and design 5.x版本中的tree组件拖拽功能

Question

谁帮我解释一下这段代码什么意思?

if (
      ((info.node as any).props.children || []).length > 0 && // Has children
      (info.node as any).props.expanded && // Is expanded
      dropPosition === 1 // On the bottom gap
    ) {
      loop(data, dropKey, (item) => {
        item.children = item.children || [];
        // where to insert. New item was inserted to the start of the array in this example, but can be anywhere
        item.children.unshift(dragObj);
        // in previous version, we use item.children.push(dragObj) to insert the
        // item to the tail of the children
      });
    }

完整代码:

import { Tree } from 'antd';
import type { DataNode, TreeProps } from 'antd/es/tree';
import React, { useState } from 'react';

const x = 3;
const y = 2;
const z = 1;
const defaultData: DataNode[] = [];

const generateData = (_level: number, _preKey?: React.Key, _tns?: DataNode[]) => {
  const preKey = _preKey || '0';
  const tns = _tns || defaultData;

  const children: React.Key[] = [];
  for (let i = 0; i < x; i++) {
    const key = `${preKey}-${i}`;
    tns.push({ title: key, key });
    if (i < y) {
      children.push(key);
    }
  }
  if (_level < 0) {
    return tns;
  }
  const level = _level - 1;
  children.forEach((key, index) => {
    tns[index].children = [];
    return generateData(level, key, tns[index].children);
  });
};
generateData(z);

const App: React.FC = () => {
  const [gData, setGData] = useState(defaultData);
  const [expandedKeys] = useState(['0-0', '0-0-0', '0-0-0-0']);

  const onDragEnter: TreeProps['onDragEnter'] = (info) => {
    console.log(info);
    // expandedKeys, set it when controlled is needed
    // setExpandedKeys(info.expandedKeys)
  };

  const onDrop: TreeProps['onDrop'] = (info) => {
    console.log(info);
    const dropKey = info.node.key;
    const dragKey = info.dragNode.key;
    const dropPos = info.node.pos.split('-');
    const dropPosition = info.dropPosition - Number(dropPos[dropPos.length - 1]);

    const loop = (
      data: DataNode[],
      key: React.Key,
      callback: (node: DataNode, i: number, data: DataNode[]) => void,
    ) => {
      for (let i = 0; i < data.length; i++) {
        if (data[i].key === key) {
          return callback(data[i], i, data);
        }
        if (data[i].children) {
          loop(data[i].children!, key, callback);
        }
      }
    };
    const data = [...gData];

    // Find dragObject
    let dragObj: DataNode;
    loop(data, dragKey, (item, index, arr) => {
      arr.splice(index, 1);
      dragObj = item;
    });

    if (!info.dropToGap) {
      // Drop on the content
      loop(data, dropKey, (item) => {
        item.children = item.children || [];
        // where to insert. New item was inserted to the start of the array in this example, but can be anywhere
        item.children.unshift(dragObj);
      });
    } else if (
      ((info.node as any).props.children || []).length > 0 && // Has children
      (info.node as any).props.expanded && // Is expanded
      dropPosition === 1 // On the bottom gap
    ) {
      loop(data, dropKey, (item) => {
        item.children = item.children || [];
        // where to insert. New item was inserted to the start of the array in this example, but can be anywhere
        item.children.unshift(dragObj);
        // in previous version, we use item.children.push(dragObj) to insert the
        // item to the tail of the children
      });
    } else {
      let ar: DataNode[] = [];
      let i: number;
      loop(data, dropKey, (_item, index, arr) => {
        ar = arr;
        i = index;
      });
      if (dropPosition === -1) {
        ar.splice(i!, 0, dragObj!);
      } else {
        ar.splice(i! + 1, 0, dragObj!);
      }
    }
    setGData(data);
  };

  return (
    <Tree
      className="draggable-tree"
      defaultExpandedKeys={expandedKeys}
      draggable
      blockNode
      onDragEnter={onDragEnter}
      onDrop={onDrop}
      treeData={gData}
    />
  );
};

export default App;

Answer 1

if (
  // 如果节点有子节点
  ((info.node as any).props.children || []).length > 0 &&
  // 并且节点是展开状态
  (info.node as any).props.expanded &&
  // 并且拖放位置在底部间隙
  dropPosition === 1
) {
  // 遍历数据，找到要插入的位置
  loop(data, dropKey, (item) => {
    // 如果节点没有子节点，则初始化子节点数组
    item.children = item.children || [];
    // 将拖拽的对象插入到子节点数组的开头
    item.children.unshift(dragObj);
    // 在之前的版本中，我们使用item.children.push(dragObj)将对象插入到子节点的末尾
  });
}

其实你完整的代码有注释啊，英文注释 。
info.node as any 这个是将info.node强制断言为any类型 。
在TypeScript中，当编译器无法确定一个值的具体类型时，会使用类型推断来推断出最合适的类型