Capacitor on iOS: POST request fails

Issue

I'm using Ionic (v5) + React + Capacitor to create an app for iOS and I recently got stuck with a really strange error: fetch() and axios successfully perform GET requests to the backend while POST requests are always failing.

fetch() returns "cancelled" which tells me nothing but a failure meanwhile axios generates a more descriptive error:

{
  "message": "Network Error",
  "name": "Error",
  "stack": "capacitor://localhost/static/js/8.98344607.chunk.js:2:168604\ncapacitor://localhost/static/js/8.98344607.chunk.js:2:167548",
  "config": {
    "url": "auth",
    "method": "post",
    "data": "{\"email\":\"email-here\",\"password\":\"111111\"}",
    "headers": {
      "Accept": "application/json",
      "Content-Type": "application/json"
    },
    "baseURL": "https://website.com/api/1.3/",
    "transformRequest": [
      null
    ],
    "transformResponse": [
      null
    ],
    "timeout": 0,
    "xsrfCookieName": "XSRF-TOKEN",
    "xsrfHeaderName": "X-XSRF-TOKEN",
    "maxContentLength": -1
  }
}

Already checked Apache's CORS settings, it should be OK. Could anyone suggest a fix for this?

Upd.1: part of my code that performs all api requests

const axConf: AxiosRequestConfig = {
    url: query, // string
    method: m, // string
    baseURL: global.base_uri + 'api/' + global.api_version + '/',
    headers: {
        Accept: 'application/json',
        'Content-Type': 'application/json'
    },
    data: r, // object
    validateStatus: function (status) { return status >= 200 && status < 300; }
};
return new Promise(resolve => {
    axios(axConf)
        .then(response => resolve(successRes(r, i, response.data)))
        .catch(function (error) {
                console.log(error);
                if (error.response) {
                    resolve(errorRes(i, error.response));
                } else if (error.request) {
                    resolve(errorRes(i, error.request));
                } else {
                    resolve(errorRes(i, error.message));
                }
            }
        );
});

Solution

Finally, after couple of days trying to solve this problem I found the solution. Here it is, for everyone struggling with this:

This error happens when you try to perform a HTTP request and then something in your code breaks this request. In my case that was the form: my fetch() request has been triggered by button's onClick action with type="submit" set on it and submitting the form itself triggered nothing but a state update which has been cancelling my request.

I was switching my app from Ionic v4 & Angular to Ionic v5 & React and previously the form didn't cause such behavior that's why I didn't even think this might be a thing.

I just removed onClick action from my button and set onSubmit={handleLogin} to the form itself. Then modified the code like this:

const handleLogin = (e: FormEvent) => {
    fnGetUserToken(loginData).then(...);
    e.preventDefault();
};

Note the e.preventDefault(); at the end.

In case you can not alter your code like this, I guess you could try to remove the property type="submit" from your button.

Another answer that led me to this solution.

Answered By - MullinsMikey