We have one way to update (or re-render) a component.
It's React.useState.
When we want to render our component with data we've useEffected from the internet, we need to need a useState updater function to call.
This is a common pairing of functions where server data is used to update a component:
let [componentData, setComponentData] = React.useState(null);
React.useEffect(() => {
fetchData().then(serverData => setComponentData(serverData));
})
In our Pokemon app, that looks like this:
let [index, setIndex] = React.useState(1);
let [pokemon, setPokemon] = React.useState(null);
React.useEffect(() => {
fetchPokemon(index).then(json => setPokemon(json));
});
Our useEffect connects us to the outside world — fetching data with JavaScript.
The callback we give to fetchPokemon calls our useState updater function when data is ready — updating our component.
Give it a try!
Assignment Sandbox:
Assignment:
- Update the
let pokemonassignment to get it's value fromReact.useState(null) - Using destructuring assignment, take the second element of
React.useState's return (our updater function) andsetPokemon - Replace
console.log(json)with a call tosetPokemon(json)
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Top comments (2)
How do you feel about putting
{index, pokemon}into a reducer, so you only have one "state" object?Do you think it is too much here because they always update independently?
great question!
You could go either way, depending on your comfort with reducers.
I think the end result would impact my preference.
For example, I don't like having two pieces of state in a reducer that control the same outcome —
indexandpokemon.I think it'd depend a lot of the final component whether I kept
indexorpokemonin the reducer.I'll try to flesh that out a little more in the later lessons.
Thanks for asking!