地图函数reactjs中的错误

Question

I am having an error with the map function. I dont know what might be the reason but it says this.state.rooms.map is not a function. I have fetched the data from api and pushed into an empty list . The list is successfully updated with the contents but could not apply map function on it.

Here's my code

import React from 'react';
import ReactDOM from 'react-dom';


export default class RoomList extends React.Component{
    constructor(props){
        super(props);
        this.state = { rooms: [] }
    }

    componentDidMount(){
        console.log('componentDidMount');
        this.loadRoomFromServer();
    }

    loadRoomFromServer(){
        $.ajax({
            url:'/api/v1/rental/',
            dataType:'json',
            success: (data) => {
                this.setState({rooms: data});
              },
              error: (xhr, status, err) => {
                console.error(url, status, err.toString());
              }
            });
    }

    render(){
        console.log('rooms',this.state.rooms);
        let listOfRoom = this.state.rooms.map((room)=>{
            return(
                    <Room key={room.id} name={room.listingName} price={room.price} number={room.room} />
                )
        });
        return(
                <div className="container-fluid">
                    <div className="row">
                            { listOfRoom }
                    </div>
                </div>
            )
    }
}

class Room extends React.Component{
    render(){
        return(
                <div className="col-md-4">
                    <h2>{this.props.name}</h2>
                    <p>{this.props.price}</p>
                    <p>{this.props.number}</p>
                </div>
            )
    }
}

what i get on the console is

room []

componentDidMount

room Object {amenities: "Kitchen, Cable", city: "city", email: "tushant@gmail.com", listingName: "tushant", ownerName: "tushant"…}

Uncaught TypeError: this.state.rooms.map is not a function

Answer 1

There is no map function for objects, only arrays.

Your second output of rooms shows the answer

room Object {amenities: "Kitchen, Cable", city: "city", email: 
"tushant@gmail.com", listingName: "tushant", ownerName: "tushant"…}

rooms is now an object and the map function is specific to arrays.

Answer 2

as @sfletche mentioned map function for arrays only. change your success callback to

success: (data) => {
    this.setState({rooms: data.objects});
 },
 error: (xhr, status, err) => {
    console.error(url, status, err.toString());
  }
});