ipad app -wcf ,webservices and consuming by objective c using ODATA protocol

Hello,
I am new to apple development. I want to write an app to make ipad to get/post to SQL Server. I researched and decided to go with the OData web service way. I have written a web service and need to get it to be consumed by ipad. For that i need to create a proxy class. There are more steps in the process, but this is one of the steps i am stuck. I cannot create the proxy.
When i try to create proxy class it throws me error saying no such file or directory.
So if this is not the correct place to ask these development questions can you re-direct me?
Thanks in advance.