I cannot access REST API. CORS problem on ionic 3 iOS build

Below is a screenshot of the problem. I use Safari to check the console messages of the iOS ionic app
<https://imgur.com/a/WO3M5>

Here is how I made the api call

```
        var url = this.baseurl.baseurl();
        var data = "username=" + this.username + "&password=" + this.password + "&device_uuid=ionic";
        this.http.post(url + 'parent/parent_login_with_companyname', encodeURI(data), { headers: new __WEBPACK_IMPORTED_MODULE_4__angular_common_http__["c" /* HttpHeaders */]().set('Content-type', 'application/x-www-form-urlencoded') })
            .subscribe(function (res) {
            loading_1.dismiss();
            window.localStorage.setItem('parent_info', JSON.stringify(res));
            _this.navCtrl.setRoot(__WEBPACK_IMPORTED_MODULE_2__tabs_tabs__["a" /* TabsPage */]);
        }, function (err) {

```