**Course Title:** Building Mobile Applications with React Native **Section Title:** Performance Optimization Techniques **Topic:** Optimizing rendering with PureComponent and memo As we continue to build high-performance mobile applications with React Native, it's essential to optimize rendering to ensure a seamless user experience. In this topic, we'll explore two powerful techniques to optimize rendering: `PureComponent` and `memo`. ### What is Optimization? Optimization is the process of making your application faster, more efficient, and more responsive. In the context of React Native, optimization involves reducing the number of unnecessary re-renders, minimizing the time it takes to render components, and improving the overall performance of your application. ### What is PureComponent? `PureComponent` is a built-in React component that helps optimize rendering by reducing the number of unnecessary re-renders. When a `PureComponent` is updated, React will only re-render it if the props or state have changed. This is achieved by using a shallow comparison of the props and state. ```jsx import React, { PureComponent } from 'react'; class MyPureComponent extends PureComponent { render() { return <Text>Hello World!</Text>; } } ``` ### What is memo? `memo` is a higher-order component (HOC) that helps optimize rendering by caching the results of expensive function calls. When a component is wrapped with `memo`, React will only re-render it if the props have changed. ```jsx import React, { memo } from 'react'; const MyMemoComponent = memo(() => { // expensive function call const data = fetchDataFromAPI(); return <Text>{data}</Text>; }); ``` ### When to Use PureComponent and memo? Use `PureComponent` when: * You have a component with a large number of props or state that rarely change. * You want to reduce the number of unnecessary re-renders. Use `memo` when: * You have a component with an expensive function call that rarely changes. * You want to cache the results of the function call to improve performance. ### Example Use Case Suppose we have a component that fetches data from an API and displays it in a list. We can use `memo` to cache the results of the API call and reduce the number of unnecessary re-renders. ```jsx import React, { memo } from 'react'; import { FlatList } from 'react-native'; const MyComponent = memo(() => { const [data, setData] = useState([]); const fetchData = async () => { const response = await fetch('https://api.example.com/data'); const jsonData = await response.json(); setData(jsonData); }; useEffect(() => { fetchData(); }, []); return ( <FlatList data={data} renderItem={({ item }) => <Text>{item.name}</Text>} keyExtractor={(item) => item.id.toString()} /> ); }); ``` ### Best Practices * Use `PureComponent` and `memo` sparingly, as overusing them can lead to performance issues. * Use `PureComponent` when the props or state rarely change, and use `memo` when the function call rarely changes. * Avoid using `PureComponent` and `memo` on components with complex logic or multiple dependencies. ### Conclusion In this topic, we've explored two powerful techniques to optimize rendering in React Native: `PureComponent` and `memo`. By using these techniques, we can reduce the number of unnecessary re-renders, minimize the time it takes to render components, and improve the overall performance of our application. Remember to use `PureComponent` and `memo` sparingly and follow best practices to ensure optimal performance. ### Additional Resources * [React documentation on PureComponent](https://reactjs.org/docs/react-api.html#purecomponent) * [React documentation on memo](https://reactjs.org/docs/react-api.html#memo) * [React Native documentation on optimization](https://reactjs.org/docs/optimizing-performance.html) ### Leave a comment or ask for help Do you have any questions or need further clarification on any of the concepts covered in this topic?