pre-defined config variables

Hello guys,

am new to sencha Extjs ,

i'm consuming rest web-services from my backend, in the model i have the proxy url like this :

"http://ift.tt/1Fb4Np2; , in my case the IP of the backend server is not fixed,

can i set the url to "{prefix}/get/grades" and then define the prefix variable somehow ?

thanks in advance :)

am using ext-5.1.0

pre-defined config variables