元素隐式具有“任何”类型，因为类型“字符串”的表达式不能用于索引类型“调色板”

Question

I'm getting

Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'Palette'.
  No index signature with a parameter of type 'string' was found on type 'Palette'.ts(7053)

While trying to use a list of strings to get themes from the ThemeProvider from Material-UI

swatches is a string[] and contains strings that looks like "primary.light" or "secondary.dark"

useTheme uses this file:

import { createTheme, responsiveFontSizes } from '@mui/material/styles';
    import { deepPurple, amber } from '@mui/material/colors';
    
    // Create a theme instance.
    let theme = createTheme({
      palette: {
        primary: deepPurple,
        secondary: amber,
      },
    });
    
    theme = responsiveFontSizes(theme);
    
    export default theme;

and the component:

const ColorPaletteContent = ({ content }: { content: ColorPalette }) => {
  const theme = useTheme();
  return (
    <>
      <h1>{content.title}</h1>
      <div className={colorPaletteStyles.swatch_container}>
        {content.swatches.map((swatch) => {
          const parentColor = swatch.split('.')[0];
          const childColor = swatch.split('.')[1];
          return (
            <div key={swatch} className={colorPaletteStyles.swatch}>
              <Avatar
                sx={{
                  bgcolor: theme.palette[parentColor][childColor],
                  height: 68,
                  width: 68,
                }}
              >
                {''}
              </Avatar>
              {childColor}
            </div>
          );
        })}
      </div>
    </>
  );
};

The Palette interface looks like this, so I know that using a string as key here is invalid, but how do I cast my parentColor and childColor accordingly so that the type is correct?:

export interface Palette {
  common: CommonColors;
  mode: PaletteMode;
  contrastThreshold: number;
  tonalOffset: PaletteTonalOffset;
  primary: PaletteColor;
  secondary: PaletteColor;
  error: PaletteColor;
  warning: PaletteColor;
  info: PaletteColor;
  success: PaletteColor;
  grey: Color;
  text: TypeText;
  divider: TypeDivider;
  action: TypeAction;
  background: TypeBackground;
  getContrastText: (background: string) => string;
  augmentColor: (options: PaletteAugmentColorOptions) => PaletteColor;
}

Answer 1

parentColor is any , not a keyof Palette . To remove the error, you need to assert it with the correct type:

// "primary" | "secondary" | "error" | "warning" | "info" | "success"
type PaletteKey = keyof {
  [Key in keyof Palette as Palette[Key] extends PaletteColor ? Key : never]: true;
}

// "light" | "dark" | "main" | "contrastText"
type PaletteColorKey = keyof PaletteColor

theme.palette[parentColor as PaletteColorKey][childColor as PaletteColorKey]