How to implement Braintree client for card payment in iOS Swift

First of all you need to add Braintree framework into your project. add pod 'Braintree/Card' in podfile of your project.

now import Braintree in file in which  you want to collect card details.

  import Braintree

declare the BTAPIClient instance as :

 var braintreeAPIClient: BTAPIClient?

now you need to obtain a client Token from your backend server, your backend server is responsible for genrating a clientToken by Braintree server side SDK.

so before initialization of  BTAPIClient make sure you have obtained  the clientToken.

now intialize the BTAPIClient instance as:

  braintreeAPIClient = BTAPIClient(authorization: clientToken)! 
 //clientToken must obtain from backend server before initialization

now create a BTCardClient instance

let cardClient = BTCardClient(APIClient: braintreeAPIClient!)

now you need to need to instantiate a BTCard , BTCard represents the credit card data of customer and serve as input for tokenization.

let braintreeCard = BTCard(number: creditCardNumber, expirationMonth: expiryMonth, expirationYear: expiryYear, cvv: cvvNumber)

now tokenize the BTCard with  BTCARDClient as :

 cardClient.tokenizeCard(braintreeCard) { (tokenizedCard, error) in
       // tokenizedCard!.nonce genrated here can be send to your backend server and further processing take place at backend server.
     }

 send  resulting tokenizedCard!.nonce  to your backend server.

Thanks,