Formik官方應用案例解析（四）組件生命周期事件
示例工程：formik-09x-component-lifecycle-events-example
核心文件：index.js
示例說明
Formik大部分示例工程中都使用了極其方式創建Formik表單組件，本示例中則使用了復雜（或者說典型）方式創建一個Formik表單組件，即使用其繼承自React.Component組件，從而展示有關生命周期事件的基本使用。但是，也比較簡單，只涉及到了兩個事件：
-
componentWillReceiveProps
-
render
但是，這個示例中使用的componentWillReceiveProps事件在最新的React中已經過時。引用一個老外的話說是：
This lifecycle, however, is on the deprecation path; it will stop working as-named in React 17: https://reactjs.org/docs/react-component.html#unsafe_componentwillreceiveprops
Given that, we should provide a more future-friendly solution for listening for shallow route changes. Perhaps adding a popstate listener in componentDidMount. If that seems like the best option I can add it to docs, but opening this ticket for discussion/tracking.
現在，在最新版本React環境下需要使用UNSAFE_componentWillReceiveProps()來代替。
另外：在新版本中，官方明確指出使用上述事件容易導致一些復雜BUG的出現，所以官方建議使用事件來代替。另外，還有如下建議：
Note:
Using this lifecycle method often leads to bugs and inconsistencies, and for that reason it is going to be deprecated in the future.
If you need to perform a side effect (for example, data fetching or an animation) in response to a change in props, use componentDidUpdate lifecycle instead.
For other use cases, follow the recommendations in this blog post about derived state.
If you used componentWillReceiveProps for re-computing some data only when a prop changes, use a memoization helper instead.
If you used componentWillReceiveProps to “reset” some state when a prop changes, consider either making a component fully controlled or fully uncontrolled with a key instead.
In very rare cases, you might want to use the getDerivedStateFromProps lifecycle as a last resort.
引用
1，https://github.com/zeit/next.js/issues/4154
2，https://reactjs.org/docs/react-component.html#unsafe_componentwillreceiveprops
Formik官方應用案例解析（四）組件生命周期事件