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Say you have an application that access a server? How would you handle getting new data from the server?
You might feel surprised to have received so many vote-downs. The reason is that you have not provided any information concerning what you have tried to solve the problem.
Since you have not provided any specifics either, I'll assume you want some basically structured data (e.g. JSON) to send/retrieve from server.
Following code will let you send GET/POST/PUT requests and handle it easily.
public enum RESTMethod:String {
case get = "GET"
case post = "POST"
case put = "PUT"
}
public func sendRequest(_ url: String,
method: RESTMethod,
headers: [String : String],
parameters: [String : Any],
completionHandler: #escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionTask! {
let requestURL: URL
if method == .get {
let parameterString = parameters.stringFromHttpParameters()
requestURL = URL(string:"\(url)?\(parameterString)")!
} else {
requestURL = URL(string: url)!
}
var request = URLRequest(url: requestURL)
request.allHTTPHeaderFields = headers
request.httpMethod = method.rawValue
if method == .post {
let jsonData = try? JSONSerialization.data(withJSONObject: parameters)
request.httpBody = jsonData
}
request.timeoutInterval = 60
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
completionHandler(data,response,error)
}
task.resume()
return task
}
extension Dictionary {
/// Build string representation of HTTP parameter dictionary of keys and objects
func stringFromHttpParameters() -> String {
let parameterArray = self.map { (key, value) -> String in
let percentEscapedKey = (key as! String).addingPercentEncodingForURLQueryValue()!
let percentEscapedValue = (value as? String ?? "\(value)").addingPercentEncodingForURLQueryValue()!
return "\(percentEscapedKey)=\(percentEscapedValue)"
}
return parameterArray.joined(separator: "&")
}
}
Usage:
sendRequest("http://yourserver",
method: .get, // .post or .put
headers: [],
parameters: [],
completionHandler: { (data, response, error) in
// Handle response here
})
Related
I am trying to make generic post method for API call.In my loadNew method I want to add normal dictionary inside resource object.Resource contains normal data which will pass from controller class.And dictionary is passed as body of request. but while encoding "Generic parameter 'T' could not be inferred" showing. How do I use dictionary in it?
struct Resource<T> {
let url: URL
let request: URLRequest
let dictionary : [String:Any]
let parse: (Data) -> T?
}
final class Webservice {
// MARK:- Generic
func load<T>(resource: Resource<T>, completion: #escaping (T?) -> ()) {
URLSession.shared.dataTask(with: resource.url) { data, response, error in
if let data = data {
//completion call should happen in main thread
DispatchQueue.main.async {
completion(resource.parse(data))
}
} else {
completion(nil)
}
}.resume()
}
func loadNew<T>(resource: Resource<T>, completion: #escaping (T?) -> ()) {
var request = resource.request
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
do {
//FIXIT: error is getting here
let jsonBody = try JSONEncoder().encode(resource.dictionary)
request.httpBody = jsonBody
}catch{}
let session = URLSession.shared
session.dataTask(with: request) { data, response, error in
if let data = data {
//completion call should happen in main thread
DispatchQueue.main.async {
completion(resource.parse(data))
}
} else {
completion(nil)
}
}.resume()
}
}
This method is called inside my Login controller.I have also tried assign it directly to request object but same error is showing
func APICall(){
guard let url = URL(string: Constants.HostName.local + Constants.API.User_Login) else {
return
}
var request = URLRequest(url: url)
request.httpMethod = "POST"
let resources = Resource<LoginReponse>(url: url, request: request, dictionary: dict){
data in
let loginModel = try? JSONDecoder().decode(LoginReponse.self, from: data)
return loginModel
}
// var response = LoginReponse()
Webservice().loadNew(resource: resources) {
result in
if let model = result {
print(model)
}
}
}
The error is a bit misleading, and may indicate you're using an older version of Xcode. In 11.4.1, the error is much more explicit:
error: value of protocol type 'Any' cannot conform to 'Encodable'; only struct/enum/class types can conform to protocols
The problem is that [String: Any] is not Encodable, because there's no way to encode "Any" (what should happen if you passed a UIViewController here? Or a CBPeripheral?)
Instead of a dictionary here, looking at your code I would expect you to pass an encodable object here. For example:
struct Resource<Value: Decodable, Parameters: Encodable> {
let url: URL
let request: URLRequest
let parameters : Parameters?
let parse: (Data) -> Value?
}
final class Webservice {
func loadNew<Value, Parameters>(resource: Resource<Value, Parameters>, completion: #escaping (Value?) -> ()) {
var request = resource.request
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
if let parameters = resource.parameters {
request.httpBody = try? JSONEncoder().encode(parameters)
}
// ...
}
That said, I'd probably turn this system around a bit. If you want to have a Request<T> (parameterized on the thing it returns, and not on the parameters it takes to generate it), that's fine. You can pack a bit more into the struct. For example:
let baseURL = URL(string: "https://example.com/api/")!
struct Resource<Value> {
let urlRequest: URLRequest
let parse: (Data) -> Result<Value, Error>
// Things you want as default for every request
static func makeStandardURLRequest(url: URL) -> URLRequest {
var request = URLRequest(url: url)
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpMethod = "POST"
return request
}
}
// It would be nice to have a default parser when you can, but you don't have to put that
// into Webservice. The Resource can handle it.
extension Resource where Value: Decodable {
init(urlRequest: URLRequest) {
self.init(urlRequest: urlRequest, parse: { data in
Result { try JSONDecoder().decode(Value.self, from: data) }
})
}
}
And then Resources are smart about themselves:
struct LoginParameters: Encodable {
let username: String
let password: String
}
struct LoginResult: Decodable {
let authToken: String
}
extension Resource where Value == LoginResult {
static func login(parameters: LoginParameters) -> Resource {
var urlRequest = makeStandardURLRequest(url: baseURL.appendingPathComponent("login"))
urlRequest.httpBody = try? JSONEncoder().encode(parameters)
return Resource(urlRequest: urlRequest)
}
}
Of course that may get repeated a lot, so you can hoist it out:
extension Resource where Value: Decodable {
static func makeStandardURLRequest<Parameters>(endpoint: String, parameters: Parameters) -> URLRequest
where Parameters: Encodable {
var urlRequest = makeStandardURLRequest(url: baseURL.appendingPathComponent(endpoint))
urlRequest.httpBody = try? JSONEncoder().encode(parameters)
return Resource(urlRequest: urlRequest)
}
}
And then Login looks like:
extension Resource where Value == LoginResult {
static func login(parameters: LoginParameters) -> Resource {
return makeStandardURLRequest(endpoint: "login", parameters: parameters)
}
}
The point is that you can pull duplicated code into extensions; you don't need to stick it in the Webservice, or add more generic.
With that, your load gets a bit simpler and much more flexible. It focuses just on the networking part. That means that it's easier to swap out with something else (like something for unit tests) without having to mock out a bunch of functionality.
func load<Value>(request: Resource<Value>, completion: #escaping (Result<Value, Error>) -> ()) {
let session = URLSession.shared
session.dataTask(with: request.urlRequest) { data, response, error in
DispatchQueue.main.async {
if let data = data {
//completion call should happen in main thread
completion(request.parse(data))
} else if let error = error {
completion(.failure(error))
} else {
fatalError("This really should be impossible, but you can construct an 'unexpected error' here.")
}
}
}.resume()
}
There's a lots of ways to do this; for another, see this AltConf talk.
This question already has answers here:
Swift: How do I return a value within an asynchronous urlsession function?
(3 answers)
Closed 5 years ago.
I am new on swift and trying to do something like that :
I have struct named Api Response :
struct ApiResponse {
var IsSuccess : Bool = false
var Message : String?
var ReturnedData : Data?
}
and have a func in another class named CommonHandler, that makes api call
public class CommonHandler {
public func CallApi(_ apiUrl : String , _ parameters : [String : Any] ) -> ApiResponse
{
var apiResponse = ApiResponse()
let url = URL(string: apiUrl)!
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = try! JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
let task = URLSession.shared.dataTask(with: request , completionHandler : { data, response, error in
if let error = error {
// handle the transport error
return
}
guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
// handle the server error
return
}
apiResponse.ReturnedData = data
apiResponse.IsSuccess = true
apiResponse.Message = "Succeed"
})
task.resume()
return apiResponse
}
}
I want to call this function in UIViewController like that :
var handler = CommonHandler()
let param :[String : String] = ["param":"param"]
let url = "url"
let response = handler.CallApi(url, param)
print(response.IsSuccess)
print(response.Message!)
I am aware that i can not use dataTask method like this. It's async.
But how can i do api call in a non-void func and return its response data ?
I parse ReturnedData json to struct then.
What is the best approach in this case ?
Thanks
Use an asynchronous completion handler
public func callApi(with url : String , parameters : [String : Any], completion: #escaping (ApiResponse?) -> () )
{
var apiResponse = ApiResponse()
let url = URL(string: apiUrl)!
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = try! JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
let task = URLSession.shared.dataTask(with: request , completionHandler : { data, response, error in
if let error = error {
// handle the transport error
completion(nil)
return
}
guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
// handle the server error
completion(nil)
return
}
apiResponse.ReturnedData = data
apiResponse.IsSuccess = true
apiResponse.Message = "Succeed"
completion(apiResponse)
})
task.resume()
}
and call it:
var handler = CommonHandler()
let param = ["param":"param"]
let url = "url"
handler.callApi(with: url, parameters: param) { response in
if let response = response {
print(response.IsSuccess)
print(response.Message!)
}
}
Note:
Please conform to the naming convention that variable and function names start with lowercase letter and use parameter labels for better readability.
I was trying to create a post method so I could reuse it further in my code.
I saw this example Returning data from async call in Swift function that gives partial solution to my problem but don't know how to call the function once I define it.
This is the function I am trying to call:
class func postRequest(url: URL, request: URLRequest, saveCookie: Bool, completionHandler: #escaping (_ postRequestStatus: [String:Any]) -> ()) {
let session = URLSession.shared
//So now no need of type conversion
let task = session.dataTask(with: request) {
(data, response, error) in
func displayError(_ error: String) {
print(error)
}
/* GUARD: Was there an error? */
guard (error == nil) else {
displayError("There was an error with your request: \(String(describing: error))")
return
}
guard let statusCode = (response as? HTTPURLResponse)?.statusCode, statusCode >= 200 && statusCode <= 299 else {
displayError("Your request returned a status code other than 2xx!")
return
}
/* GUARD: Was there any data returned? */
guard let data = data else {
displayError("No data was returned by the request!")
return
}
/* Since the incoming cookies will be stored in one of the header fields in the HTTP Response,parse through the header fields to find the cookie field and save the data */
if saveCookie{
let httpResponse: HTTPURLResponse = response as! HTTPURLResponse
let cookies = HTTPCookie.cookies(withResponseHeaderFields: httpResponse.allHeaderFields as! [String : String], for: (response?.url!)!)
HTTPCookieStorage.shared.setCookies(cookies as [AnyObject] as! [HTTPCookie], for: response?.url!, mainDocumentURL: nil)
}
let json: [String:Any]?
do
{
json = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:Any] ?? [:]
}
catch
{
displayError("Could not parse the data as JSON: '\(data)'")
return
}
guard let server_response = json else
{
displayError("Could not parse the data as JSON: '\(data)'")
return
}
if let userID = server_response["UserID"] as? Int64 {
print(userID)
completionHandler(server_response)
}else{
displayError("Username or password incorrect.")
}
}
return task.resume()
}
This is the caller function:
class func loginPostRequest(post_data: [String:Any], completionHandler: #escaping (_ postRequestStatus: [String:Any]) -> ()){
let url = URL(string: HTTPConstant.Login.Url)!
var request = URLRequest(url: url)
request.httpMethod = "POST"
var paramString = ""
for (key, value) in post_data
{
paramString = paramString + (key) + "=" + (value as! String) + "&"
}
request.httpBody = paramString.data(using: .utf8)
//in the line below I get the error message, extra argument "request" in call.
postRequest(url: url, request: request, saveCookie: true, completionHandler: { postRequestStatus in
completionHandler(postRequestStatus)
})
}
You cannot make loginPostRequest return NSDictionary because you are making async call with what you need is to create completion block same way you have create with postRequest method also from Swift 3 you need to use URLRequest with mutable var object instead of NSMutableURLRequest you need to also change the postRequest function's request argument type to URLRequest so latter no need to convert NSMutableURLRequest to URLRequest and use Swift type dictionary instead of NSDictionary
class func loginPostRequest(post_data: [String:Any], completionHandler: #escaping (_ postRequestStatus: [String:Any]) -> ()){
let url = URL(string: HTTPConstant.Login.Url)!
var request = URLRequest(url: url)
request.httpMethod = "POST"
var paramString = ""
for (key, value) in post_data
{
paramString = paramString + (key as! String) + "=" + (value as! String) + "&"
}
request.httpBody = paramString.data(using: .utf8)
postRequest(url: url, request: request, saveCookie: true, completionHandler: { postRequestStatus in
completionHandler(postRequestStatus)
})
}
Now simply changed the argument type of request to URLRequest from NSMutableURLRequest in method postRequest
class func postRequest(url: URL, request: URLRequest, saveCookie: Bool, completionHandler: #escaping (_ postRequestStatus: [String:Any]) -> ()) {
let session = URLSession.shared
//So now no need of type conversion
let task = session.dataTask(with: request) { (data, response, error) in
func displayError(_ error: String) {
print(error)
}
/* GUARD: Was there an error? */
guard (error == nil) else {
displayError("There was an error with your request: \(String(describing: error))")
return
}
guard let statusCode = (response as? HTTPURLResponse)?.statusCode, statusCode >= 200 && statusCode <= 299 else {
displayError("Your request returned a status code other than 2xx!")
return
}
/* GUARD: Was there any data returned? */
guard let data = data else {
displayError("No data was returned by the request!")
return
}
/* Since the incoming cookies will be stored in one of the header fields in the HTTP Response,parse through the header fields to find the cookie field and save the data */
if saveCookie{
let httpResponse: HTTPURLResponse = response as! HTTPURLResponse
let cookies = HTTPCookie.cookies(withResponseHeaderFields: httpResponse.allHeaderFields as! [String : String], for: (response?.url!)!)
HTTPCookieStorage.shared.setCookies(cookies as [AnyObject] as! [HTTPCookie], for: response?.url!, mainDocumentURL: nil)
}
let json: [String:Any]?
do
{
json = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:Any] ?? [:]
}
catch
{
displayError("Could not parse the data as JSON: '\(data)'")
return
}
guard let server_response = json else
{
displayError("Could not parse the data as JSON: '\(data)'")
return
}
if let userID = server_response["UserID"] as? Int64 {
print(userID)
completionHandler(server_response)
}else{
displayError("Username or password incorrect.")
}
}
return task.resume()
}
Now when you call this loginPostRequest you are having response in completion block of it.
Functions that receive a closure as parameter can be called like any other functions:
postRequest(url: yourUrlObject, request: yourUrlRequest, saveCookie: true/false, completionHandler: { postRequestStatus in
// ... code that will run once the request is done
})
If the closure is the last parameter you can pass it outside the parenthesis:
postRequest(url: yourUrlObject, request: yourUrlRequest, saveCookie: true/false) { postRequestStatus in
// ... code that will run once the request is done
})
You can check the Swift book to learn more about closures and functions.
By the way, your postRequest method looks weird, I haven't checked deeply into it, but for instance I believe although url is one of the parameters it isn't actually used. Some other answer pointed other problems into that function.
Header:
let header = ["Content-Type" : "application/x-www-form-urlencoded", "Authorization" : "Basic " + self.basicAuth];
Body:
var body : [String : AnyObject] = [:];
let body = ["grant_type" : "client_credentials", "scope" : "MessageSender"];
The Request and Serialization:
private func makeHTTPPostRequest(path: String, header: [String : String], body: [String: AnyObject], onCompletion: #escaping ServiceResponse) {
let request = NSMutableURLRequest(url: NSURL(string: path)! as URL)
// Set the method to POST
request.httpMethod = "POST"
do {
// Set the POST body for the request
let jsonBody = try JSONSerialization.data(withJSONObject: body, options: .prettyPrinted)
request.httpBody = jsonBody
let session = URLSession.shared
request.allHTTPHeaderFields = header;
let task = session.dataTask(with: request as URLRequest, completionHandler: {data, response, error -> Void in
if let httpResponse = response as? HTTPURLResponse {
if let jsonData = data {
let json:JSON = JSON(data: jsonData)
print(response)
print(json)
onCompletion(json,httpResponse, error as NSError?)
} else {
onCompletion(JSON.null,HTTPURLResponse.init(), error as NSError?)
}
}
})
task.resume()
} catch {
onCompletion(JSON.null,HTTPURLResponse.init(), nil)
}
}
}
When the request is done, it fires a 400 response with
{
"error_description" : "grant_type parameter is requiered field and it has to be non empty string.",
"error" : "invalid_request"
}
Obviously the body is not set correctly but I really don´t know why. I´m using this piece of code in other applications with no problem... .
The same request works like charm in Postman. The body in postman is set with type x-www-form-urlencoded.
Maybe the JSONSerialization is wrong ?
To send a POST request with Content-Type: application/x-www-form-urlencoded;, you need to create a URL query-like String and then convert it to a Data. Your code or any Swift Standard Library functions do not have the functionality. You may need to write it by yourself, or find a suitable third-party library. (Of course JSONSerialization is not suitable here, the String is not a JSON.)
With given a Dictionary<String, String>, you can do it like this:
var body: [String: String] = [:]
body = ["grant_type": "client_credentials", "scope": "MessageSender"]
(Simplified...)
request.httpBody = body.map{"\($0)=\($1)"}.joined(separator: "&").data(using: .utf8)
//`body.map{"\($0)=\($1)"}.joined(separator: "&")` -> grant_type=client_credentials&scope=MessageSender
(Strict... 4.10.22.6 URL-encoded form data)
extension CharacterSet {
static let wwwFormUrlencodedAllowed = CharacterSet(charactersIn: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._*" + "+")
}
extension String {
var wwwFormUrlencoded: String {
return self
.replacingOccurrences(of: " ", with: "+")
.addingPercentEncoding(withAllowedCharacters: .wwwFormUrlencodedAllowed)!
}
}
class HTTPBody {
static func wwwFormUrlencodedData(withDictionary dict: [String: String]) -> Data {
return body
.map{"\($0.wwwFormUrlencoded)=\($1.wwwFormUrlencoded)"}
.joined(separator: "&").data(using: .utf8)!
}
}
request.httpBody = HTTPBody.wwwFormUrlencodedData(withDictionary: body)
(Remember, not many servers interpret the received form data as strictly generated.)
One more, this is not a critical issue in this case, but you should better use Swift classes rather than NS-something:
typealias ServiceResponse = (JSON, HTTPURLResponse?, Error?)->Void
private func makeHTTPPostRequest(path: String, header: [String : String], body: [String: String], onCompletion: #escaping ServiceResponse) {
var request = URLRequest(url: URL(string: path)!)
// Set the method to POST
request.httpMethod = "POST"
// Set the POST body for the request (assuming your server likes strict form data)
request.httpBody = HTTPBody.wwwFormUrlencodedData(withDictionary: body)
let session = URLSession.shared
request.allHTTPHeaderFields = header;
let task = session.dataTask(with: request, completionHandler: {data, response, error -> Void in
if let httpResponse = response as? HTTPURLResponse {
if let jsonData = data {
let json:JSON = JSON(data: jsonData)
print(response)
print(json)
onCompletion(json, httpResponse, error)
} else {
onCompletion(JSON.null, httpResponse, error)
}
}
})
task.resume()
}
I'm trying to get an image uploaded to a RESTful web api and I'm getting a HTTP status 415 (unsupported media type). The strange thing is I did have it working the other day and i'm not to sure what i've changed to make it stop accepting the POST request.
My swift code:
func uploadImage(image: UIImage, userId: String, completion: () -> Void) {
parameters["userId"] = userId
let imageData = UIImageJPEGRepresentation(image, 70)
let urlRequest = urlRequestWithComponents(myUrl, parameters: parameters, imageData: imageData!)
Alamofire.upload(urlRequest.0, data: urlRequest.1)
.responseJSON { (response) in
print(response)
if let result = response.result.value as? Dictionary<String, String>{
print("have a result from uploading!")
print(result)
if let result = result["success"] {
if (result == "true") {
completion()
}
}
}
}
}
func urlRequestWithComponents(urlString:String, parameters:Dictionary<String, String>, imageData:NSData) -> (URLRequestConvertible, NSData) {
// create url request to send
let mutableURLRequest = NSMutableURLRequest(URL: NSURL(string: urlString)!)
mutableURLRequest.HTTPMethod = Alamofire.Method.POST.rawValue
let boundaryConstant = "myRandomBoundary12345";
let contentType = "multipart/form-data"
mutableURLRequest.setValue(contentType, forHTTPHeaderField: "Content-Type")
// create upload data to send
let uploadData = NSMutableData()
// add image
uploadData.appendData("\r\n--\(boundaryConstant)\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
uploadData.appendData("Content-Disposition: form-data; name=\"file\"; filename=\"file.png\"\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
uploadData.appendData("Content-Type: image/png\r\n\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
uploadData.appendData(imageData)
// add parameters
for (key, value) in parameters {
uploadData.appendData("\r\n--\(boundaryConstant)\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
uploadData.appendData("Content-Disposition: form-data; name=\"\(key)\"\r\n\r\n\(value)".dataUsingEncoding(NSUTF8StringEncoding)!)
}
uploadData.appendData("\r\n--\(boundaryConstant)--\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
// return URLRequestConvertible and NSData
return (Alamofire.ParameterEncoding.URL.encode(mutableURLRequest, parameters: nil).0, uploadData)
}
And here is what my Jersey Rest service accepts for that url:
#POST
#Path("/uploadImage")
#Produces(MediaType.APPLICATION_JSON)
#Consumes(MediaType.MULTIPART_FORM_DATA)
public String uploadImage(FormDataMultiPart form) throws IOException
{
//do stuff
}
Its driving me crazy trying to figure out what is going wrong, any help is muchly appreciated!