如何解决反应项目中显示的此错误 - 未捕获（承诺）TypeError：无法读取未定义的属性（读取'id'）

Question

import React ,{useEffect, useState}from 'react'

import Layout from '../components/Layout'

import axios from 'axios';

import TinderCard from 'react-tinder-card'

import MovieCard from '../components/MovieCard';

import { createClient } from '@supabase/supabase-js'

import { useAuth } from '../auth';


function Home() {

  const auth = useAuth();
  const supabaseUrl = process.env.REACT_APP_SUPABASE_URL
  const supabaseKey = process.env.REACT_APP_SUPABASE_KEY
  const supabase = createClient(supabaseUrl, supabaseKey)
  const [movies, setMovies] = useState([])
  const [message, setMessage] = useState("")
  
 const fecthMovies = async () => {
  const {data} = await axios.get("https://api.themoviedb.org/3/discover/movie",{
    params:{
      page:Math.random() * 501,
      api_key:"57e19e5c44a33653ce6bfc54743c9e2e"
    }
  })
 console.log(data);
const movie = await data;
setMovies(movie.results);
}
const addTowatchlist = async (movie) => {

const {data, error} = await supabase.from("watchlists").insert({movie_id : movie.id, user_id: auth.user.id})
if(error){
  console.log(error)
}
if(data){
  setMessage("Movie has been added to your watchlist")
}
}

 useEffect(() => {
  if(auth.user){
    fecthMovies()
  }
  
 
 },[auth])





return (
  <Layout>
    {message&&message}
    <h1>Welcome</h1>
    {!auth.user && <h2>Please sign up</h2>}

{movies.map(movie => {
 return <>
 <div className="movie-wrapper">
 <TinderCard
 onSwipe={direction => direction === "right"? addTowatchlist():null}
 key={movie.id}>
    <MovieCard movie={movie}/>
  
  </TinderCard>
 </div>
 
 </>
})}

  </Layout>
 )
 

}

export default Home

The above given is my Home.js. I don't know why it is showing undefined. I tried to change the 'movies' in 'movies.map' to 'Movies' and so but it didn't do that much. This error is happening when iam trying to add a item to the watchlist table i created in supabase database. And i need to add the movie 'id' iam getting from the item to watchlist table. when i tried this

const {data, error} = await supabase.from("watchlists").insert({movie_id : movie?.id, user_id: auth.user.id})

like adding? in 'movie.id' it works but i don't get the id because of the? . So how can i add the movie id to the list by fixing this error. I really appreciate the help. thanks in advance.

Answer 1

The?. operator is like the. chaining operator, except that instead of causing an error if a reference is nullish (null or undefined), the expression short-circuits with a return value of undefined. When used with function calls, it returns undefined if the given function does not exist.

so in the below code user_id: auth?.user?.id it will not be accessible until it is nullish and if it's null it will return undefined instead of crashing an application.

const {data, error} = await supabase.from("watchlists").insert({movie_id : movie?.id, user_id: auth?.user?.id})