Troubleshooting React/TypeScript

React/TypeScript: Troubleshooting Context Consumption with Higher-Order Component (HOC)

If you’re working with React and TypeScript, you might encounter difficulties when trying to implement context consumption with a Higher-Order Component (HOC). In this blog post, we will guide you through the process of troubleshooting this issue, specifically in React 16.3 and TypeScript 2.8.

Understanding the Problem

Before diving into the solution, let’s understand the problem at hand. The React documentation provides an example of consuming context with a HOC. The code snippet from their manual looks like this:

const ThemeContext = React.createContext('light');

export function withTheme(Component) {
  return function ThemedComponent(props) {
    return (
      <ThemeContext.Consumer>
        {theme => <Component {...props} theme={theme} />}
      </ThemeContext.Consumer>
    );
  };
}

Now, when you try to implement this example in TypeScript, you might encounter an error with the following line:

export default withTheme(ThemedButton);

The TypeScript compiler complains with the following message:

Argument of type 'typeof ThemedButton' is not assignable to parameter of type 'new () => Component<ThemedButtonProps, ThemedButtonState, any>'

This error occurs because the types do not match correctly and can lead to frustration. Let’s move on to the solution to resolve this issue.

The Solution

To fix the problem, we need to make a few adjustments to the code. First, instead of using Component, we will use React.ComponentType<Props> to accept both class components and functional components. This modification ensures the compatibility of signatures.

Here’s the updated withTheme function:

export function withTheme<P extends ThemeAwareProps>(Component: React.ComponentType<P>) {
  return function ThemedComponent(props: Pick<P, Exclude<keyof P, keyof ThemeAwareProps>>) {
    return (
      <ThemeContext.Consumer>
        {theme => <Component {...props} theme={theme} />}
      </ThemeContext.Consumer>
    );
  };
}

In addition, you need to make a small modification to the ThemedButton component. Instead of extending React.Component without specifying any props and state, you should define the props and state types explicitly.

interface ThemedButtonProps extends ThemeAwareProps {
}

interface ThemedButtonState {
}

class ThemedButton extends React.Component<ThemedButtonProps, ThemedButtonState> {
  // ...
}

With these adjustments, the error should be resolved, and you can consume the context using the HOC as intended.

Conclusion

In this blog post, we discussed how to troubleshoot the issue of context consumption with a Higher-Order Component (HOC) in React and TypeScript. By following the provided solution and making the necessary adjustments, you should now be able to successfully consume context using the HOC pattern in your React application. Happy coding!

References:
– React Documentation: Consuming Context with a HOC
– Dev.to: TypeScript, React, and HOCs

reference : 

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