Ionic on iOS not sending request to external Api - angularjs

Question

I have custom api written in WebApi2 that serves some data in json. I'm trying to access that particular API from Ionic on iOS and Android using Angular's $http. On Android everything is ok and I'm receiving correct result. But on iOS strange thing happens, as $http even don't send request and throws error immidiately, returning http status code 0. This problem exists only on iOS emulator and iPhone. Moreover, this behavior is not observable when requesting any other site or fake test api.
What I already tried:
Add "Access-Control-Allow-Origin: *" header.
Add proxy to ionic.project, but this fixed the problem only when running Ionic Serve
Add in config.xml
configure angular to use cross-domain by setting this:
$httpProvider.defaults.useXDomain = true;
delete $httpProvider.defaults.headers.common['X-Requested-With'];
Any clues? Maybe this is server-side problem?

Answer 1

Does this also happen on an iOS version lower than 9.0? Because there has been some problems with $http since iOS 9.0. If it doesn't, it would check out this article.
Looking for solutions
When I started searching for this error I found this forum thread. It
said that the contributors had got this error too and that the error
is triggered when a network request is made using the $http service. I
used $http in my app too, but I didn’t make any request through it
when the app was starting. Also, in the forum thread it said that the
problem is triggered by adding custom headers to a network request. To
solve the problem, headers shouldn’t have a leading space in the
value. I had custom headers but I didn't have any spaces before the
value. So I decided, (wrongly as it turned out), that this article
couldn't help me.
Here’s what I tried next:
I read all the advice from Ionic's blog article again and tried to
apply it to my project - it didn’t help. I decided that as I was
getting the error in vendor files, I should try updating Ionic
Framework, Ionic CLI and all third party libraries (Angular,
Restangular, ngStorage, ...) - it took some time, but when I ran the
app again I got the same error. I created a new "clear" ionic app and
it worked properly - so I was sure that the problem was somewhere in
my code. I started debugging the app and digging around in my code in
"the old school way" - trying to cut out blocks of code and see if the
app would then work (because I got the error before it was possible to
use any Safari dev tools for debugging). In this way I found out which
line in my code was triggering this error. It was this line:
$http.defaults.headers.common.Authorization = 'Basic ' + $localStorage.user.authToken;
I use my own service in dependency
injection which executes a line of code (see above) when the service
is initialized. This is why the $http service was also causing the
error I was encountering. I removed this line from my code and
replaced it with authorization token headers in the configuration of
each request, like this:
$http.post(appConfig.apiUrl + 'profile', data, { headers: {'Authorization': $localStorage.user.authToken} })
After that my app started to load (Hurrah) which let me see some other
problems (Booo).