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Code:
import DrawControl from "react-mapbox-gl-draw"; export default function MapboxGLMap() { let drawControl = null return( <DrawControl ref={DrawControl => {drawControl = DrawControl}}/> ) } I want to load data when the drawControl not null. I check the document that may use callback ref.
So, how do I listen the drawControl changes and load data?
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And since changing ref doesn't cause the component to re-render, the button stays active. To demonstrate this point further, let's add a parent component. By default when you render a React component it recursively re-renders all its children.
[2:52] In summary, useRef can be used to store data values just like useState, but the difference is that when that value changes, it doesn't cause a re-render.
Forcing an update on a React class component In any user or system event, you can call the method this. forceUpdate() , which will cause render() to be called on the component, skipping shouldComponentUpdate() , and thus, forcing React to re-evaluate the Virtual DOM and DOM state.
If you want to trigger a re-render after the ref changes, you must use useState instead of useRef. Only that way can you ensure that the component will re-render. E.g.:
function Component() { const [ref, setRef] = useState(); return <div ref={newRef => setRef(newRef)} /> } As described under useRef documentation:
Keep in mind that
useRefdoesn’t notify you when its content changes. Mutating the.currentproperty doesn’t cause a re-render. If you want to run some code when React attaches or detaches a ref to a DOM node, you may want to use a callback ref instead.
It may sometimes be better to store whatever value you are getting from the DOM node, as suggested here, instead of storing the node itself.
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