How to access child component values from the parent in react native? - react-native

Question

I have a login screen with following structure:
import Logo from '../components/Logo'
import Form from '../components/Form';
export default class Login extends React. Component {
<View style={styles.container} >
<Logo/>
<Form type="login"/>
<View style={styles.signUpTextCont}>
...
</View>
</View>
and here is my Form component:
export default class Form extends React.Component {
constructor (props){
super(props)
this.state = {
username : '',
password : ''
}
}
handleChangeUsername = (text) => {
this.setState({ username: text })
}
handleChangePassword = (text) => {
this.setState({ password: text })
}
render() {
return (
<View style={styles.container} >
<TextInput
ref={(input) => { this.username = input }}
onChangeText = {this.handleChangeUsername}
value = {this.state.username}
/>
<TextInput
ref={(input) => { this.password = input }}
onChangeText = {this.handleChangePassword}
value = {this.state.password}
/>
<TouchableOpacity style={styles.button}>
<Text style={styles.buttonText}>{this.props.type}</Text>
</TouchableOpacity>
</View>
);
}
}
now I would like to have a checkLogin() method in Login screen (parent).
How can I access username and password values to check them in the Login screen?
I will be grateful if someone could help.

Answer 1

Try using ref keyword for accessing the child values.
<View style={styles.container} >
<Logo/>
<Form type="login"
ref={'login'}/>
<View style={styles.signUpTextCont}>
...
</View>
</View>
To Acess Child Component Values in parent:
onClick = () =>{
//you can access properties on child component by following style:
let userName = this.refs['login'].state.username;
let password = this.refs['login'].state.password;
}

Answer 2

you can use callback to send username and password to parent like this sample code:
Form:
handleChangeUsername = (text) => {
this.setState({ username: text })
this.props.userChange(text)
}
handleChangePassword = (text) => {
this.setState({ password: text })
this.props.passChange(text)
}
login:
add two state named user and pass and:
setUser = (text) => {
this.setState({user:text})
}
setPass = (text) => {
this.setState({pass:text})
}
checkLogin = () => {
// check user and pass state...
}
<Form
type="login"
userChange = {(text) => { this.setUser(text) } }
passChange = {(text) => { this.setPass(text) } }
/>
and now, user and pass is in state in login and you can check it.
I hope this can help you