How can React-native's form data be updated?

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React Native's form data can be updated by implementing controlled components. Controlled components are those components that render form elements and accept user input as props, and handle user input changes by updating the state within the component.

To update form data in React Native, follow these steps:

1. Define the state object in the component constructor. This object will hold the current values of the form fields.

constructor(props) {
  super(props);
  this.state = {
    firstname: '',
    lastname: '',
    email: '',
    password: '',
  };
}

1. Create input elements in the render method and bind each input field to the corresponding state property.

<TextInput
  placeholder="Enter your first name"
  value={this.state.firstname}
  onChangeText={(text) => this.setState({ firstname: text })}
/>

1. Define a function to handle form submission. This function should retrieve the form data from the state and submit it to the server.

handleSubmit() {
  const { firstname, lastname, email, password } = this.state;
  // Submit form data to the server
}

1. Attach the handleSubmit function to the form submit button.

<Button title="Submit" onPress={() => this.handleSubmit()} />

When the user enters data into the form fields, the state will be updated accordingly. The handleSubmit function can then retrieve the form data from the state and submit it to the server.