React Hook useEffect has missing dependencies question

Question

i have this problem:

 Line 25:7:  React Hook useEffect has missing dependencies: 'getSingleProductData', 'isProductOnSale', and 'productData'. Either include them or remove the dependency array  react-hooks/exhaustive-deps

this is the code:

    type SingleProductParams = {
    s_id:string;
}

type SingleProductProps = RouteComponentProps<SingleProductParams>

const SingleProduct: React.FC<SingleProductProps> = (props) => {
    let [productData, setProductData] = useState<Partial<IProdItems>>({});
    let [isProductOnSale, setIsProductOnSale] = useState<Sale['onSale']>();

    useEffect( () => { 
        setIsProductOnSale(productData.sale?.onSale);
        getSingleProductData();
        console.log(productData);
        console.log(isProductOnSale);
        console.log(props.match.params.s_id);
    },[props]) 
    
    const getSingleProductData = async() => { 
        let url = URL_API + "/products/single/" + props.match.params.s_id;
        let data = await doApiGet(url);
        console.log(data);
        setProductData(data);
    }

how can I fix it? i tried every way from google, that's just doesn't work. but the page all work, i get the data and it's all fine. should i disable the error? I must mention that the console logs inside the useEffect is undefined but the data shown in the site!

Giovanni Esposito · Accepted Answer · 2021-08-04 13:12:29Z

2

The warning means that you need to add getSingleProductData, isProductOnSale and productData to useEffect's deps list in this way:

useEffect( () => { 
    setIsProductOnSale(productData.sale?.onSale);
    getSingleProductData();
    console.log(productData);
    console.log(isProductOnSale);
    console.log(props.match.params.s_id);
},[props, getSingleProductData, isProductOnSale, productData]) //<-- here add them

And warning disappears.

EDIT

By adding these dependencies you could fall into the loop problem (useEffect has a dependency that will be updated in useEffect itself).

In this case you could initialize multiple useEffects, everyone with needed dependencies:

useEffect(() => {  //<-- this useEffect to set productData (it runs just one time at component loading)
    getSingleProductData(); 
},[]) 

useEffect(() => { //<-- this useEffect to set isProductOnSale every time productData changes 
   setIsProductOnSale(productData.sale?.onSale);
}, [productData])

useEffect(() => { //<-- this useEffect print stuff
    console.log(productData);
    console.log(isProductOnSale);
    console.log(props.match.params.s_id);
}, [productData, isProductOnSale, props])

edited Aug 4, 2021 at 13:12

answered Aug 4, 2021 at 12:40

Giovanni Esposito

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5 Comments

JeroenE Over a year ago

diappears = disappears. (can't added as it needs atleast 6 charachters). But this is the solution, was going to answer the same. :-)

Aluf Over a year ago

yea that doesn't work, it just render the data every time. and it doesn't let me add a function to the deps list.

Giovanni Esposito Over a year ago

@Aluf dependencies problem will be solved like this. You could have another problem: if some function in useEffect modifies one or more elements in deps list then you will have a loop. Is this the case?

Aluf Over a year ago

yea that's the case, it keeps render the data with a loop. @GiovanniEsposito

Aluf Over a year ago

hey that half worked, when i try your edit of code it keep on giving me the error about the function: Line 22:7: React Hook useEffect has a missing dependency: 'getSingleProductData' and when I pass it to one of the deps it rendering loop the function. got any ideas? :( @GiovanniEsposito

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