Typescript with react-spring. Property 'interpolate' does not exists on type 'number'

Question

I use react-spring with Typescript. When I use the native rendering with react-spring I get an error message to the interpolate function.

"Property 'interpolate' does not exist on type 'number'"

I tried to introduce an interface to the Spring component inner props, but I could not get rid of the various error messages.

import * as React from 'react';
import { FC, useState } from 'react';
import { Spring, animated as a } from 'react-spring/renderprops';

interface Props {
onClick: Function;
}

/*interface SpringProps {
scale: number | Scale;
}

interface Scale {
interpolate: Function;
}*/

const SpringButton: FC<Props> = ({ onClick }) => {
const [pressed, setPressed] = useState(false);
return (
    <Spring native from={{ scale: 1 }} to={{ scale: pressed ? 0.8 : 1 }}>
    {(props /*: SpringProps*/) => (
        <a.button
        style={{
            height: '100px',
            width: '100px',
            transform: props.scale.interpolate(scale => `scale(${scale})`) 
        }}
        onMouseDown={() => setPressed(true)}
        onClick={e => {
            setPressed(false);
            onClick(e);
        }}
        onMouseLeave={() => setPressed(false)}
        >
        Click me
        </a.button>
    )}
    </Spring>
);
};

export default SpringButton;

https://codesandbox.io/s/34zopyr8zq

Answer 1

The Why

When using the render-props version of react-spring, interpolate is used a little differently than the hooks version. interpolate doesn't exist on scale because scale is just a plain old number, not an object.

The Fix

You will need to import interpolate first:

import { interpolate, Spring, animated as a } from 'react-spring/renderprops';

then style the button using the imported function:

style={{
  height: '100px',
  width: '100px',
  transform: interpolate(
    [props.scale],
    (s) => `scale(${s})`
  ),
}}