {
            println("Received JSON string '\(jsonString)'")
        }
    }


    func urlWithSearchText(searchText: String) -> NSURL {
        let escapedSearchText = searchText.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)!
        let urlString = String(format: "http://localhost:3000/api/Tests", escapedSearchText)
        let url = NSURL(string: urlString)
        return url!
    }    

    func performGetRequestWithURL(url: NSURL) -> String? {
        var error: NSError?
        if let resultString = String(contentsOfURL: url, encoding: NSUTF8StringEncoding, error: &error) {
            return resultString
        } else if let error = error {
            println("Download Error: \(error)")
        } else {
            println("Unknown Download Error")
        }
        return nil
    }

这是此工作的图片：

https://dl.dropboxusercontent.com/u/14464971/Images/Messages%20Image%281477993527%29.png

Answer 1

Swift 3及以上

得到

private func httpRequest() {

    //create the url with NSURL
    let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1")! //change the url

    //create the session object
    let session = URLSession.shared

    //now create the URLRequest object using the url object
    let request = URLRequest(url: url)

    //create dataTask using the session object to send data to the server
    let task = session.dataTask(with: request as URLRequest, completionHandler: { data, response, error in

        guard error == nil else {
            return
        }

        guard let data = data else {
            return
        }

        do {
            //create json object from data
            if let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [String: Any] {
                print(json)
            }
        } catch let error {
            print(error.localizedDescription)
        }
    })
    task.resume()
}

开机自检

@IBAction func submitAction(sender: AnyObject) {

    //declare parameter as a dictionary which contains string as key and value combination. considering inputs are valid

    let parameters = ["name": nametextField.text, "password": passwordTextField.text] as Dictionary<String, String>

    //create the url with URL
    let url = URL(string: "http://myServerName.com/api")! //change the url

    //create the session object
    let session = URLSession.shared

    //now create the URLRequest object using the url object
    var request = URLRequest(url: url)
    request.httpMethod = "POST" //set http method as POST

    do {
        request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted) // pass dictionary to nsdata object and set it as request body

    } catch let error {
        print(error.localizedDescription)
    }

    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    request.addValue("application/json", forHTTPHeaderField: "Accept")

    //create dataTask using the session object to send data to the server
    let task = session.dataTask(with: request as URLRequest, completionHandler: { data, response, error in

        guard error == nil else {
            return
        }

        guard let data = data else {
            return
        }

        do {
            //create json object from data
            if let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [String: Any] {
                print(json)
                // handle json...
            }

        } catch let error {
            print(error.localizedDescription)
        }
    })
    task.resume()
}

Answer 2

下面是两种 POST 方法。取决于您是否希望它是同步的（其他一切都会等到 post 方法完成）或异步（POST 方法在后台运行，其他方法并行运行）。

方法

// POST data to url
func postDataAsynchronous(url: String, bodyData: String, completionHandler: (responseString: String!, error: NSError!) -> ()) {
    var URL: NSURL = NSURL(string: url)!
    var request:NSMutableURLRequest = NSMutableURLRequest(URL:URL)
    request.HTTPMethod = "POST";
    request.HTTPBody = bodyData.dataUsingEncoding(NSUTF8StringEncoding);

    NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()){

        response, data, error in

        var output: String!

        if data != nil {
            output = NSString(data: data, encoding: NSUTF8StringEncoding) as! String
        }

        completionHandler(responseString: output, error: error)
    }
}

// Obtain the data
func postDataSynchronous(url: String, bodyData: String, completionHandler: (responseString: String!, error: NSError!) -> ())
{
    let URL: NSURL = NSURL(string: url)!
    var request:NSMutableURLRequest = NSMutableURLRequest(URL:URL)
    request.HTTPMethod = "POST"
    request.HTTPBody = bodyData.dataUsingEncoding(NSUTF8StringEncoding);
    request.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")

    var response: NSURLResponse?
    var error: NSError?

    // Send data
    let data = NSURLConnection.sendSynchronousRequest(request, returningResponse: &response, error: &error)

    var output: String! // Default to nil

    if data != nil{
        output =  NSString(data: data!, encoding: NSUTF8StringEncoding) as! String
    }

    completionHandler(responseString: output, error: error)

}

使用它们

然后您可以像这样调用（使用）它们：

postDataSynchronous(url, bodyData: bodyData) {
    responseString, error in

        if error != nil {
            println("Error during post: \(error)")
            return
        }
        else{
            //Success
            println(responseString)
            userType = responseString // Set usertype based on server response
        }        
    }

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func postData(url: String, params: Dictionary<String, String>, completionHandler: (data: NSData?, response: NSURLResponse?, error: NSError?) -> ()) {

    // Indicate download
    UIApplication.sharedApplication().networkActivityIndicatorVisible = true

    let url = NSURL(string: url)!
    //        print("URL: \(url)")
    let request = NSMutableURLRequest(URL: url)
    let session = NSURLSession.sharedSession()
    request.HTTPMethod = "POST"
    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    request.addValue("application/json", forHTTPHeaderField: "Accept")

    // Verify downloading data is allowed
    do {
        request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: [])
    } catch let error as NSError {
        print("Error in request post: \(error)")
        request.HTTPBody = nil
    } catch {
        print("Catch all error: \(error)")
    }

    // Post the data
    let task = session.dataTaskWithRequest(request) { data, response, error in
        completionHandler(data: data, response: response, error: error)

        // Stop download indication
        UIApplication.sharedApplication().networkActivityIndicatorVisible = false // Stop download indication

    }

    task.resume()

}