var demoText = GrandStore(name: "DemoText", defaultValue: ""), the second para can not be nil, GrandStore must usr it to infer the type.

demoText.Value = "the value you will set" //set the value

let va = demoText.Value //get the value

let stu = GrandStore(name: "student", defaultValue: Student())// Student is a custom cass and it must confirm NSCoding protocal.The set and get process is the same as the DemoText 

var demoCache = GrandStore(name: "CacheTest", defaultValue: "", timeout: 10)//if you want set a value which can expire,just add the timeout para. cache time 

demoCache..setCacheTime(50)// you can change the cache time anytime, or you can set a current GrandStore to cache mode

demoCache.clear()// call the clear() func to clear the cache

stu.addObserver { (observerObject, observerKey, oldValue, newValue) -> Void in
              self.lblStudent?.text = "old:\(oldValue.debugDescription), new:\(newValue.debugDescription)"
        }
        //if you want to observer the value change, just call the addObserver func, and set the block callback

stu.removeObserver() //call the removeObserver() func to remoce the observer