[英]problem with infinite loop in function hook useEffect
I have a problem with an infinite loop on my hook, I'm passing the data of the local JSON breakfast. 我的钩子上存在无限循环问题,我正在传递本地JSON早餐的数据。 If you are iterating with map the data and I am taking it to paint a menu of buttons.
如果您要遍历地图数据,那么我将用它来绘制按钮菜单。 If I remove the data at the end of the function, and leave the empty array, it sends me the following error:
如果在函数末尾删除数据,并保留空数组,则会向我发送以下错误:
const BreakfastComponent = () => {
const breakfast = [
{
id: 0,
name: "Sandwich de jamón y queso",
price: '35',
img: "https://i.ibb.co/ynC9xHZ/sandjc.png",
},
{
id: 1,
name: "Jugo Natural",
price: '15',
img: "https://i.ibb.co/8mrd4MK/orangejuice.png",
},
{
id: 2,
name: "Café americano",
price: '20',
img: "https://i.ibb.co/nsj1GL0/americancoffe.png",
},
{
id: 3,
name: "Café con leche",
price: '28',
img: "https://i.ibb.co/GRPBm7j/coffeandmilk.png",
}
];
const [stateProduct, setStateProduct] = useState([ ]);
useEffect(() => {
setStateProduct(breakfast);
}, [breakfast]);
return (
<section className="databreakfast">
{stateProduct.map((element, item) =>
<ButtonsBComponent
key={item}
{...element}
/>
)}
</section>
)
};
export default BreakfastComponent;
React Hook useEffect has a missing dependency: 'breakfast'. React Hook useEffect缺少依赖项:“ breakfast”。 Either include it or remove the dependency array react-hooks/exhaustive-deps
包括它或删除依赖项数组react-hooks / exhaustive-deps
useEffect
's second argument is an array of state/hooks to be watched and when they change, to run the effect. useEffect
的第二个参数是要监视的状态/挂钩的数组,当状态/挂钩更改时,将运行效果。 Since your breakfast
is a const, I'm guessing you just want the original stateProduct
to be breakfast
. 由于您的
breakfast
是const,所以我猜您只想将原始stateProduct
breakfast
。 So instead of using []
as the default, use breakfast
. 因此,不要使用
[]
作为默认值,而应使用breakfast
。
const [stateProduct, setStateProduct] = useState(breakfast);
Also, probably a good idea to declare const breakfast ...
outside of your react functional component so it doesn't re-declare it on every re-render. 另外,在您的react功能组件之外声明
const breakfast ...
可能是一个好主意,这样它就不会在每次重新渲染时都重新声明它。
The problem is simple, you have breakfast
array as a dependency to useEffect
and in useEffect
you are setting the breakfast array itself. 问题很简单,您将
breakfast
数组作为对useEffect
的依赖useEffect
,在useEffect
您要设置Breakfast数组本身。 Now since the const breakfast array is declared inside the component, a new reference to it is generated everytime and since useEffect sets the array in state, it re-renders and on next re-render the comparison for breakfast
array fails since the reference has changed. 现在,由于在组件内部声明了const breakfast数组,因此每次都会生成对其的新引用,并且由于useEffect将数组设置为状态,因此它会重新渲染,并且在下一次重新呈现时,因为更改了引用,对
breakfast
数组的比较将失败。
The solution is simple, you don't need to have the const array in the component and also you don't need to use useEffect 解决方案很简单,您不需要在组件中包含const数组,也不需要使用useEffect
const breakfast = [
{
id: 0,
name: "Sandwich de jamón y queso",
price: '35',
img: "https://i.ibb.co/ynC9xHZ/sandjc.png",
},
{
id: 1,
name: "Jugo Natural",
price: '15',
img: "https://i.ibb.co/8mrd4MK/orangejuice.png",
},
{
id: 2,
name: "Café americano",
price: '20',
img: "https://i.ibb.co/nsj1GL0/americancoffe.png",
},
{
id: 3,
name: "Café con leche",
price: '28',
img: "https://i.ibb.co/GRPBm7j/coffeandmilk.png",
}
];
const BreakfastComponent = () => {
const [stateProduct, setStateProduct] = useState(breakfast);
return (
<section className="databreakfast">
{stateProduct.map((element, item) =>
<ButtonsBComponent
key={item}
{...element}
/>
)}
</section>
)
};
export default BreakfastComponent;
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