You can declare the server URL in the RhoConfig.xml file as a property. And later, retrive the property value during the API calls.
So to delare the property in RhoConfig.xml, you need to add it as such,
start_path = '/app'
options_path = '/app/Settings'
server_URL = 'http://somedomain.com/API/'
Now in the Controller to get the value of the server_URL, you need to call the Rho::RhoConfig class and use it as like below,
if Rho::RhoConfig.exists?('server_URL')
$server_url = Rho::RhoConfig.server_URL
end
This makes the url to change on one place if required.