Simple post request in SwiftUI - swift

I'm beginner in SwiftUI and I'm not familiar with variable management.
I'd like to send a very simple post request like this one with SwiftUI:
let full_path : String = "https://www.example.com/get_answer?my_message=current temperature"
I've tried with this piece of code but it didn't work.
if (URL(string: full_path) != nil) {
let url = URL(string: full_path)!
var request = URLRequest(url: url)
request.httpMethod = "POST"
var decodedAnswer = String("")
do {
let task = URLSession.shared.dataTask(with: url) { data, response, error in
print(response)
decodedAnswer = String(decoding: response, as: UTF8.self)
}
}
I have the following error:
Value of optional type 'URLResponse?' must be unwrapped to a value of
type 'URLResponse'
I don't know how to get the response.
How can I get the response from a simple Post request in SwiftUI?

Multiple issues here.
You are trying to decode the URLResponse object, but what you want is the data object in the decoder.
You seem to not know about optionals. I would refer you to the basic Apple tutorials about this topic. You can find it with your favorite search engine.
You are in an async context here. Everything inside the url datasession closure will be execute after your network request returns. The code in your function will be completed by that moment and your var decodedAnswer will be out of scope. So move it out of the function in to the class/struct.
You probably want something like this:
This should be defined in class scope or you won´t be able to use it:
var decodedAnswer: String = ""
This should be in a function:
let full_path: String = "https://www.example.com/get_answer?my_message=current temperature"
if let url = URL(string: full_path) {
var request = URLRequest(url: url)
request.httpMethod = "POST"
do {
let task = URLSession.shared.dataTask(with: url) { data, response, error in
//This converts the optionals in to non optionals that could be used further on
//Be aware this will just return when something goes wrong
guard let data = data, let response = response, error == nil else{
print("Something went wrong: error: \(error?.localizedDescription ?? "unkown error")")
return
}
print(response)
decodedAnswer = String(decoding: data, as: UTF8.self)
}
task.resume()
}
}

Related

Api call to .net C sharp web api project fails in swift but works fine

I am using a asp.net back end with a login end point but no matter what I DO in the swift version of this code I get a 415 when I use it in .net and sharp the api works am not sure what am doing wrong here.
And yes I have enabled transport protocol but its not decoding the jwt token correctly for me in swift
Basically the end point returns the jet token used for accessing the api in an object
let jwtAccessToken: String = ""
let urlString = "http://url.com/login" *** hidden for security
purposes but is correct ****
func CallWebApi()
{
// create the url with URL
let url = URL(string: urlString)! // change server url accordingly
let parameters: [String: Any] = [ "username":
"user1#domain.com", "password": "pass1"]
var request = URLRequest(url: url)
request.setValue("application/x-www-form-urlencoded",
forHTTPHeaderField: "Content-Type")
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpMethod = "Post"
do {
request.httpBody = try
JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
} catch let error {
print(error.localizedDescription)
return
}
let task = URLSession.shared.dataTask(with: request) {
data, response, error in
guard
let data = data,
let response = response as? HTTPURLResponse,
error == nil
else {
// check for fundamental networking error
print("error", error ?? URLError(.badServerResponse))
return
}
guard (200 ... 299) ~= response.statusCode else {
// check for http errors
print("statusCode should be 2xx, but is \(response.statusCode)")
print("response = \(response)")
return
}
// do whatever you want with the `data`, e.g.:
do {
let responseObject = data
print(responseObject)
} catch {
print(error)
// parsing error
if let responseString = String(data: data, encoding: .utf8) {
print("responseString = \(responseString)")
} else {
print("unable to parse response as string")
}
}
}
task.resume()
}
MyModel is basically a string
import Foundation
class AuthenticationResponse: ObservableObject {
#Published var jwtToken: String
init(jwtToken: String) {
self.jwtToken = jwtToken
}
}
I think 20 years of c sharp in not helping and am doing things it way and not the swift way if someone could advice be great.
Also in csharp we were told its not great in keeping alive the http client as can degrade performance is this the same for swift and if any library's you can recommend makes the code a bit neater the api has swagger docs enabled.
Edit 3
Example response expected back
{
"id": "b181104e-ba3e-4dba-b124-4bb4a3873b17",
"firstName": "user1",
"lastName": "lastname",
"username": "user1lastname#domainname.com",
"playerId": 0,
"jwtToken": "token in is here",//hidden for security
"error": {
"eventName": null,
"errorMessage": null,
"errorDate": null,
"statusCode": null,
"json": null
},
"refreshToken": null
}
I typically send this to the end point from C sharp
{
"username": "user1#domain.com",
"password": "pass1"
}
What I found I had to do was this
let decoder = JSONDecoder()
let responseObject = try
decoder.decode(AuthenticationResponse.self, from: data)
print(responseObject)
And change my class to be off this
import Foundation
struct AuthenticationResponse: Codable {
var jwtToken: String
}
After I done that I got the expected string back but my question is how does one get this to run correctly its completing before I think I need await but also where is it best to stored the jwttoken?

How to upload data using the new swift async/await methods?

The new features in Swift with async/await allow a better control about the process and a simplification in coding. But I cannot find out how this method can be applied for requests which go above a simple data reading. E.g. I need to pass a parameter in order to get a specific answer from a SQL database in the backend (accessed via php).
At first my code about the "standard" way to start with. This function reads all customer records and stores them into an account-array:
#available(iOS 15.0, *)
static func getCustomerListFromBackend() async throws -> [Account] {
let url = URL(string: "https://xxx.de/xxx/getCustomerList.php")!
let (data, _) = try await URLSession.shared.data(from: url)
var accounts: [Account] = []
accounts = try JSONDecoder().decode([Account].self, from: data)
return accounts
}
In order to make my question clear, now a piece of code in which the central statement does not work and exist. In this function I want to check whether a customer exists in the database and I need to pass the emailAddress as a parameter.
#available(iOS 15.0, *)
static func checkCustomerExistsInBackend(emailAddress: String) async throws -> String {
let url = URL(string: "https://xxx.de/xxx/checkCustomerexists.php")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
var dataString = "EmailAddress=\(emailAddress)"
let dataD = dataString.data(using: .utf8)
// Statement which does not work but for which I need an alternative
let (data, _) = try await URLSession.shared.upload(request: request, data: dataD)
let answer = try JSONDecoder().decode(BackendMessage.self, from: data)
return answer.Message
}
Unfortunately there is no statement for URLSession.shared.upload(request: request, data: dataD) Until now (before async/await), I used URLSession.shared.uploadTask(with: request, from: dataD) and then used .resume() to process it. This method however gave me too many problems in controlling the right sequence of tasks in the app. Async/await could simplify this very much as in my first example.
So, is there a way to realize this? Any advice would be appreciated.
you could try using URLComponents something like:
func checkCustomerExistsInBackend(emailAddress: String) async throws -> String {
if let url = URL(string: "https://xxx.de/xxx/checkCustomerexists.php"),
var components = URLComponents(url: url, resolvingAgainstBaseURL: false) {
components.queryItems = [URLQueryItem(name: "EmailAddress", value: emailAddress)]
var request = URLRequest(url: components.url!)
request.httpMethod = "POST"
let (data, _) = try await URLSession.shared.data(for: request)
let answer = try JSONDecoder().decode(BackendMessage.self, from: data)
return answer.Message
}
throw URLError(.badURL)
}
My question was answered by Florian Friedrich's comment and workingdog's answer as well. To the later one I had to make a little adoption which I want to reflect here in this wrap up in case it can be helpful for someone with a similar problem. I show here 2 solutions to my problem with a few remarks.
Applying Florian's answer.
This was straightforward and worked right away:
static func checkCustomerExistsInBackend(emailAddress: String) async throws -> String {
let url = URL(string: "https://xxx.de/xxx/checkCustomerexists.php")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
let dataString = "EmailAddress=\(emailAddress)"
let dataD = dataString.data(using: .utf8)
let (data, _) = try await URLSession.shared.upload(for: request, from: dataD!, delegate: nil)
let answer = try JSONDecoder().decode(BackendMessage.self, from: data)
return answer.Message
}
The proposal from workingdog:
Here I noticed that although the url appeared to be correctly set (ending with checkCustomerexists.php?EmailAddress=test#gmx.de), the parameter did not arrive in my php object. After some tests I found out that it works when I use GET instead of POST. So in my php file I changed the line $EmailAddress = $_POST[EmailAddress]; to $EmailAddress = $_GET['EmailAddress'];. (I am sure there is a good reason for this and I am just not experienced enough to recognize this.) Accordingly the code I use for workingdog's proposal is slightly adjusted:
func checkCustomerExistsInBackend3(emailAddress: String) async throws -> String {
if let url = URL(string: "https://xxx.de/xxx/checkCustomerexists.php"),
var components = URLComponents(url: url, resolvingAgainstBaseURL: false) {
components.queryItems = [URLQueryItem(name: "EmailAddress", value: emailAddress)]
var request = URLRequest(url: components.url!)
request.httpMethod = "GET"
let (data, _) = try await URLSession.shared.data(for: request)
let answer = try JSONDecoder().decode(BackendMessage.self, from: data)
return answer.Message
}
throw URLError(.badURL)
}

Passing headers to URL with Swift URLSession

I don't feel like sharing the actual link as it may have some private information so don't be surprised if it doesn't work.
I have a link that looks like this: www.somelink.com/stuff/searchmembers?member=John
And some headers that I need to pass, like Login: Admin, Password: Admin
When I use this site everything seems to be working just fine, I put the link, make it GET and put headers in key:value format and as a result I get the list of all members, but how can I do the same with URLSession? Here's what I currently have and I don't get anything at all. What am I doing wrong there?
func getAllMembers(urlString: String) {
guard let url = URL(string: urlString) else { return }
var request = URLRequest(url: url)
request.httpMethod = "GET"
request.setValue("Admin", forHTTPHeaderField: "Login")
request.setValue("Admin", forHTTPHeaderField: "Password")
request.httpBody = "member=John".data(using: .utf8)!
URLSession.shared.dataTask(with: request) { (data, response, error) in
print(response)
print(data)
}.resume()
}
Here is What You're Doing Wrong:
Your member=John is actually a URL query parameter. In general, URL requests have query parameters as a part of the URL string itself and not the httpbody.
Quick and Dirty Solution:
You should be good to go if you remove
request.httpBody = "member=John".data(using: .utf8)!
and instead pass the whole "www.somelink.com/stuff/searchmembers?member=John" into your getAllMembers(urlString:) function.
A Better Solution:
Let's say John's username is j o h n. Your function wouldn't make it past that first guard because spaces aren't valid URL string characters.
I like to use URLComponents because it saves me the trouble of having to handle spaces and such.
Here's how I'd write your function:
func getJohnMember(urlString: String) {
//URLComponents to the rescue!
var urlBuilder = URLComponents(string: urlString)
urlBuilder?.queryItems = [
URLQueryItem(name: "member", value: "j o h n")
]
guard let url = urlBuilder?.url else { return }
var request = URLRequest(url: url)
request.httpMethod = "GET"
request.setValue("Admin", forHTTPHeaderField: "Login")
request.setValue("Admin", forHTTPHeaderField: "Password")
URLSession.shared.dataTask(with: request) { (data, response, error) in
print(response)
print(String(data: data, encoding: .utf8)) //Try this too!
}.resume()
}
Just to be clear, I would pass just "www.somelink.com/stuff/searchmembers" into the first parameter.
Now if I were to print(url) after the guard let, I'd get
www.somelink.com/stuff/searchmembers?member=j%20o%20h%20n
Much easier this way, no?
That member=John is a URL-query parameter, not part of the request body. So you need to add it to the URL itself.
func getAllMembers(urlString: String) {
guard let url = URL(string: "\(urlString)?member=John") else { return }
var request = URLRequest(url: url)
request.httpMethod = "GET"
request.setValue("Admin", forHTTPHeaderField: "Login")
request.setValue("Admin", forHTTPHeaderField: "Password")
URLSession.shared.dataTask(with: request) { (data, response, error) in
print(response)
print(data)
}.resume()
}

URLRequest - "Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value" Error (Swift)

I am trying to perform an HTTP POST request in swift that will send some data to my server using PHP file, but it crashes with the error
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
The token and selectedAreaNames (the error is in the first line) are just regular strings. What could be the problem?
let url = URL(string: "https://xxxxxxx.xxx/register.php/\(token)|\ (selectedAreaNames)")! //error is here...
var request = URLRequest(url: url)
request.httpMethod = "POST"
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
if let error = error {
print("error: \(error)")
} else {
if let response = response as? HTTPURLResponse {
print("statusCode: \(response.statusCode)")
}
if let data = data, let dataString = String(data: data, encoding: .utf8) {
print("data: \(dataString)")
}
}
}
task.resume()
Assuming that’s really how your URL must look, you can do:
let url = URL(string: "https://xxxxxxx.xxx/register.php")!
.appendingPathComponent(token + "|" + selectedAreasNames)
That will percent escape those portions of the URL (including the |).
That having been said, this is an exceedingly unusual format for a POST request, which usually has the data being posted inside the body of the request, not just added as another path component of the URL. And if this was a GET request, where the parameters are added to the URL, you’d generally see this after a ? in the URL, separating the path of the request from the query. And this structure of simply TOKEN|VALUES is an unusual query structure, too.

How to Call HTTP Get and Save in Variable In Swift?

My question is simple: how do you call a HTTP GET Request in Swift?
I am trying to retrieve specific data from server (I have the URL string), the problem is that the previous answers I saw, doesn't explain thoroughly how to request an HTTP Get and save the retrieved information in a variable to be used later? Thanks in advance!
Here's what I have so far:
let myURL = NSURL(string:"https://api.thingspeak.com/channels/CHANNEL_ID/last_entry
_id.txt");
let request = NSMutableURLRequest(url:myURL! as URL);
request.httpMethod = "GET"
Not sure what do following requesting the GET.
In your post you are missing the part that does the actual getting to of the data.
Your code should look something like this to get the value out of the text file.
var lastID: String?
let myURL = NSURL(string:"https://api.thingspeak.com/channels/1417/last_entry_id.txt");
let request = NSMutableURLRequest(url:myURL! as URL);
//request.httpMethod = "GET" // This line is not need
// Excute HTTP Request
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
// Check for error
if error != nil
{
print("error=\(error)")
return
}
// Print out response string
let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
print("responseString = \(responseString!)")
lastID = "\(responseString!)" // Sets some variable or text field. Not that its unwrapped because its an optional.
}
task.resume()