I need to create a form that will display something based on the return value of an API. I'm working with the following code:
class App extends React.Component {
constructor(props) {
super(props);
this.state = {value: ''};
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChange(event) {
this.setState({value: event.target.value});
}
handleSubmit(event) {
alert('A name was submitted: ' + this.state.value); //error here
event.preventDefault();
}
render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
Name:
<input type="text" value={this.state.value} onChange={this.handleChange} /> // error here
</label>
<input type="submit" value="Submit" />
</form>
);
}
}
I'm getting the following error:
error TS2339: Property 'value' does not exist on type 'Readonly<{}>'.
I got this error in the two lines I commented on the code. This code isn't even mine, I got it from the react official site (https://reactjs.org/docs/forms.html), but it isn't working here.
Im using the create-react-app tool.
The Component is defined like so:
interface Component<P = {}, S = {}> extends ComponentLifecycle<P, S> { }
Meaning that the default type for the state (and props) is: {}.
If you want your component to have value in the state then you need to define it like this:
class App extends React.Component<{}, { value: string }> {
...
}
Or:
type MyProps = { ... };
type MyState = { value: string };
class App extends React.Component<MyProps, MyState> {
...
}
interface MyProps {
...
}
interface MyState {
value: string
}
class App extends React.Component<MyProps, MyState> {
...
}
// Or with hooks, something like
const App = ({}: MyProps) => {
const [value, setValue] = useState<string>('');
...
};
type's are fine too like in @nitzan-tomer's answer, as long as you're consistent.
If you don't want to pass interface state or props model you can try this
class App extends React.Component <any, any>