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An update on async rendering #596

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Mar 27, 2018
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544c0bc
Migrated async update from Quip to Markdown
bvaughn Feb 6, 2018
e298b47
Wordsmithing
bvaughn Feb 6, 2018
9ff0f12
Split StrictMode into its own top level docs page
bvaughn Feb 6, 2018
0674c34
Added string ref section to strict mode page
bvaughn Feb 6, 2018
cdb4b9e
Added TOC header links to Strict Mode page
bvaughn Feb 6, 2018
289a2da
Prettier
bvaughn Feb 6, 2018
99fedea
Wording changes in response to PR feedback
bvaughn Feb 6, 2018
49464f7
Removed some unnecessary parens
bvaughn Feb 6, 2018
fe6b133
Add Dan as an author to "Update on Async"
bvaughn Feb 6, 2018
1314117
Wording improvements in response to Dan's feedback
bvaughn Feb 7, 2018
f005c04
Wordsmithing
bvaughn Feb 7, 2018
06d5be4
Prettier
bvaughn Feb 7, 2018
3696388
Increased Prettier line-width for examples
bvaughn Feb 7, 2018
ac23b1f
Trigger Netlify rebuild
bvaughn Feb 7, 2018
5cae7c6
Strict Mode blog title capitalization
bvaughn Feb 7, 2018
f70c0dd
Minor wordsmithing
bvaughn Feb 7, 2018
c1e67be
Wordsmithing in response to PR feedback
bvaughn Feb 12, 2018
75a43aa
Wordsmithing in response to PR feedback
bvaughn Feb 12, 2018
fb3b91f
Add explanation for render and commit lifecycles
bvaughn Feb 12, 2018
60d65ce
Wordsmithing
bvaughn Feb 12, 2018
f632f22
Wording changes for update-on-async and strict-mode
bvaughn Feb 13, 2018
626ac42
Moved StrictMode to docs rather than blog post
bvaughn Feb 13, 2018
7456327
Combined notes about react-lifecycles-compat
bvaughn Feb 13, 2018
2909738
Address more Sophie feedback
bvaughn Feb 13, 2018
5400338
Updated data-fetching example to show cWRP too
bvaughn Feb 13, 2018
813be17
Updated docs/recipes in response to a new GH question
bvaughn Feb 14, 2018
8de7dc4
Updated recipes to show updating/removing subscriptions
bvaughn Feb 16, 2018
c45fb40
Triggering rebuild of Netlify
bvaughn Feb 21, 2018
858c1a7
Fixed small error in example
bvaughn Feb 21, 2018
98d5a09
Added gDSFP to example
bvaughn Feb 21, 2018
442591c
Added example of updating subscription from props
bvaughn Feb 22, 2018
b1ce572
Typo
bvaughn Feb 23, 2018
2312173
Moved updating-subscription example into an external Gist with a note
bvaughn Feb 28, 2018
16eb646
Fixed typo
bvaughn Feb 28, 2018
4d16523
Typo
bvaughn Feb 28, 2018
9905159
Merge branch 'master' into update-on-async-rendering
bvaughn Mar 7, 2018
1ca6cfc
Moved async update blog post to a later, random date
bvaughn Mar 7, 2018
7408e07
Remoaved 'What can asynchronous rendering do?' section and instead li…
bvaughn Mar 7, 2018
3c75def
Deleted StrictMode and examples/images
bvaughn Mar 7, 2018
55650fc
Added explicit null value in state initializer
bvaughn Mar 15, 2018
97a109d
Added a note about experimental class properties usage in examples
bvaughn Mar 15, 2018
21fa116
Removed StrictMode from side nav
bvaughn Mar 16, 2018
92cf72d
Hardened wording a bit around async
bvaughn Mar 20, 2018
fa34fcf
16.4 -> 16.x
bvaughn Mar 22, 2018
b3bf0bd
Added getSnapshotBeforeUpdate recipe
bvaughn Mar 23, 2018
254fc8b
Wordsmithing nits
bvaughn Mar 23, 2018
b0c22f7
Wording tweak
bvaughn Mar 23, 2018
558d576
Reworked introduction
bvaughn Mar 24, 2018
7425aed
Typofix
bvaughn Mar 24, 2018
65b1496
Typo
bvaughn Mar 24, 2018
6eae811
Tweaks to async post
gaearon Mar 24, 2018
a2139de
Add a note about suspense
gaearon Mar 24, 2018
030980e
Merge pull request #6 from gaearon/tweaks-async-post
bvaughn Mar 24, 2018
e110ac5
Added a small TOC for examples
bvaughn Mar 24, 2018
ce060eb
Imported theme style tweaks from PR 587
bvaughn Mar 24, 2018
e143823
Added create-subscription example
bvaughn Mar 24, 2018
65eca09
Tweaks
bvaughn Mar 25, 2018
a3ea63a
Merge branch 'master' into update-on-async-rendering
bvaughn Mar 27, 2018
7ced9ce
Renamed blog post
bvaughn Mar 27, 2018
7cf5b58
Wordsmithing
bvaughn Mar 27, 2018
9f72403
Updated gradual migration note
bvaughn Mar 27, 2018
712f4de
Changed wording about app developer to React app developer
bvaughn Mar 27, 2018
4610392
Changes in response to Sophie's feedback
bvaughn Mar 27, 2018
b824bd2
Added getSnapshotBeforeUpdate to the polyfill notes
bvaughn Mar 27, 2018
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20 changes: 10 additions & 10 deletions content/blog/2018-03-15-update-on-async-rendering.md
Original file line number Diff line number Diff line change
Expand Up @@ -3,27 +3,27 @@ title: Update on Async Rendering
author: [bvaughn]
---

For the past few months, the React team has been working on [asynchronous rendering](/blog/2018/03/01/sneak-peek-beyond-react-16.html), and we are very excited about the new features it enables.
For over a year, the React team has been working to implement asynchronous rendering. Last month during his talk at JSConf Iceland, [Dan unveiled some of the exciting new possibilities async rendering unlocks](/blog/2018/03/01/sneak-peek-beyond-react-16.html). Now we'd like to share with you some of the lessons we've learned while working on this feature, and some suggestions we have for preparing your components to be ready for async rendering when it launches.

Along the way, we've learned that some of our legacy component lifecycles tend to encourage unsafe coding practices. They are:
One of the biggest lesson we've learned is that some of our legacy component lifecycles tend to encourage unsafe coding practices. They are:
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"lessons"?

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I proof read this several times 😭


* `componentWillMount`
* `componentWillReceiveProps`
* `componentWillUpdate`

These lifecycle methods have often been misunderstood and subtly misused; furthermore, we anticipate that these potential problems may be more prominent with async rendering. Because of this, we are adding an "UNSAFE_" prefix to these lifecycles in a future release.
These lifecycle methods have often been misunderstood and subtly misused; furthermore, we anticipate that their potential misuse may be more problematic with async rendering. Because of this, we will be adding an "UNSAFE_" prefix to these lifecycles in an upcoming release.

[React follows semantic versioning](/blog/2016/02/19/new-versioning-scheme.html), so the migration path will be gradual:
[React follows semantic versioning](/blog/2016/02/19/new-versioning-scheme.html), so this change will be gradual. Our current plan is:

* **16.3**: Introduce aliases for the unsafe lifecycles, `UNSAFE_componentWillMount`, `UNSAFE_componentWillReceiveProps`, and `UNSAFE_componentWillUpdate`. (Both the old lifecycle names and the new aliases will work in this release.)
* **16.x**: Enable deprecation warning for `componentWillMount`, `componentWillReceiveProps`, and `componentWillUpdate`. (Both the old lifecycle names and the new aliases will work in this release.)
* **17.0**: Remove `componentWillMount`, `componentWillReceiveProps`, and `componentWillUpdate` . (Only the new "UNSAFE_" lifecycle names will work in this release.)
* **16.x**: Enable deprecation warning for `componentWillMount`, `componentWillReceiveProps`, and `componentWillUpdate`. (Both the old lifecycle names and the new aliases will work in this release, but the old names will log a DEV-mode warning.)
* **17.0**: Remove `componentWillMount`, `componentWillReceiveProps`, and `componentWillUpdate` . (Only the new "UNSAFE_" lifecycle names will work from this point forward.)

In this post, we will explore some of the potential capabilities of async rendering, and we'll outline a migration plan for components that rely on these legacy lifecycles.
Below, we will outline a migration plan for components that rely on these legacy lifecycles.

## Updating class components

#### If you're an application developer, **you don't have to do anything about the legacy methods yet**. The primary purpose of the upcoming version 16.3 is to enable open source project maintainers to update their libraries in advance of any deprecation warnings. Those warnings will be enabled with a future 16.x release.
#### If you're an application developer, **you don't have to do anything about the legacy methods yet**. The primary purpose of the upcoming version 16.3 release is to enable open source project maintainers to update their libraries in advance of any deprecation warnings. Those warnings will not be enabled until a future 16.x release.

However, if you'd like to start using the new component API (or if you're a maintainer looking to update your library in advance) here are a few examples that we hope will help you to start thinking about components a bit differently. Over time, we plan to add additional "recipes" to our documentation that show how to perform common tasks in a way that avoids the problematic lifecycles.

Expand All @@ -35,9 +35,9 @@ Before we begin, here's a quick overview of the lifecycle changes planned for ve

`embed:update-on-async-rendering/new-lifecycles-overview.js`

The new static `getSnapshotBeforeUpdate` lifecycle is invoked after a component is instantiated as well as when it receives new props. It should return an object to update `state`, or `null` to indicate that the new `props` do not require any `state` updates.
The new static `getSnapshotBeforeUpdate` lifecycle is invoked after a component is instantiated as well as when it receives new props. It can return an object to update `state`, or `null` to indicate that the new `props` do not require any `state` updates.
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Real stupid question: shouldn't this line be getDerivedStateFromProps ?

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Yes, thanks!


The new `getSnapshotBeforeUpdate` lifecycle gets called right before mutations are made (e.g. before the DOM is updated). The return value for this lifecycle will be passed as the third parameter to `componentDidUpdate`.
The new `getSnapshotBeforeUpdate` lifecycle is called right before mutations are made (e.g. before the DOM is updated). The return value for this lifecycle will be passed as the third parameter to `componentDidUpdate`.

We'll look at examples of how both of these lifecycles can be used below.

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