title: Authorize a transaction with unknown amount, and charge the amount for the service later
body: <p>I'm developing a kind of Car Booking iOS Application; and I want to develop following kind of process for payment :</p>
  
  <p>Want to implement Consumption based payment for my App Users. Rather than pre-payment; User will do Post Payment based on his Usage.</p>
  
  <p>In my Application, User will book a Car ---> He can use it for as many Hours as he wants to use. E.g. he used it for 10 Hours ---> And at the time of submitting car back ---> System automatically deducts the money from his credit card for his usage.</p>
  
  <p>So, e.g. Hourly Rate is 2$/Hour and User used it for 20 hours; than system will deduct 40 $(2*20) From his credit card.</p>
  
  <p>My Plan is to Use Apple Pay,I got below information : <a href="https://developer.apple.com/apple-pay/get-started/" rel="nofollow noreferrer">https://developer.apple.com/apple-pay/get-started/</a></p>
  
  <p><code>Transaction type</code>  : Authorization unknown amount &amp; capture<br>
   <code>Description</code>       : Authorize a transaction with unknown amount, and charge<br>
                         the amount for the service later
  <br> <code>Example</code>       :  Taxi ride
  <br></p>
  
  <p>I have read apple pay document and see apple pay video from here :<br></p>
  
  <p><a href="https://developer.apple.com/videos/play/wwdc2015/702/" rel="nofollow noreferrer">https://developer.apple.com/videos/play/wwdc2015/702/</a> <br>
  <a href="https://developer.apple.com/apple-pay/get-started/" rel="nofollow noreferrer">https://developer.apple.com/apple-pay/get-started/</a> <br>
  <a href="https://dzone.com/articles/integrating-your-ios-app-apple" rel="nofollow noreferrer">https://dzone.com/articles/integrating-your-ios-app-apple</a> <bR>
  <a href="https://developer.apple.com/apple-pay/Getting-Started-with-Apple-Pay.pdf" rel="nofollow noreferrer">https://developer.apple.com/apple-pay/Getting-Started-with-Apple-Pay.pdf</a></p>
  
  <p>I have also refer following demo:<br></p>
  
  <p>I'm buildingn my iOS Application in Objective C.</p>
  
  <p><a href="https://developer.apple.com/library/content/samplecode/Emporium/Introduction/Intro.html" rel="nofollow noreferrer">https://developer.apple.com/library/content/samplecode/Emporium/Introduction/Intro.html</a> <br>
  <a href="https://github.com/prolificinteractive/applepay-demo" rel="nofollow noreferrer">https://github.com/prolificinteractive/applepay-demo</a> <br>
  <a href="https://www.raywenderlich.com/87300/apple-pay-tutorial" rel="nofollow noreferrer">https://www.raywenderlich.com/87300/apple-pay-tutorial</a>
  <br></p>
  
  <p>also refer :</p>
  
  <p><a href="https://stackoverflow.com/questions/39665659/paypal-charge-customer-an-unknown-amount-at-a-later-date">Paypal - charge customer an unknown amount at a later date</a></p>
  
  <p>Now I want to know is there any best option than apple pay? Or how can I achieve above requirement using Apple Pay.</p>
  
  <p>My main goal is to take automatic payment from user after he/she used my services.</p>
  
  <p>Please give me your opinion for the same and How can I use <code>Transaction type</code>?</p>
  
  <p>Thanks in Advance.</p>