Скачать или смотреть How to Fix TypeError: Cannot read property 'state' of undefined in React Router v5.2

Learn how to resolve the common error in React Router v5.2 when trying to access props passed through Link. This post provides clear code examples and explanations.
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Fixing TypeError: Cannot read property 'state' of undefined in React Router v5.2

If you’re working with React and using React Router, you may encounter the error "TypeError: Cannot read property 'state' of undefined" when trying to access props passed through a Link. This can be frustrating, especially if you're unsure where things went wrong. In this guide, we’ll break down this problem and provide a clear solution to help you retrieve your props effectively.

Understanding the Problem

In the provided code snippet, the issue arises in the MyReserv component when attempting to access this.props.location.state.data. The error suggests that the location property is undefined, which can happen if the component is not properly set up to receive routing information.

What Causes This Error?

Not Wrapped in withRouter: The component that needs to access the routing props (like location) must be wrapped in withRouter from React Router. If it isn’t, this.props won’t contain the necessary routing information.

Incorrect Prop Passing: If the state prop isn't properly passed when redirecting via the Link, attempting to access it in the destination component will lead to undefined errors.

Steps to Resolve the Issue

Let’s go through the solution step-by-step.

Solution: Wrap Your Component with withRouter

To ensure that your component can access the router props, you need to wrap your MyReserv component with the withRouter higher-order component. This will provide MyReserv with access to this.props.location, this.props.match, and this.props.history.

Here’s how to modify your code:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Made

Imported withRouter: This is crucial. You need to import from the react-router-dom library.

Wrapped the Component: The MyReserv component is now exported after being wrapped with withRouter, allowing it to receive props related to routing.

Testing the Fix

After implementing these changes, navigate to the MyReserv page via the Go button from your ChooseReserv component as before. You should no longer see the TypeError, and the logged data in console.log(this.props.location.state.data); should reflect the data you intended to pass.

Conclusion

Encountering an error like "TypeError: Cannot read property 'state' of undefined" can be a roadblock in your React development. However, by ensuring proper component wrapping with withRouter, you can effectively solve this problem. Now you can retrieve props passed through the Link attribute without any issues.

If you found this article helpful, feel free to share your own experiences or any further questions in the comments below! Happy coding!