     /**
     Get the hash for a URL in Watch side cache.
     
+    You can use the returned string to check whether the corresponding image is cached in watch or not, by using `WKInterfaceDevice.currentDevice().cachedImages`
+    
     :param: string The absolute string of a URL.
     
     :returns: The hash string used when cached in Watch side cache.
     */
-    public class func kf_hashForURLString(string: String) -> String {
+    public class func kf_cacheKeyForURLString(string: String) -> String {
         return string.kf_MD5()
     }
 }

                        
                        if cacheInWatch {
                            if let URLString = URL.absoluteString {
                                let key = WKInterfaceImage.kf_hashForURLString(URLString)
                                cachedInWatch = WKInterfaceDevice.currentDevice().addCachedImage(image!, name: key)
                            }
                        }

        
        let imageKey: String
        if let URLString = URL.absoluteString {
            imageKey = WKInterfaceImage.kf_cacheKeyForURLString(URLString)
        } else {
            return (false, cacheInWatch)
        }
