How to pass ref to draw control in react-map-gl - reactjs

Question

Following the Mapbox draw example I can use the draw variable to access all features that are drawn on a map.
const draw = new MapboxDraw({
// ...
});
map.addControl(draw);
// ...
function updateArea(e) {
const data = draw.getAll(); // Accessing all features (data) drawn here
// ...
}
However, in react-map-gl library useControl example I can not figure out how to pass ref to the DrawControl component so I can use it as something like draw.current in a similar way as I did draw in normal javascript above.
In my DrawControl.jsx
const DrawControl = (props) => {
useControl(
({ map }) => {
map.on('draw.create', props.onCreate);
// ...
return new MapboxDraw(props);
},
({ map }) => {
map.off('draw.create', props.onCreate);
// ...
},{
position: props.position,
},
);
return null;
};
In my MapDrawer.jsx
import Map from 'react-map-gl';
import DrawControl from './DrawControl';
// ...
export const MapDrawer = () => {
const draw = React.useRef(null);
const onUpdate = React.useCallback((e) => {
const data = draw.current.getAll(); // this does not work as expected
// ...
}, []);
return (
// ...
<Map ...>
<DrawControl
ref={draw}
onCreate={onUpdate}
onUpdate={onUpdate}
...
/>
</Map>
)
}
I also get an error stating I should use forwardRef but I'm not really sure how.
react_devtools_backend.js:3973 Warning: Function components cannot be given refs. Attempts to access this ref will fail. Did you mean to use React.forwardRef()?
What I need is basically to delete the previous feature if there is a new polygon drawn on a map so that only one polygon is allowed on a map. I want to be able to do something like this in the onUpdate callback.
const onUpdate = React.useCallback((e) => {
// ...
draw.current.delete(draw.current.getAll.features[0].id);
// ...
}, []);

Answer 1

I had the similar problem recently with that lib, I solved it doing the following :
export let drawRef = null;
export default const DrawControl = (props) => {
drawRef = useControl(
({ map }) => {
map.on('draw.create', props.onCreate);
// ...
return new MapboxDraw(props);
},
({ map }) => {
map.off('draw.create', props.onCreate);
// ...
},{
position: props.position,
},
);
return null;
};
import DrawControl, {drawRef} from './DrawControl';
// ...
export const MapDrawer = () => {
const draw = drawRef;
const onUpdate = React.useCallback((e) => {
const data = draw?draw.current.getAll():null; // this does not work as expected
// ...
}, []);
return (
// ...
<Map ...>
<DrawControl
onCreate={onUpdate}
onUpdate={onUpdate}
...
/>
</Map>
)
}
const onUpdate = React.useCallback((e) => {
// ...
drawRef.delete(drawRef.getAll.features[0].id);
// ...
}, []);
Once component created, the ref is available for use.
Not that elegant but working... Sure there might be cleaner way...
Hope that helps!
Cheers

Answer 2

Pass draw from draw control to parent component.
const DrawControl = (props) => {
const [draw, setDraw] = useState()
const { setDraw: setDrawInParent, onUpdate, onCreate, onDelete } = props;
useEffect(() => {
if (draw) setDrawInParent(draw)
}, [draw])
useControl(
({ map }) => {
map.on("draw.create", onCreate);
map.on("draw.update", onUpdate);
map.on("draw.delete", onDelete);
const draw = new MapboxDraw(props);
setDraw(draw);
return draw;
}
);
return null;
};

Answer 3

I think I found a better solution combine forwardRef and useImperativeHandle to solve:
export const DrawControl = React.forwardRef((props: DrawControlProps, ref) => {
const drawRef = useControl<MapboxDraw>(
() => new MapboxDraw(props),
({ map }) => {
map.on("draw.create", props.onCreate);
map.on("draw.update", props.onUpdate);
map.on("draw.delete", props.onDelete);
map.on("draw.modechange", props.onModeChange);
},
({ map }) => {
map.off("draw.create", props.onCreate);
map.off("draw.update", props.onUpdate);
map.off("draw.delete", props.onDelete);
map.off("draw.modechange", props.onModeChange);
},
{
position: props.position,
}
);
React.useImperativeHandle(ref, () => drawRef, [drawRef]); // This way I exposed drawRef outside the component
return null;
});
in the component:
const drawRef = React.useRef<MapboxDraw>();
const [drawMode, setDrawMode] = React.useState<DrawMode>(“draw_polygon");
const changeModeTo = (mode: DrawMode) => {
// If you programmatically invoke a function in the Draw API, any event that directly corresponds with that function will not be fired
drawRef.current?.changeMode(mode as string);
setDrawMode(mode);
};
<>
<DrawControl
ref={drawRef}
position="top-right”
displayControlsDefault={false}
controls={{
polygon: true,
trash: true,
}}
defaultMode=“draw_polygon"
onCreate={onUpdate}
onUpdate={onUpdate}
onDelete={onDelete}
onModeChange={onModeChange}
/>
<button
style={{
position: ‘absolute’,
left: ‘20px’,
top: ‘20px’,
backgroundColor: '#ff0000’,
}}
onClick={() => changeModeTo('simple_select’)}
>
Change to Simple Select
</button>
<>