How to access custom field of standard/custom object of salesforce

Hi,

I am communicating with salesforce from my ROR app and it works fine
with standard fields. But while accessing any custom field of
standard/custom object of salesforce, I am getting below error:

undefined method `VisitDate' for #<Salesforce::VisitorReport:0x28d41e0>

Here VisitDate is custom field and VisitorReport is custom object of
Salesforce org.

Please help me to solve this issue.