一个简单的Swift 2.0方法来发出HTTP GET请求

HTTP请求是异步的，因此需要一种方法从HTTP请求中获取返回值。这种方法使用通知器，分布在两个类中。

示例是使用网站http://www.example.com/handler.php?do=CheckUserJson&json=检查标识符令牌的用户名和密码，该文件名为handler.php，并且在do参数上有一个switch语句以获得RESTful方法。

在viewDidLoad中，我们设置了NotifierObserver，设置了json，并调用getHTTPRequest函数。它将返回函数checkedUsernameAndPassword和从http请求返回的参数。

override func viewDidLoad() {
    super.viewDidLoad()
    // setup the Notification observer to catch the result of check username and password
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "checkedUsernameAndPassword:", name: CHECK_USERNAME_AND_PASSWORD, object: nil)        
    let username = GlobalVariables.USER_NAME
    let password = GlobalVariables.PASSWORD
    // check username and password
    if let jsonString = Utility.checkUsernameAndPasswordJson(username, password:password){
        print("json string returned = \(jsonString)")
        let url = CHECKUSERJSON+jsonString
        // CHECKUSERJSON = http://www.example.com/handler.php?do=CheckUserJson&json=
        // jsonString = {\"username\":\"demo\",\"password\":\"demo\"}"
        // the php script handles a json request and returns a string identifier           
        Utility.getHTTPRequest(url,notifierId: CHECK_USERNAME_AND_PASSWORD)
        // the returned identifier is sent to the checkedUsernaeAndPassword function when it becomes availabel.
    }
}

在Utility.swift中有两个静态函数，首先用于编码json，然后执行HTTP调用。

    static func checkUsernameAndPasswordJson(username: String, password: String) -> String?{
    let para:NSMutableDictionary = NSMutableDictionary()
        para.setValue("demo", forKey: "username")
        para.setValue("demo", forKey: "password")
    let jsonData: NSData
    do{
        jsonData = try NSJSONSerialization.dataWithJSONObject(para, options: NSJSONWritingOptions())
        let jsonString = NSString(data: jsonData, encoding: NSUTF8StringEncoding) as! String
        return jsonString
    } catch _ {
        print ("UH OOO")
        return nil
    }
}

和Http请求

    static func getHTTPRequest (url:String , notifierId: String) -> Void{
    let urlString = url
    let config = NSURLSessionConfiguration.defaultSessionConfiguration()
    let session = NSURLSession(configuration: config, delegate: nil, delegateQueue: nil)
    let safeURL = urlString.stringByAddingPercentEncodingWithAllowedCharacters(NSCharacterSet.URLQueryAllowedCharacterSet())!
    if let url = NSURL(string: safeURL){
        let request  = NSMutableURLRequest(URL: url)
        request.HTTPMethod = "GET"
        request.timeoutInterval = 60
        let taskData = session.dataTaskWithRequest(request, completionHandler: {
            (data:NSData?, response:NSURLResponse?, error:NSError?) -> Void in
            if (data != nil) {
                let result = NSString(data: data! , encoding: NSUTF8StringEncoding)
                sendNotification (notifierId, message: String(result), num: 0)
            }else{
                  sendNotification (notifierId, message: String(UTF8String: nil), num: -1)                    }
        })
    taskData.resume()
    }else{
        print("bad urlString = \(urlString)")
    }
}

sendNotification函数完成了循环。注意，在观察者中，在选择器字符串的末尾有一个“:”。这允许通知在userInfo中携带有效负载。我给它一个String和Int。

    static func sendNotification (key: String, message:String?, num: Int?){
    NSNotificationCenter.defaultCenter().postNotificationName(
        key,
        object: nil,
        userInfo:   (["message": message!,
                      "num": "\(num!)"])
    )
}

注意，使用HTTP是老式的，更喜欢HTTPS见我如何加载一个HTTP URL与应用程序传输安全启用在iOS 9?

Swift 4及以上:使用URLSession API进行数据请求

   // create the url
   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()

Swift 4及以上，可解码和结果enum

// APIError enum which shows all possible Network errors
enum APIError: Error {
    case networkError(Error)
    case dataNotFound
    case jsonParsingError(Error)
    case invalidStatusCode(Int)
    case badURL(String)
}

// Result enum to show success or failure
enum Result<T> {
    case success(T)
    case failure(AppError)
}

// dataRequest which sends request to given URL and convert to Decodable Object
func dataRequest<T: Decodable>(with url: String, objectType: T.Type, completion: @escaping (Result<T>) -> Void) {
    
    // create the url with NSURL
    guard let dataURL = URL(string: url) else {
       completion(.failure(APIError.badURL(url))
       return
    }
    
    // create the session object
    let session = URLSession.shared
    
    // now create the URLRequest object using the url object
    let request = URLRequest(url: dataURL, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 60)
    
    // create dataTask using the session object to send data to the server
    let task = session.dataTask(with: request, completionHandler: { data, response, error in
        
        guard error == nil else {
            completion(Result.failure(APIError.networkError(error!)))
            return
        }
        
        guard let data = data else {
            completion(Result.failure(AppError.dataNotFound))
            return
        }
        
        do {
            // create decodable object from data
            let decodedObject = try JSONDecoder().decode(objectType.self, from: data)
            completion(Result.success(decodedObject))
        } catch let error {
            completion(Result.failure(APIError.jsonParsingError(error as! DecodingError)))
        }
    })
    
    task.resume()
}

例子:

//如果我们想从占位符API获取todo，那么我们定义todo结构体并调用dataRequest并传递“https://jsonplaceholder.typicode.com/todos/1”字符串url。

struct ToDo: Decodable {
    let id: Int
    let userId: Int
    let title: String
    let completed: Bool
    
}

dataRequest(with: "https://jsonplaceholder.typicode.com/todos/1", objectType: ToDo.self) { (result: Result) in
    switch result {
    case .success(let object):
        print(object)
    case .failure(let error):
        print(error)
    }
}

//输出结果:

ToDo(id: 1, userId: 1, title: "delectus aut autem", completed: false)

 var post:NSString = "api=myposts&userid=\(uid)&page_no=0&limit_no=10"

    NSLog("PostData: %@",post);

    var url1:NSURL = NSURL(string: url)!

    var postData:NSData = post.dataUsingEncoding(NSASCIIStringEncoding)!

    var postLength:NSString = String( postData.length )

    var request:NSMutableURLRequest = NSMutableURLRequest(URL: url1)
    request.HTTPMethod = "POST"
    request.HTTPBody = postData
    request.setValue(postLength, forHTTPHeaderField: "Content-Length")
    request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
    request.setValue("application/json", forHTTPHeaderField: "Accept")

    var reponseError: NSError?
    var response: NSURLResponse?

    var urlData: NSData? = NSURLConnection.sendSynchronousRequest(request, returningResponse:&response, error:&reponseError)

    if ( urlData != nil ) {
        let res = response as NSHTTPURLResponse!;

        NSLog("Response code: %ld", res.statusCode);

        if (res.statusCode >= 200 && res.statusCode < 300)
        {
            var responseData:NSString  = NSString(data:urlData!, encoding:NSUTF8StringEncoding)!

            NSLog("Response ==> %@", responseData);

            var error: NSError?

            let jsonData:NSDictionary = NSJSONSerialization.JSONObjectWithData(urlData!, options:NSJSONReadingOptions.MutableContainers , error: &error) as NSDictionary

            let success:NSInteger = jsonData.valueForKey("error") as NSInteger

            //[jsonData[@"success"] integerValue];

            NSLog("Success: %ld", success);

            if(success == 0)
            {
                NSLog("Login SUCCESS");

                self.dataArr = jsonData.valueForKey("data") as NSMutableArray
                self.table.reloadData()

            } else {

                NSLog("Login failed1");
                ZAActivityBar.showErrorWithStatus("error", forAction: "Action2")
            }

        } else {

            NSLog("Login failed2");
            ZAActivityBar.showErrorWithStatus("error", forAction: "Action2")

        }
    } else {

        NSLog("Login failed3");
        ZAActivityBar.showErrorWithStatus("error", forAction: "Action2")
}

它一定会对你有帮助

下面是在Linux上使用Swift进行HTTP请求的从头到尾的说明。

首先创建一个SwiftPM包

mkdir swift-http && cd swift-http && swift package init --type executable

然后替换。/Sources/swift-http/main.swift 代码如下:

import Foundation
import FoundationNetworking

let sema = DispatchSemaphore(value: 0)

URLSession.shared.dataTask(with: URL(string: "http://numbersapi.com/42")!) {(data, response, error) in
    print(String(data: data!, encoding: .utf8) ?? String(describing: error))
    sema.signal()
}.resume()

sema.wait()

然后运行代码

swift run

输出的例子:

[6/6] Build complete!
42 is the answer to the Ultimate Question of Life, the Universe, and Everything.

注意:使用DispatchSemaphore是为了使程序在得到响应之前不会退出。

你也可以这样做:

import Foundation
import FoundationNetworking

var done = false

URLSession.shared.dataTask(with: URL(string: "http://numbersapi.com/42")!) {(data, response, error) in
    print(String(data: data!, encoding: .utf8) ?? String(describing: error))
    done = true
}.resume()

while !done { Thread.sleep(forTimeInterval: 1) }

为了让XCUITest在异步请求完成之前停止测试完成，使用这个(可能会减少100超时):

func test_api() {
    let url = URL(string: "https://jsonplaceholder.typicode.com/posts/42")!
    let exp = expectation(description: "Waiting for data")
    let task = URLSession.shared.dataTask(with: url) {(data, response, error) in
        guard let data = data else { return }
        print(String(data: data, encoding: .utf8)!)
        exp.fulfill()
    }
    task.resume()
    XCTWaiter.wait(for: [exp], timeout: 100)
}

使用URLSession + Swift

只是补充cezar的答案，如果你想使用苹果的URLSession类进行web请求，有多种方法来完成任务

简单的GET请求与URL 简单的GET请求与URL和参数 简单的GET请求与错误处理的URL 简单的POST请求与URL，参数与错误处理

1. 简单的GET请求与URL

func simpleGetUrlRequest()
    {
        let url = URL(string: "https://httpbin.org/get")!

        let task = URLSession.shared.dataTask(with: url) {(data, response, error) in
            guard let data = data else { return }
            print("The response is : ",String(data: data, encoding: .utf8)!)
            //print(NSString(data: data, encoding: String.Encoding.utf8.rawValue) as Any)
        }
        task.resume()
    }

注意:请确保您必须在pList中为http请求添加“NSAppTransportSecurity”键

<key>NSAppTransportSecurity</key>
<dict>
<key>NSAllowsArbitraryLoads</key>
<true/>
</dict>

2. 简单的GET请求与URL和参数

func simpleGetUrlWithParamRequest()
    {
        let url = URL(string: "https://www.google.com/search?q=peace")!
        
        let task = URLSession.shared.dataTask(with: url) {(data, response, error) in
            
            if error != nil || data == nil {
                print("Client error!")
                return
            }
            guard let response = response as? HTTPURLResponse, (200...299).contains(response.statusCode) else {
                print("Server error!")
                return
            }
            print("The Response is : ",response)
        }
        task.resume()
    }

3.简单的GET请求与错误处理的URL

func simpleGetUrlRequestWithErrorHandling()
    {
        let session = URLSession.shared
        let url = URL(string: "https://httpbin.org/get")!
        
        let task = session.dataTask(with: url) { data, response, error in
            
            if error != nil || data == nil {
                print("Client error!")
                return
            }
            
            guard let response = response as? HTTPURLResponse, (200...299).contains(response.statusCode) else {
                print("Server error!")
                return
            }
            
            guard let mime = response.mimeType, mime == "application/json" else {
                print("Wrong MIME type!")
                return
            }
            
            do {
                let json = try JSONSerialization.jsonObject(with: data!, options: [])
                print("The Response is : ",json)
            } catch {
                print("JSON error: \(error.localizedDescription)")
            }
            
        }
        task.resume()
    }

4. 简单的POST请求与URL，参数与错误处理。

func simplePostRequestWithParamsAndErrorHandling(){
        let configuration = URLSessionConfiguration.default
        configuration.timeoutIntervalForRequest = 30
        configuration.timeoutIntervalForResource = 30
        let session = URLSession(configuration: configuration)
        
        let url = URL(string: "https://httpbin.org/post")!
        
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.addValue("application/json", forHTTPHeaderField: "Accept")
        
        let parameters = ["username": "foo", "password": "123456"]
        
        do {
            request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
        } catch let error {
            print(error.localizedDescription)
        }
        
        let task = session.dataTask(with: request as URLRequest, completionHandler: { data, response, error in
            
            if error != nil || data == nil {
                print("Client error!")
                return
            }
            
            guard let response = response as? HTTPURLResponse, (200...299).contains(response.statusCode) else {
                print("Oops!! there is server error!")
                return
            }
            
            guard let mime = response.mimeType, mime == "application/json" else {
                print("response is not json")
                return
            }
            
            do {
                let json = try JSONSerialization.jsonObject(with: data!, options: [])
                print("The Response is : ",json)
            } catch {
                print("JSON error: \(error.localizedDescription)")
            }
            
        })
        
        task.resume()
    }

谢谢你的建议!!