and design 5.x版本中的tree组件拖拽功能

链接：https://4x.ant.design/components/tree-cn/#components-tree-demo-draggable

请问，这段代码什么情况下会被执行？

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 示例添加到头部，可以是随意位置
        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 = [];
  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 需要受控时设置
    // 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 示例添加到头部，可以是随意位置
        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 示例添加到头部，可以是随意位置
        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;

【以下回答由 GPT 生成】

我觉得代码中有一个小错误，当在loop(data, dropKey, (item) => {...});中调用loop函数时，参数名应该为dragKey而不是dropKey。下面是更正过的代码：

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 = [];
  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 loop = (data: DataNode[], prePos: React.Key[], siblingIndex?: number) => {
    const len = data.length;
    data.forEach((item, index) => {
      const pos = [...prePos, index];
      item.pos = pos.join('-');
      item.level = pos.length - 1;
      if (item.children && item.children.length > 0) {
        loop(item.children, pos);
      }
      if (siblingIndex !== undefined) {
        item.siblingPosition = siblingIndex;
      }
      if (index === 0) {
        item.isStart = true;
        item.isLeaf = index === len - 1;
        item.isEnd = index === 0 && item.isLeaf;
      } else if (index === len - 1) {
        item.isEnd = true;
        item.isLeaf = false;
      } else {
        item.isLeaf = false;
      }
    });
  };
  loop(tns, []);
  return tns;
};

const DraggableTree: React.FC<TreeProps> = () => {
  const [treeData, setTreeData] = useState(() => {
    const tns: DataNode[] = [];
    generateData(z, undefined, tns);
    return tns;
  });

  const loop = (data: DataNode[], callback: (item: DataNode, index: number, arr: DataNode[]) => void) => {
    data.forEach((item, index, arr) => {
      callback(item, index, arr);
      if (item.children && item.children.length > 0) {
        loop(item.children, callback);
      }
    });
  };

  const onDrop = (info: any) => {
    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]);

    if (
      ((info.node as any).props.children || []).length > 0 &&
      (info.node as any).props.expanded &&
      dropPosition === 1
    ) {
      loop(treeData, dragKey, (item) => {
        item.children = item.children || [];
        // where to insert 示例添加到头部，可以是随意位置
        item.children.unshift(dragObj);
        // in previous version, we use item.children.push(dragObj) to insert the
        // item to the tail of the children
      });
    }
  };

  return (
    <Tree
      draggable
      blockNode
      treeData={treeData}
      onDrop={onDrop}
    />
  );
};

export default DraggableTree;