useRef for element in loop in react [英] useRef for element in loop in react

问题描述

使用 React，我有一个以这种方式静态声明的 ref 列表:

Using React, i have a list of ref statically declared this way:

  let line1 = useRef(null);
  let line2 = useRef(null);
  let line3 = useRef(null);
  ...
  //IN MY RENDER PART
  <li ref={(el) => (line1 = el)}>line1</li>
  <li ref={(el) => (line2 = el)}>line1</li>
  <li ref={(el) => (line3 = el)}>line1</li>

然后将 refs 传递给动画函数，一切正常；现在事情发生了一些变化，我使用地图创建了列表项，但我不再能够正确引用该元素；我试过类似的东西:

the refs are then passed to an animation function and everything works correctly; now things changed a bit and i create the list item using map and im no longer able to ref the element correctly; i tried something like:

{menu.menu.map((D) => {
let newRef = createRef();
                    LiRefs.push(newRef);
                    return (
                      <li
                        key={D.id}
                        ref={(el) => (newRef = el)} >
                        {D.label}
                      </li>
                    );
                  })}

但是我传递给动画函数的数组是空的(我猜是因为该函数是在 useEffect 钩子内部调用的，而 LiRefs 还不是 useRef)我也知道我将创建的

的数量，所以我可以在开头声明它们，并使用类似

but the array i pass to the animation function is empty (i guess because the function is called inside useEffect hook and LiRefs is not yet a useRef) i also know the number of

i will create, so i can declare them at the beginning and the reference with something like

ref={(el) => (`line${i}` = el)}

这不起作用我可以尝试其他任何解决方案吗?

which is not working any other solution i could try?

推荐答案

Issue

当 menu 被映射时，这将不起作用，因为它会创建新的 react refs.

Issue

This won't work as each render when menu is mapped it creates new react refs.

使用 ref 保存生成的 ref 数组，并在映射时对其进行赋值.

Use a ref to hold an array of generated refs, and assign them when mapping.

const lineRefs = React.useRef([]);

lineRefs.current = menu.menu.map((_, i) => lineRefs.current[i] ?? createRef());

稍后在映射 UI 时，将存储在 lineRefs 中的 react ref 附加到索引 i

later when mapping UI, attach the react ref stored in lineRefs at index i

{menu.menu.map((D, i) => {
  return (
    <li
      key={D.id}
      ref={lineRefs.current[i]} // <-- attach stored ref
      {D.label}
    </li>
  );
})}

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