Can't set headers on my WKWebView POST request

Question

I want to do a POST request to my WKWebView but the headers doesn't get set when I monitor the requests with Charles so the request fails. What is wrong here?

NSString *post = [NSString stringWithFormat: @"email=%@&password=%@", email, password];
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *contentLength = [NSString stringWithFormat:@"%d", postData.length];

NSURL *url = [NSURL URLWithString:@"http://materik.me/endpoint"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:postData];
[request setValue:contentLength forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];

[webview loadRequest:request];

And this is what Charles says the request is like:

POST /endpoint HTTP/1.1
Host: materik.me
Content-Type: application/x-www-form-urlencoded
Origin: null
Connection: keep-alive
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
User-Agent: Mozilla/5.0 (iPhone; CPU OS 8_0 like Mac OS X)
Content-Length: 0
Accept-Language: en-us
Accept-Encoding: gzip, deflate

So, as you can see, Content-Length is 0, Accept is not application/json and no request body were sent.

Thanks for any help.

Answer 1

As the OP stated, I have also confirmed in Charles that the body is 0 bytes after webView.load(request).

There's a workaround for this WKWebView bug, we will initiate a POST request using URLSession convert the data returned by the server to String and instead of loading the url we will use loadHTMLString which will:

Set the webpage contents and base URL.

and the content is our converted string:

var request = URLRequest(url: URL(string: "http://www.yourWebsite")!)
request.httpMethod = "POST"
let params = "do=something&andAgain=something"
request.httpBody = params.data(using: .utf8)

let task = URLSession.shared.dataTask(with: request) { (data : Data?, response : URLResponse?, error : Error?) in
        if data != nil {
            if let returnString = String(data: data!, encoding: .utf8) {
                self.webView.loadHTMLString(returnString, baseURL: URL(string: "http://www.yourWebsite.com")!)
            }
        }
}
task.resume()