How to Set Text in Text Programmatically in a Function Component for React Native Form Validation

Learn how to handle form validation in React Native by setting error messages for empty fields programmatically within a function component.
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This video is based on the question https://stackoverflow.com/q/64619535/ asked by the user 'Boidurja Talukdar' ( https://stackoverflow.com/u/8565241/ ) and on the answer https://stackoverflow.com/a/64619561/ provided by the user 'Muhammad' ( https://stackoverflow.com/u/11566074/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling Form Validation in React Native

Form validation is a crucial aspect of user interface design, especially when handling user input. In React Native, ensuring that fields like mobile and password are filled out before submission is essential to enhance user experience and data integrity. In this post, we will explore a common issue related to form validation, specifically when dealing with error messages for empty fields in a React Native application.

The Problem

When building a login form, you might run into a situation where you want to display an error message if the fields for mobile and password are left empty. An attempt to set an error message in a validation function often leads to runtime errors if not handled correctly.

In this scenario, you might encounter an error stating:

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

This error occurs because the setMessage function is defined within the component but is being called in an external function outside its scope.

The Solution

To solve this problem, we can restructure the component so that the login function is defined inside the functional component. This way, it will have access to the state variables and the setMessage function from the React hooks.

Step-by-Step Guide

Move the login function into the component:
By placing the login function within the functional component, it can access the setMessage function.

Here’s the revised code for your component:

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

Optional: Exporting the login function
If you need to keep the login function outside the main component for any reason, you can pass the setMessage function as an argument:

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

Then, you would call the function as follows:

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

Conclusion

By restructuring your code to keep state management functions within the component, you can effectively handle form validation in React Native applications. This ensures that error messages are set and displayed correctly when required fields are empty. Proper form validation not only improves user experience but also ensures that you collect the necessary information to proceed with user authentication.

With this guide, you should now have a clear roadmap to implement text setting in your React Native form validation logic effectively. Happy coding!