Because “this” cannot be read inside function(). You should try using arrow function. Which is remove the “function” and add “=>” after (succ). Such as;
cordova.plugins.SignInWithApple.signin(
{ requestedScopes: [0, 1] },
(succ) => {
console.log('succ');
console.log(succ);
this.DService.AuthUser(succ).then((res :any) => { /* this is not working under this function */
console.log('Result');
console.log(res);
});
});
Hope it helps.