Store User Credit Information - ios

Question

I have followed up the BrainTree tutorial for objective-c and ended up the following implementation. I wonder, how could I able to store user credit card information such as Uber or AirBnb. Everytime, user clicks on make a payment, and displays the credit card information entry viewcontroller.
By the way, transaction happens succesfully, and I could able to see charges on my BrainTree sandbox account.
- (IBAction)placeOrderBtnClicked:(id)sender {
[self showDropIn: TOKEN];
}
- (void)showDropIn:(NSString *)clientTokenOrTokenizationKey {
BTDropInRequest *request = [[BTDropInRequest alloc] init];
BTDropInController *dropIn = [[BTDropInController alloc] initWithAuthorization:clientTokenOrTokenizationKey request:request handler:^(BTDropInController * _Nonnull controller, BTDropInResult * _Nullable result, NSError * _Nullable error) {
if (error != nil) {
NSLog(#"ERROR");
} else if (result.cancelled) {
NSLog(#"CANCELLED");
[self dismissViewControllerAnimated:YES completion:NULL];
} else {
[self postNonceToServer:result.paymentMethod.nonce];
}
}];
[self presentViewController:dropIn animated:YES completion:nil];
}
- (void)postNonceToServer:(NSString *)paymentMethodNonce {
self.manager = [AFHTTPSessionManager manager];
NSDictionary *params = #{#"amount" : #"44", #"payment_method_nonce" : paymentMethodNonce};
manager.responseSerializer = [AFHTTPResponseSerializer serializer];
[manager POST:URLString parameters:params progress:nil success:^(NSURLSessionDataTask * _Nonnull operation, id _Nonnull responseObject) {
NSLog (#"transaction is succesfull");
} failure:^(NSURLSessionDataTask * _Nullable operation, NSError * _Nonnull error) {
}];
}
// the following method never gets called!!!
- (void)fetchExistingPaymentMethod:(NSString *)clientToken {
[BTDropInResult fetchDropInResultForAuthorization:clientToken handler:^(BTDropInResult * _Nullable result, NSError * _Nullable error) {
if (error != nil) {
NSLog(#"ERROR");
} else {
// Use the BTDropInResult properties to update your UI
NSLog(#"Payment method :%#", result.paymentMethod);
NSLog(#"Payment Description :%#", result.paymentDescription);
NSLog(#"Payment option type :%ld", (long)result.paymentOptionType);
}
}];
}
UPDATE: I want to see the following highlighted section

Answer 1

Full disclosure: I work at Braintree. If you have any further questions, feel free to contact support.
Do you mean that you want the payment form to display the stored payments or are you asking how to store the payments? In order to have the Drop-in display previously stored payment methods, you need to pass the customer_id into the ClientToken.generate() call on your server-side. If you are looking to save a payment method, then again, this would happen on your server-side call, as you would have to pass the nonce from client to server and use that nonce in a PaymentMethod.create() call.