Make sure you're calling super() as the first thing in your constructor.
You should set this for setAuthorState method
class ManageAuthorPage extends Component {
state = {
author: { id: '', firstName: '', lastName: '' }
};
constructor(props) {
super(props);
this.handleAuthorChange = this.handleAuthorChange.bind(this);
}
handleAuthorChange(event) {
let {name: fieldName, value} = event.target;
this.setState({
[fieldName]: value
});
};
render() {
return (
<AuthorForm
author={this.state.author}
onChange={this.handleAuthorChange}
/>
);
}
}
Another alternative based on arrow function:
class ManageAuthorPage extends Component {
state = {
author: { id: '', firstName: '', lastName: '' }
};
handleAuthorChange = (event) => {
const {name: fieldName, value} = event.target;
this.setState({
[fieldName]: value
});
};
render() {
return (
<AuthorForm
author={this.state.author}
onChange={this.handleAuthorChange}
/>
);
}
}