Making an array render wait for an axios call - arrays

Question

My intention is to get the weather data for the selected country, passing selectedCountry.capital to the query, so it is displayed the weather from current country capital when the data of a country is displayed.
The problem is my code tries to render the weather data before the weather array is fetched, resulting in an error.
TypeError: Cannot read property 'temperature' of undefined
I get the array data
useEffect(() => {
if( selectedCountry.capital !== '' )
{
axios
.get(
`http://api.weatherstack.com/current?access_key=b51dfd70b0b2ccf136a0d7352876661c&query=${selectedCountry.capital}`
)
.then(res =>{
console.log(res.data)
console.log("capital" +selectedCountry.capital)
setWeather(res.data.current)
} )
}
}, [selectedCountry.capital])
render it
<div>
<h4>Weather</h4>
<h5>temperature: {weather.temperature} Celisues</h5>
<img src={weather.weather_icons[0]} alt='' />
<h5>
wind: {weather.wind_degree} mph direction {weather.wind_dir}
</h5>
</div>
i
If I don't render the array, I get the weather data just fine to the console. Also, If I add the array render code when the array is already there, the weather data gets displayed propperly.
What is the best way to make the array render wait for the array to be fetched from the axios call?
Full code
import React, { useState, useEffect } from 'react'
import axios from 'axios'
//setCountries is a function for setting the country's state
const App = () => {
const [countries, setCountries] = useState([])
//Filter
const [searchFilter, setSearchFilter] = useState('')
//Update state with button
const [selectedCountry, setSelectedCountry] = useState('')
const [weather, setWeather] = useState('')
const hook = () => {
console.log('effect')
axios
.get('https://restcountries.eu/rest/v2/all')
.then(response => {
console.log('promise fulfilled')
setCountries(response.data)
})
}
useEffect(hook,[])
/* by default the effect is always run after the component has been rendered. In our case, however, we only want to execute the effect along with the first render.
The second parameter of useEffect is used to specify how often the effect is run. If the second parameter is an empty array [], then the effect is only run along with the first render of the component. */
console.log('render', countries.length, 'countries')
console.log(countries)
/* weather */
useEffect(() => {
if( selectedCountry.capital !== '' )
{
axios
.get(
`http://api.weatherstack.com/current?access_key=b51dfd70b0b2ccf136a0d7352876661c&query=${selectedCountry.capital}`
)
.then(res =>{
console.log(res.data)
console.log("capital" +selectedCountry.capital)
setWeather(res.data.current)
} )
}
}, [selectedCountry.capital])
//When button es clicked the state is set, and the state variable is used
const renderCountryDetails = () => {
return (
selectedCountry && (
<p key={selectedCountry.alpha2Code}>
<p> Capital: {selectedCountry.capital}.</p>
<p> Population:{" "}
{selectedCountry.population}</p>
<p>
<img src={selectedCountry.flag} style={{ width: '200px'}}/>
</p>
<h3>Languages</h3>
<p> {selectedCountry.languages.map(language => <li key={language.name}>{language.name}</li>)}
<div>
<h4>Weather</h4>
<h5>temperature: {weather.temperature} Celisues</h5>
<img src={weather.weather_icons[0]} alt='' />
<h5>
wind: {weather.wind_degree} mph direction {weather.wind_dir}
</h5>
</div>
</p>
</p>
)
);
};
const filteredCountries =
searchFilter.length === 1
? countries
: countries.filter(
(country) => country.name.toLowerCase().indexOf(searchFilter.toLowerCase()) > -1
)
//showCountries returns either a message or else the contents of filteredcountries array
const showCountries = () => {
if (filteredCountries.length > 10) {
return 'Too many matches, keep on typing'
}
if (filteredCountries.length > 0
&& filteredCountries.length<10
&& filteredCountries.length>1 )
{
return (
<div>
{filteredCountries.map((country) => (
<p key={country.alpha2Code}>
{country.name}
{
//Update stste when button is clicked, passing country as a prop to the state
//onClick state is updated, causing the page to refresh and executing renderCountryDetails
//that uses the set state (the country) to render the info.
<button onClick={
() => setSelectedCountry(country)}>
show
</button>
}
</p>
))}
<div>{renderCountryDetails()}</div>
<div>
<p></p>
</div>
</div>
);
}
if (filteredCountries.length === 1) {
return filteredCountries.map((country) =>
<p key={country.alpha2Code}>
<p>Capital: {country.capital}.
<p> Population: {country.population} </p>
<h3>languages</h3>
{country.languages.map(language => <li key={language.name}>{language.name}</li>)}
<p><img src={country.flag} style={{ width: '200px'}}/>
</p>
</p>
</p>
)
}
}
const searchHandler = (e) => {
//setSelectedCountry state is set to empty
setSelectedCountry("");
setSearchFilter(e.target.value)
}
return (
<div>
<div>
<h1>Countries</h1>
</div>
<div>
Type to find countries:
<input onChange={searchHandler} />
<div>
{showCountries()}
</div>
</div>
</div>
);
}
export default App;

Answer 1

Simply use Optional chaining here:
<h5>temperature: {weather?.temperature||""} Celisues</h5>
In this case if the temperature is undefined it wont complain and would render an empty string instead.
"" can be replaced with any default value u need to show like 0 or something else in your case while your data is being fetched from API.
More on Optional chaining here:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining