I am working with a poorly designed API (I don't have control over it) where even if the access token is expired, it still returns a HTTP success code but includes the 401 Unauthorized in the actual response body. So simply checking the HTTP status code isn't sufficient and I need to check the actual response.
I am making many network requests in my app to this API and when I receive the response, I need to first check whether the response is an array or a dictionary. If array, then we are good. If it's a dictionary, then I need to check the "error" field in the response dictionary which will have the 401 Unauthorized.
So every time I receive the JSON response, I have the following piece of code to return out of the function if it's an error dictionary:
guard !(myJSON is NSDictionary) && (myJSON as! NSDictionary).value(forKey: "error") != nil else {
print("Error: ", MyAppError.accessTokenExpired)
return
}
I am wondering if there is a way to prevent duplicating this piece of code in every network request function I have? Can I have this somewhere and simply call it without duplicating these lines of code each time?
Wrap it in a function like this one
func isErrorResponse(_ response: Any) -> Bool {
if let dict = response as? [String: Any], let error = dict["error"] {
print("Error: \(MyAppError.accessTokenExpired)")
return true
}
return false
}
You should use the swift data types if you are using Swift language. Although if myJSON validates with Dictionary then it will definitely be validated with [String: Any].
Create function like:
func isValidResponse(_ json: Any) -> Bool {
guard let jsonDict = json as? [String: Any], let let error = dict["error"] else { return true }
print("Error: \(error.localizedDescription)")
return false
}
Use it as:
guard YourClass.isValidResponse(myJSON) else { return }
// Valid Response - Code here...
Related
My API usually returns a certain format in JSON (simplified notation):
{
status: // http status
error?: // error handle
data?: // the response data
...
}
In my Combine operators, I take the data from a URLSession dataTaskPublisher and parse the response into a Decodable object that reflects the above schema. That works great.
However, I have an endpoint that returns the HTTP status code 201 (operation successful), and has no data at all. How would I chain this with my operators without throwing an error?
This is what I have:
publisher
.map { (data, response) in
guard data.count > 0 else {
let status = (response as! HTTPURLResponse).statusCode
return Data("{\"status\": \(status), \"data\": \"\"}".utf8)
}
return data
}
.mapError { CustomError.network(description: "\($0)")}
.decode(type: MyResponse<R>.self, decoder: self.agent.decoder)
.mapError { err -> CustomError in CustomError.decoding(description: "\(err)") }
...
As you can see, I simply construct an appropriate response, where the response's "data" is an empty string. However, this is ugly and a bit hacky, and I do not see the reason, why the pipeline should continue with parsing, etc, when I already have all I need. How can I interrupt it and finish the pipeline successfully for its final subscriber?
I would suggest creating a separate Publisher for handling the specific endpoint which doesn't return any Data. You can use a tryMap to check the HTTP status code and throw an error in case it's not in the accepted range. If you don't care about the result, only that there was a successful response, you can map to a Void. If you care about the result (or the status code), you can map to that too.
extension URLSession.DataTaskPublisher {
func emptyBodyResponsePublisher() -> AnyPublisher<Void, CustomError> {
tryMap { _, response in
guard let httpResponse = response as? HTTPURLResponse else { throw CustomError.nonHTTPResponse }
let statusCode = httpResponse.statusCode
guard (200..<300).contains(statusCode) else { throw CustomError.incorrectStatusCode(statusCode) }
return Void()
}.mapError { CustomError.network($0) }
.eraseToAnyPublisher()
}
}
I am in the process of implementing a REST API with Swift. Of course, part of this API is using HTTP requests to retrieve and send data.
Full disclosure, I am inexperienced with Swift and am using this as a learning project to get my feet wet, so to speak. But it's turned into much more of a difficult project than I anticipated.
In implementing the first get method, I have (finally) gotten rid of all the compilation errors. However, when I call the function which utilizes the URLRequest, URLSession, dataTask, etc, it is never entered.
Upon debugging the program, I can watch the program execution reach the CompletionHandler, and skip over it right to "task.resume()."
A similar construction works in a Swift Playground, but does not work in the actual project proper.
So far I have tried a few things, namely making the function access a class instance variable, in hopes that that would force it to execute. But it does not.
I think the issue may be dealing with synchronicity, and perhaps I need to use a Semaphore, but I want to make sure I'm not missing anything obvious first.
import Foundation
/**
A class to wrap all GET and POST requests, to avoid the necessity of repeatedly writing request code in each API method.
*/
class BasicRequest {
private var url: URL
private var header: [String: String]
private var responseType: String
private var jsonResponse: Any?
init(url: URL, header: [String: String], responseType: String) {
self.url = url
self.header = header
self.responseType = responseType
} //END INIT
public func requestJSON() -> Any {
// Create the URLRequest object, and fill the header with the header fields as provided.
var urlRequest = URLRequest(url: self.url)
for (value, key) in self.header {
urlRequest.addValue(value, forHTTPHeaderField: key)
}
let task = URLSession.shared.dataTask(with: urlRequest) { (data, response, error) in
print("Entered the completion handler")
if error != nil {
return
}
guard let httpResponse = response as? HTTPURLResponse, 200 == httpResponse.statusCode else {
print("HTTP Request unsuccessful")
return
}
guard let mime = response?.mimeType, mime == "application/json" else {
print("Not a JSON response")
return
}
do {
let json = try JSONSerialization.jsonObject(with: data!, options: [])
print(json)
self.jsonResponse = json
} catch {
print("Could not transform to JSON")
return
}
}
task.resume()
return "Function has returned"
} //END REQUESTJSON
}
The expected result would be returning a JSON object, however that does not seem to be the case.
With respect to error messages, I get none. The only log I get in the debugger is the boilerplate "process exited with code 0."
To be truthful, I'm at a loss with what is causing this not to work.
It appears you're writing this in a command-line app. In that case the program is terminating before the URLRequest completes.
I think the issue may be dealing with synchronicity, and perhaps I need to use a Semaphore, but I want to make sure I'm not missing anything obvious first.
Exactly.
The typical tool in Swift is DispatchGroup, which is just a higher-level kind of semaphore. Call dispatchGroup.enter() before starting the request, and all dispatchGroup.leave() at the end of the completion handler. In your calling code, include dispatchGroup.wait() to wait for it. (If that's not clear, I can add code for it, but there are also a lot of SO answers you can find that will demonstrate it.)
My completion handler is never called.
This completion handler is written by stripe:
(end of step 1)
https://stripe.com/docs/mobile/ios/standard#ephemeral-key
Ive tried simplifying the function as much as possible (i made it more complex before), and putting a completion() in the end of every .case .
When i shift click on the STPJSONResponseCompletionBlock it tells me the parameters required are this:
jsonResponse
The JSON response, or nil if an error occured.
error
The error that occurred, if any.
if i call completion(nil, nil) i can crash my app, and it gives me this error:
2019-07-30 10:38:42.917984+0100 foodfactory[27595:2238502] *** Assertion failure in -[STPEphemeralKeyManager _createKey],
2019-07-30 10:38:42.929757+0100 foodfactory[27595:2238502] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Could not parse the ephemeral key response following protocol STPCustomerEphemeralKeyProvider. Make sure your backend is sending the unmodified JSON of the ephemeral key to your app. For more info, see https://stripe.com/docs/mobile/ios/standard#prepare-your-api'
But, if i pass in json as in the example below, it simply never calls..
Furthermore, i have copied the NodeJS code which sent the json to this completion handler as closely as possible (im on google cloud functions so there had to be some changes, and i checked my JSON im receiving and the ephemeral key is there, and i can access it if i write my own method to decode the json).
Also, as i can make it crash, i guess the completion handler must be being called?
This code calls the function with completion handler:
func changePaymentOptionsButtonTapped() {
// Setup customer context
let apiVersion = String(Stripe.version())
MyAPIClient.sharedClient.createCustomerKey(withAPIVersion: apiVersion) { (ephemeralKeyJson, err) in
print("ThisIsNeverCalled")
if let ephemeralKey = ephemeralKeyJson?["id"] as? String {
} else {
print("Error parsing JSON from customer creation: See: MyAPIClient - func createCustomerKey")
}
}
}
The function with completion handler:
func createCustomerKey(withAPIVersion apiVersion: String, completion: #escaping STPJSONResponseCompletionBlock) {
guard let customerId = KeychainWrapper.standard.string(forKey: Stripe_Customer_Id) else {
print("Keychain wrapper not retrieving stripe customer Id at MyAPIClient")
// completion(nil, nil)
return
}
let url = "https://us-central1-foodfactory-813ab.cloudfunctions.net/request_ephemeral_key"
Alamofire.request(url, method: .post, parameters: [
"api_version": apiVersion,
"customerId": customerId,
])
.validate(statusCode: 200..<300)
.responseJSON { responseJSON in
switch responseJSON.result {
case .success(let json):
completion(json as? [String: AnyObject], nil)
case .failure(let error):
print("Error creating customer Key (retrieving ephemeral key) with Alamofire. See: MyAPIClient - func createCustomerKey")
completion(nil, error)
}
}
}
Anyone got any suggestions? My guess is it's something to do with what im passing into the completion handler.
There's definitely an error here:
json as? [String: AnyObject]
change it to
json as? [String: Any]
The reason for it is that a JSON dictionary can contain things that aren't AnyObject - for instance, String is a struct, Int or Bool aren't objects either
This code previously works, and suddenly after several works around it stopped and return an Error 401.
Alamofire.request(WebServices.URLS().TabDataURL, method: .post, parameters: reqParams).validate().responseJSON { response in
let statusCode = (response.response?.statusCode) //Get HTTP status code
guard response.result.isSuccess, let value = response.result.value else {
// FIXME:you need to handle errors.
print("Status, Fetching News List:", statusCode)
return
}
I have check via Postman, the parameters are correct. Infact, I can also login (by passing 2 parameters). But when I want to pull in a JSON data from server, I am getting 401.
my main project doesn't have an error. but instead of returning the JSON data, it gave me an Error 401. my other projects (same code format, same server & parameters) is giving me this error.
Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.} it worked!
Also, I have check with my other projects -- it seemed I cannot connect aswell. So I suspect it could be because of Alamofire, or my Xcode?
Anyone can help me?
Hi i think your server Response is not correct because, as error indicate object should not start with array same issue i come across tell backend developer to send response in dictionary,
{NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}
let headers = [String: String]()// To add header if any
Alamofire.request(path,method: mType, parameters: parameters, encoding: JSONEncoding.default, headers : headers) .responseJSON
{ response in
//----- this code always works for me. & You don't need add header if not required.
if let JSON = response.result.value {
print("JSON: \(JSON)")
if response.response?.statusCode == 200
{
successCompletionHandler(JSON as! NSDictionary)
}
else if response.response?.statusCode == 401
{
failureCompletionHandler(JSON as! NSDictionary)
}
else
{
failureCompletionHandler(JSON as! NSDictionary)
}
}
else
{
print("error message")
failureCompletionHandler([WSAPIConst.ERROR:WSAPIConst.ERROR_MESSAGE])
}
}
I am trying to get learn how to use AlamoFire and I am having trouble.
My method so far is as follows:
func siteInfo()->String?{
var info:NSDictionary!
var str:String!
Alamofire.request(.GET, MY_API_END_POINT).responseJSON {(request, response, JSON, error) in
info = JSON as NSDictionary
str = info["access_key"] as String
//return str
}
return str
}
This returns nil which is a problem. From what I have read here, this is because the request can take a while so the closure doesn't execute till after the return. The suggested solution of moving the return into the closure does not work for me and the compiler just yells (adding ->String after (request,response,JSON,error) which gives "'String' is not a subtype of void"). Same goes for the other solution provided.
Any ideas? Even some source code that is not related to this problem, that uses AlamoFire, would be helpful.
Thanks!
One way to handle this is to pass a closure (I usually call it a completionHandler) to your siteInfo function and call that inside Alamofire.request's closure:
func siteInfo(completionHandler: (String?, NSError?) -> ()) -> () {
Alamofire.request(.GET, MY_API_END_POINT).responseJSON {
(request, response, JSON, error) in
let info = JSON as? NSDictionary // info will be nil if it's not an NSDictionary
let str = info?["access_key"] as? String // str will be nil if info is nil or the value for "access_key" is not a String
completionHandler(str, error)
}
}
Then call it like this (don't forget error handling):
siteInfo { (str, error) in
if str != nil {
// Use str value
} else {
// Handle error / nil value
}
}
In the comments you asked:
So how would you save the info you collect from the get request if you
can only do stuff inside the closure and not effect objects outside of
the closure? Also, how to keep track to know when the request has
finished?
You can save the result of the get request to an instance variable in your class from inside the closure; there's nothing about the closure stopping you from doing that. What you do from there really depends on, well, what you want to do with that data.
How about an example?
Since it looks like you're getting an access key form that get request, maybe you need that for future requests made in other functions.
In that case, you can do something like this:
Note: Asynchronous programming is a huge topic; way too much to cover here. This is just one example of how you might handle the data you get back from your asynchronous request.
public class Site {
private var _accessKey: String?
private func getAccessKey(completionHandler: (String?, NSError?) -> ()) -> () {
// If we already have an access key, call the completion handler with it immediately
if let accessKey = self._accessKey {
completionHandler(accessKey, nil)
} else { // Otherwise request one
Alamofire.request(.GET, MY_API_END_POINT).responseJSON {
(request, response, JSON, error) in
let info = JSON as? NSDictionary // info will be nil if it's not an NSDictionary
let accessKey = info?["access_key"] as? String // accessKey will be nil if info is nil or the value for "access_key" is not a String
self._accessKey = accessKey
completionHandler(accessKey, error)
}
}
}
public func somethingNeedingAccessKey() {
getAccessKey { (accessKey, error) in
if accessKey != nil {
// Use accessKey however you'd like here
println(accessKey)
} else {
// Handle error / nil accessKey here
}
}
}
}
With that setup, calling somethingNeedingAccessKey() the first time will trigger a request to get the access key. Any calls to somethingNeedingAccessKey() after that will use the value already stored in self._accessKey. If you do the rest of somethingNeedingAccessKey's work inside the closure being passed to getAccessKey, you can be sure that your accessKey will always be valid. If you need another function that needs accessKey, just write it the same way somethingNeedingAccessKey is written.
public func somethingElse() {
getAccessKey { (accessKey, error) in
if accessKey != nil {
// Do something else with accessKey
} else {
// Handle nil accessKey / error here
}
}
}