fix: don't create a new component every time

Author: satya164

README.md

@@ -223,6 +223,7 @@ renderScene = ({ route }) => {
 
 Where `<HomeComponent />` is a `PureComponent`.
 
+If you are using the `SceneMap` helper, the scenes are already optimized with `PureComponent` and won't re-render if parent's state changes.
 
 ### Avoid one frame delay
 

src/SceneMap.js

@@ -3,14 +3,12 @@
 import React, { PureComponent } from 'react';
 
 export default function SceneMap(scenes: { [key: string]: Function }) {
-  return ({ route }: *) => {
-    class SceneComponent extends PureComponent {
-      static displayName = `SceneMap(${route.key})`;
-
-      render() {
-        return React.createElement(scenes[route.key], this.props);
-      }
+  class SceneComponent extends PureComponent<void, *, void> {
+    render() {
+      /* eslint-disable react/prop-types */
+      return React.createElement(scenes[this.props.route.key], this.props);
     }
-    return <SceneComponent key={route.key} route={route} />;
-  };
+  }
+
+  return ({ route }: *) => <SceneComponent key={route.key} route={route} />;
 }