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HACK Implementation of the <keep-alive />
function in Vue
For React
Please also pay attention to official support <Offsreen />
in React 18.x
More stable <KeepAlive />
function with babel
pre-compilation
-
React v17+ (beta)
-
React v16+
-
Preact v10+
-
Compatible with SSR
yarn add react-activation
# or
npm install react-activation
The plugin adds a _nk
attribute to each JSX element during compilation to help the react-activation
runtime generate an unique identifier by render location base on react-node-key
.
{
"plugins": [
"react-activation/babel"
]
}
(0.11.0+) If you don't want to use Babel, it is recommended that each <KeepAlive>
declare a globally unique and invariant cacheKey
attribute to ensure the stability of the cache, as follows:
<KeepAlive cacheKey="UNIQUE_ID" />
Like the <Counter>
component in the example
// App.js
import React, { useState } from 'react'
import KeepAlive from 'react-activation'
function Counter() {
const [count, setCount] = useState(0)
return (
<div>
<p>count: {count}</p>
<button onClick={() => setCount(count => count + 1)}>Add</button>
</div>
)
}
function App() {
const [show, setShow] = useState(true)
return (
<div>
<button onClick={() => setShow(show => !show)}>Toggle</button>
{show && (
<KeepAlive>
<Counter />
</KeepAlive>
)}
</div>
)
}
export default App
3. Place the <AliveScope>
outer layer at a location that will not be unmounted, usually at the application entrance
Note: When used with react-router
or react-redux
, you need to place <AliveScope>
inside <Router>
or <Provider>
// index.js
import React from 'react'
import ReactDOM from 'react-dom'
import { AliveScope } from 'react-activation'
import App from './App'
ReactDOM.render(
<AliveScope>
<App />
</AliveScope>,
document.getElementById('root')
)
ClassComponent
works with withActivation
decorator
Use componentDidActivate
and componentWillUnactivate
to correspond to the two states of "activate" and "unactivate" respectively.
FunctionComponent
uses the useActivate
and useUnactivate
hooks respectively
...
import KeepAlive, { useActivate, useUnactivate, withActivation } from 'react-activation'
@withActivation
class TestClass extends Component {
...
componentDidActivate() {
console.log('TestClass: componentDidActivate')
}
componentWillUnactivate() {
console.log('TestClass: componentWillUnactivate')
}
...
}
...
function TestFunction() {
useActivate(() => {
console.log('TestFunction: didActivate')
})
useUnactivate(() => {
console.log('TestFunction: willUnactivate')
})
...
}
...
function App() {
...
return (
{show && (
<KeepAlive>
<TestClass />
<TestFunction />
</KeepAlive>
)}
)
}
...
-
Add the
name
attribute to the<KeepAlive>
tag that needs to control the cache. -
Get control functions using
withAliveScope
oruseAliveController
.-
drop(name): (
drop
can only be used for nodes in the cache state. If the node is not cached but needs to clear the cache state, please userefresh
)Unload the
<KeepAlive>
node in cache state by name. The name can be of typeString
orRegExp
. Note that only the first layer of content that hits<KeepAlive>
is unloaded and will not be uninstalled in<KeepAlive>
. Would not unload nested<KeepAlive>
. -
dropScope(name): (
dropScope
can only be used for nodes in the cache state. If the node is not cached but needs to clear the cache state, please userefreshScope
)Unloads the
<KeepAlive>
node in cache state by name. The name optional type isString
orRegExp
, which will unload all content of<KeepAlive>
, including all<KeepAlive>
nested in<KeepAlive>
. -
refresh(name):
Refresh the
<KeepAlive>
node in cache state by name. The name can be of typeString
orRegExp
. Note that only the first layer of content that hits<KeepAlive>
is refreshed and will not be uninstalled in<KeepAlive>
. Would not refresh nested<KeepAlive>
. -
refreshScope(name):
Refresh the
<KeepAlive>
node in cache state by name. The name optional type isString
orRegExp
, which will refresh all content of<KeepAlive>
, including all<KeepAlive>
nested in<KeepAlive>
. -
clear():
will clear all
<KeepAlive>
in the cache -
getCachingNodes():
Get all the nodes in the cache
-
...
import KeepAlive, { withAliveScope, useAliveController } from 'react-activation'
...
<KeepAlive name="Test">
...
<KeepAlive>
...
<KeepAlive>
...
</KeepAlive>
...
</KeepAlive>
...
</KeepAlive>
...
function App() {
const { drop, dropScope, clear, getCachingNodes } = useAliveController()
useEffect(() => {
drop('Test')
// or
drop(/Test/)
// or
dropScope('Test')
clear()
})
return (
...
)
}
// or
@withAliveScope
class App extends Component {
render() {
const { drop, dropScope, clear, getCachingNodes } = this.props
return (
...
)
}
}
...
Add the when
attribute to the <KeepAlive />
tag that needs to control the cache. The value is as follows
- true: Cache after uninstallation
- false: Not cached after uninstallation
<KeepAlive when={false}>
The 1th parameter indicates whether it needs to be cached at the time of uninstallation.
The 2th parameter indicates whether to unload all cache contents of <KeepAlive>
, including all <KeepAlive>
nested in <KeepAlive>
.
// For example:
// The following indicates that it is not cached when uninstalling
// And uninstalls all nested `<KeepAlive>`
<KeepAlive when={[false, true]}>
...
<KeepAlive>
...
<KeepAlive>...</KeepAlive>
...
</KeepAlive>
...
</KeepAlive>
The return value is the above Boolean
or Array
, which takes effect as described above.
The final calculation time of when
is adjusted to componentWillUnmount
lifecicle of <KeepAlive>
, the problem that most of the when
do not achieve the expected effect can be avoided.
<KeepAlive when={() => true}>
<KeepAlive when={() => [false, true]}>
Under the same parent node, <KeepAlive>
in the same location will use the same cache by default.
For example, with the following parameter routing scenario, the /item
route will be rendered differently by id
, but only the same cache can be kept.
<Route
path="/item/:id"
render={props => (
<KeepAlive>
<Item {...props} />
</KeepAlive>
)}
/>
Similar scenarios, you can use the id
attribute of <KeepAlive>
to implement multiple caches according to specific conditions.
<Route
path="/item/:id"
render={props => (
<KeepAlive id={props.match.params.id}>
<Item {...props} />
</KeepAlive>
)}
/>
<KeepAlive />
would try to detect scrollable nodes in its children
, then, save their scroll position automaticlly before componentWillUnactivate
and restore saving position after componentDidActivate
If you don't want <KeepAlive />
to do this thing, set saveScrollPosition
prop to false
<KeepAlive saveScrollPosition={false} />
If your components share screen scroll container, document.body
or document.documentElement
, set saveScrollPosition
prop to "screen"
can save sharing screen container's scroll position before componentWillUnactivate
<KeepAlive saveScrollPosition="screen" />
Pass the children
attribute of <KeepAlive />
to <AliveScope />
and render it with <Keeper />
After rendering <Keeper />
, the content is transferred to <KeepAlive />
through DOM
operation.
Since <Keeper />
will not be uninstalled, caching can be implemented.
-
<KeepAlive />
needs to pass children to<AliveScope />
, so the rendering of the real content will be slower than the normal situationWill have a certain impact on the function of strictly relying on the lifecycle order, such as getting the value of
ref
incomponentDidMount
, as followsclass Test extends Component { componentDidMount() { console.log(this.outside) // will log <div /> instance console.log(this.inside) // will log undefined } render() { return ( <div> <div ref={ref => { this.outside = ref }} > Outside KeepAlive </div> <KeepAlive> <div ref={ref => { this.inside = ref }} > Inside KeepAlive </div> </KeepAlive> </div> ) } }
The above error in
ClassComponent
can be fixed by using thewithActivation
high-level componentFunctionComponent
currently has no processing method, you can usesetTimeout
ornextTick
to delay ref getting behavior@withActivation class Test extends Component { componentDidMount() { console.log(this.outside) // will log <div /> instance console.log(this.inside) // will log <div /> instance } render() { return ( <div> <div ref={ref => { this.outside = ref }} > Outside KeepAlive </div> <KeepAlive> <div ref={ref => { this.inside = ref }} > Inside KeepAlive </div> </KeepAlive> </div> ) } }
-
Destructive impact on
Context
after
[email protected]
with[email protected]+
, this question has been automatic fixed[email protected]
withreact@17+
you Need to make the following changes to achieve automatic repairimport { autoFixContext } from 'react-activation' autoFixContext( [require('react/jsx-runtime'), 'jsx', 'jsxs', 'jsxDEV'], [require('react/jsx-dev-runtime'), 'jsx', 'jsxs', 'jsxDEV'] )
Versions below
[email protected]
need to be repaired manually, refer to the followingProblem reference: StructureBuilder/react-keep-alive#36
<Provider value={1}> {show && ( <KeepAlive> <Consumer> {( context // Since the rendering level is broken, the context cannot be obtained here. ) => <Test contextValue={context} />} </Consumer> </KeepAlive> )} <button onClick={toggle}>toggle</button> </Provider>
Choose a repair method
-
Create
Context
usingcreateContext
exported fromreact-activation
-
Fix the affected
Context
withfixContext
exported fromreact-activation
... import { createContext } from 'react-activation' const { Provider, Consumer } = createContext() ... // or ... import { createContext } from 'react' import { fixContext } from 'react-activation' const Context = createContext() const { Provider, Consumer } = Context fixContext(Context) ...
-
-
Affects the functionality that depends on the level of the React component, as follows
- Fix
withRouter/hooks
of react-router -
Error Boundaries(Fixed) -
React.Suspense & React.lazy(Fixed) - React Synthetic Event Bubbling Failure
- Other undiscovered features
- Fix