If using the new style context, re-declare this in your class to be the
React.ContextType of your static contextType.
Should be used with type annotation or static contextType.
static contextType = MyContext
// For TS pre-3.7:
context!: React.ContextType<typeof MyContext>
// For TS 3.7 and above:
declare context: React.ContextType<typeof MyContext>
Readonly propsPrivate slotStatic Optional contextIf set, this.context will be set at runtime to the current value of the given Context.
Usage:
type MyContext = number
const Ctx = React.createContext<MyContext>(0)
class Foo extends React.Component {
static contextType = Ctx
context!: React.ContextType<typeof Ctx>
render () {
return <>My context's value: {this.context}</>;
}
}
Optional UNSAFE_Called immediately before mounting occurs, and before Component#render.
Avoid introducing any side-effects or subscriptions in this method.
This method will not stop working in React 17.
Note: the presence of getSnapshotBeforeUpdate or getDerivedStateFromProps prevents this from being invoked.
16.3, use componentDidMount or the constructor instead
Optional UNSAFE_Called when the component may be receiving new props. React may call this even if props have not changed, so be sure to compare new and existing props if you only want to handle changes.
Calling Component#setState generally does not trigger this method.
This method will not stop working in React 17.
Note: the presence of getSnapshotBeforeUpdate or getDerivedStateFromProps prevents this from being invoked.
16.3, use static getDerivedStateFromProps instead
Optional UNSAFE_Called immediately before rendering when new props or state is received. Not called for the initial render.
Note: You cannot call Component#setState here.
This method will not stop working in React 17.
Note: the presence of getSnapshotBeforeUpdate or getDerivedStateFromProps prevents this from being invoked.
16.3, use getSnapshotBeforeUpdate instead
Optional componentCatches exceptions generated in descendant components. Unhandled exceptions will cause the entire component tree to unmount.
Optional componentCalled immediately after updating occurs. Not called for the initial render.
The snapshot is only present if getSnapshotBeforeUpdate is present and returns non-null.
Optional snapshot: anyOptional componentCalled immediately before mounting occurs, and before Component#render.
Avoid introducing any side-effects or subscriptions in this method.
Note: the presence of getSnapshotBeforeUpdate or getDerivedStateFromProps prevents this from being invoked.
16.3, use componentDidMount or the constructor instead; will stop working in React 17
Optional componentCalled when the component may be receiving new props. React may call this even if props have not changed, so be sure to compare new and existing props if you only want to handle changes.
Calling Component#setState generally does not trigger this method.
Note: the presence of getSnapshotBeforeUpdate or getDerivedStateFromProps prevents this from being invoked.
16.3, use static getDerivedStateFromProps instead; will stop working in React 17
Optional componentCalled immediately before rendering when new props or state is received. Not called for the initial render.
Note: You cannot call Component#setState here.
Note: the presence of getSnapshotBeforeUpdate or getDerivedStateFromProps prevents this from being invoked.
16.3, use getSnapshotBeforeUpdate instead; will stop working in React 17
Optional getRuns before React applies the result of render to the document, and
returns an object to be given to componentDidUpdate. Useful for saving
things such as scroll position before render causes changes to it.
Note: the presence of getSnapshotBeforeUpdate prevents any of the deprecated lifecycle events from running.
Optional callback: (() => void)Optional shouldCalled to determine whether the change in props and state should trigger a re-render.
Component always returns true.
PureComponent implements a shallow comparison on props and state and returns true if any
props or states have changed.
If false is returned, Component#render, componentWillUpdate
and componentDidUpdate will not be called.
UseSignal provides a way to hook up a Lumino signal to a React element, so that the element is re-rendered every time the signal fires.
It is implemented through the "render props" technique, using the
childrenprop as a function to render, so that it can be used either as a prop or as a child of this element https://reactjs.org/docs/render-props.htmlExample as child:
Example as prop: