moving to using a filter function for getting the item

src/rust/core/model.rs

@@ -36,8 +36,11 @@ impl<T> Model<T> {
         Ok(())
     }
 
-    pub fn get_item(&self, index: i32) -> Option<&T> {
-        self.items.get(index as usize)
+    pub fn get_item<P>(&self, f: P) -> Option<&T>
+    where
+        P: FnMut(&&T) -> bool,
+    {
+        self.items.iter().filter(f).next()
     }
 
     pub fn insert_item(&mut self, item: T, index: i32) -> Result<()> {