I'm trying to get values and insert them in the dropdown. But when I try to do that I get value as undefined instead of proper value. I want to get values from train array and populate dropdown with them. When I get station.name correct value is returned, but when i try to access train.number undefined value is returned.
import React, { Component } from 'react';
import StationService from '../services/StationService';
class CreateStationComponent extends Component {
constructor(props) {
super(props)
this.state = {
station: {
id: this.props.match.params.id,
city: '',
name: '',
trains: [
{
number: '',
numberOfCarriages: ''
}
]
}
}
this.changeCityHandles = this.changeCityHandles.bind(this);
this.changeNameHandles = this.changeNameHandles.bind(this);
this.saveStation = this.saveStation.bind(this);
}
componentDidMount() {
if (this.state.station.id === '_add') {
return;
} else {
StationService.getStationById(this.state.station.id).then((res) => {
let station = res.data;
this.setState({ name: station.name, city: station.city, number: station.trains.number })
});
}
// console.log(this.state.station.name + 'dfddddd');
}
changeCityHandles = (event) => {
this.setState({ number: this.state.station, trains: event.target.value });
}
changeNameHandles = (event) => {
this.setState({ name: event.target.value });
}
saveStation = (e) => {
e.preventDefault();
let station = { city: this.state.city, name: this.state.name, number: this.state.train.number, numberOfCarriages: this.state.train.numberOfCarriages }
if (this.state.station.id === '_add') {
StationService.createStation(station).then(res => {
this.props.history.push('/stations');
});
} else {
StationService.updateStation(station, this.state.station.id).then(res => {
this.props.history.push('/stations');
});
}
}
cancel() {
this.props.history.push('/stations');
}
getTitle() {
if (this.state.id === '_add') {
return <h3 className="text-center">Dodaj stację</h3>
} else {
return <h3 className="text-center">Modyfikuj stację</h3>
}
}
render() {
return (
<div>
<div className="container">
<div className="row">
<div className="card-body">
<form>
<div className="form-group">
<input name="name" className="form-control" value={this.state.name} onChange={this.changeNameHandles} />
</div>
<select>
{this.state.station.trains.map(train => <option key={train.id} value={train.number}>{train.number}</option>)}
</select>
</form>
</div>
</div>
</div>
</div>
);
}
}
Try this:-
{this.state.station && this.state.station.trains.length &&
&& this.state.station.trains.map((train , i) => {
return (
<React.Fragment>
{ train && train?.number &&
<option key={train?.id} value={train?.number}>{train?.number}</option>
}
</React.Fragment>
);
})
}
It's trains[0].number
not trains.number
, because the object you are trying to access is nested in an array.
StationService.getStationById(this.state.station.id).then((res) => {
let station = res.data;
this.setState({ name: station.name, city: station.city, number: station.trains.number })
});
This code tries to set state variables of name, city and number. Instead try doing this
StationService.getStationById(this.state.station.id).then((res) => {
let station = res.data;
this.setState({ station: {
...state.station,
name: station.name,
city: station.city,
trains: station.trains }
})
});
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