How to use Braintree V Zero on IOS app?

I am coding an IOS app with Payment feature. I decided to use Braintree V Zero.

At the very beginning, I use their excellent DropIn UI feature, and everything works fine. But when payment happen, the Drop In UI required end-user to input his credit card or Paypal information every time.

Does any expect know how to implement one automatic charge solution by BrainTree V zero?

Like Uber's charge solution.

I guess maybe need to mark the user's credit card information from app side or service side?

    router.get('/token', function (req, res) {
  console.log('Kevin in token be called %s', req.param('aCustomerId'));
  var aCustomerId = req.param('aCustomerId');
  console.log('Kevin %s', aCustomerId);
  gateway.clientToken.generate({customerId: aCustomerId}, function (error, response) {
    res.send(response.clientToken);
    console.log(response.clientToken);
  });
});

Thank you in advanced!

Solution

_{Full disclosure: I work for Braintree.}

The Braintree drop-in will display previously used payment methods for a customer, if you pass the customer_id in when generating a client token on your server. Here's an example of how to do it in Node:

gateway.clientToken.generate({
  customerId: aCustomerId
}, function (err, response) {
  var clientToken = response.clientToken
});

Once a payment method is used, it will be saved in the drop-in and the customer will not have to enter it again. Pass the token of the saved payment method when creating a transaction:

gateway.transaction.sale({
  amount: "10.00",
  paymentMethodToken: theToken,
  options: {
    submitForSettlement: true
  }
}, function (err, result) {
});

If you have any further questions, please feel free to contact Braintree support. 3133e