useEffect not being called and not updating state when api is fetched

Question

I'm fetching data from a weather api using useEffect hook and declaring the dependency correctly as well. My state is still not being updated and I get errors in my render function because of that. I've pretty much tried everything from getting rid of the dependency array to declaring multiples in the dependency array. I don't know what's wrong with my function. The API's JSON response is in this format:

{
 location: {
 name: "Paris",
 region: "Ile-de-France",
 },
 current: {
  last_updated_epoch: 1564279222,
  last_updated: "2019-07-28 04:00",
  temp_c: 16,
  temp_f: 60.8,
  is_day: 0,
  condition: {
    text: "Clear",
    icon: "//cdn.apixu.com/weather/64x64/night/113.png",
    code: 1000
  },
  wind_mph: 6.9,
  wind_kph: 11.2
 }
}

and this is what my code looks like:

const Weather = ({ capital }) => {
  const [weather, setWeather] = useState(null);

  useEffect(() => {
    console.log("useEffect called");
    const getWeather = async () => {
      try {
        const res = await axios.get(
          `http://api.apixu.com/v1/current.json?key=53d601eb03d1412c9c004840192807&q=${capital}`
        );
        setWeather(res.data);
      } catch (e) {
        console.log(e);
      }
    };
    getWeather();
  }, [capital]);
  console.log(weather);

  return (
    <Card style={{ width: "18rem", marginTop: "25px" }}>
      <Card.Img variant="top" src={weather.current.condition.icon} />

      <Card.Header style={{ textAlign: "center", fontSize: "25px" }}>
        Weather in {capital}
      </Card.Header>
    </Card>
  )
}

I expect to get to be shown image of the icon but I get this error message in my render function:

TypeError: Cannot read property 'current' of null
Weather
src/components/Weather.js:26
  23 | 
  24 | return (
  25 |   <Card style={{ width: "18rem", marginTop: "25px" }}>
  26 |     <Card.Img variant="top" src={weather.current.condition.icon} />
     | ^  27 | 
  28 |     <Card.Header style={{ textAlign: "center", fontSize: "25px" }}>
  29 |       Weather in {capital}

and my console.log(weather) return null, the original state even though its being called after useEffect() and console.log(useEffect called) does not log at all which mean useEffect is not being called.

Answer 1

The error message gives it away, Cannot read property 'current' of null, the only place where current is called is in weather.current in the src of Card.Img, so we deduce that weather was null during the render.

The reason this happens is because the api call is asynchronus, it doesn't populate the state immediately, so the render happens first and tries to read .current from the initial weather state null.

Solution: in your render method, make sure not to read weather.current while weather is null.

You can for example use {weather && <Card>...</Card} to hide the whole card until the data is loaded and show a loading indicator, or you can use src={weather && weather.current.condition.icon} as a quick workaround.

const Weather = ({capital}) => {
  const [weather, setWeather] = useState(null);

  useEffect(() => {
    console.log("useEffect called");
    const getWeather = async () => {
      try {
        const res = await axios.get(
          `http://api.apixu.com/v1/current.json?key=53d601eb03d1412c9c004840192807&q=${capital}`,
        );
        setWeather(res.data);
      } catch (e) {
        console.log(e);
      }
    };
    getWeather();
  }, [capital]);
  console.log(weather);

  return (
    <Card style={{width: "18rem", marginTop: "25px"}}>
      <Card.Img variant="top" src={weather && weather.current.condition.icon} />

      <Card.Header style={{textAlign: "center", fontSize: "25px"}}>
        Weather in {capital}
      </Card.Header>
    </Card>
  );
};