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Change in unmounting timing from React 15
See original GitHub issueDo you want to request a feature or report a bug?
Question (could be a bug)
What is the current behavior?
In React 15 if you replace a component with another one, the old component has componentWillUnmount called before the new component has componentWillMount called. However, this has changed in React 16. Now the new component has componentWillMount called before the old component has had its componentWillUnmount called.
What is the expected behavior?
I would have expected that the React 15 behaviour would have been maintained. It seems strange to me that new components are starting to be mounted before an old component has unmounted.
Issue Analytics
- State:
- Created 5 years ago
- Comments:6 (1 by maintainers)
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According to the React 16.0 docs indeed this is not considered a bug. I’ve made a few changes on your initial
React 16 examplehttps://codesandbox.io/s/n3x14rr7ylYou can see that
B.componentDidMountwill be called afterA.componentWillUnmount, which make sense… before mounting a new component React will “prepare” the new one.Edit: This is why they also recommend to make API calls on
componentDidMount.componentWillMountcan be called multiple times in because fiber can suspend tasks and prioritise others.Cheers @gaearon. It makes sense when looking at it like that. My intuition led me to expect otherwise.