antd vue tree settings are selected by default

When using the Ant Design Vue component library in a Vue project, it is often necessary to use the Tree (tree control) component to display hierarchical structure data. When users use Tree, they may need to select certain nodes by default. This article will introduce how to use the Tree component of Ant Design Vue to achieve default selection.

1. Set the default selection in the data source

Suppose now we have the following tree structure data:

treeData: [
  {
    title: 'Node1',
    key: 'node1',
    children: [
      {
        title: 'Node1.1',
        key: 'node1-1',
        children: [
          {
            title: 'Node1.1.1',
            key: 'node1-1-1',
            isLeaf: true
          },
          {
            title: 'Node1.1.2',
            key: 'node1-1-2',
            isLeaf: true
          }
        ]
      },
      {
        title: 'Node1.2',
        key: 'node1-2',
        isLeaf: true
      }
    ]
  },
  {
    title: 'Node2',
    key: 'node2',
    isLeaf: true
  }
]

We want the default selectionNode1.1.2Node. Then we can add a selected attribute to the data object of the node and set it to true:

treeData: [
  {
    title: 'Node1',
    key: 'node1',
    children: [
      {
        title: 'Node1.1',
        key: 'node1-1',
        children: [
          {
            title: 'Node1.1.1',
            key: 'node1-1-1',
            isLeaf: true
          },
          {
            title: 'Node1.1.2',
            key: 'node1-1-2',
            isLeaf: true,
            selected: true // 将该节点设置为默认选中
          }
        ]
      },
      {
        title: 'Node1.2',
        key: 'node1-2',
        isLeaf: true
      }
    ]
  },
  {
    title: 'Node2',
    key: 'node2',
    isLeaf: true
  }
]

Next, set the The selected attribute of the node is mapped to the selectedKeys attribute of the component to complete the default selection:

<template>
  <a-tree :tree-data="treeData" :selected-keys="selectedKeys"></a-tree>
</template>

<script>
export default {
  data() {
    return {
      treeData: [
        {
          title: 'Node1',
          key: 'node1',
          children: [
            {
              title: 'Node1.1',
              key: 'node1-1',
              children: [
                {
                  title: 'Node1.1.1',
                  key: 'node1-1-1',
                  isLeaf: true
                },
                {
                  title: 'Node1.1.2',
                  key: 'node1-1-2',
                  isLeaf: true,
                  selected: true // 将该节点设置为默认选中
                }
              ]
            },
            {
              title: 'Node1.2',
              key: 'node1-2',
              isLeaf: true
            }
          ]
        },
        {
          title: 'Node2',
          key: 'node2',
          isLeaf: true
        }
      ],
      selectedKeys: []
    };
  },

  mounted() {
    this.selectedKeys = this.treeData.flatMap(node => {
      if (node.selected) {
        return node.key;
      } else if (node.children) {
        return node.children.flatMap(child => {
          if (child.selected) {
            return child.key;
          } else {
            return [];
          }
        });
      } else {
        return [];
      }
    });
  }
};
</script>

In this example, we use ES6’s Array .prototype.flatMap() method to map the key values ​​of all selected nodes to the selectedKeys array. flatMap()The method can flatten nested arrays into a one-dimensional array.

2. Use defaultExpandedKeysSet the default expanded node

In addition to the selectedKeys attribute, Ant Design Vue’s Tree component also has a defaultExpandedKeysAttribute, used to set the default expanded nodes. This property receives an array of strings indicating which nodes need to be expanded by default.

If in the above tree structure data, we hope to expand the Node1 node and its sub-nodes by default. Then we can set defaultExpandedKeys to:

defaultExpandedKeys: ['node1']

The complete code is as follows:

<template>
  <a-tree :tree-data="treeData" :selected-keys="selectedKeys" :default-expanded-keys="defaultExpandedKeys"></a-tree>
</template>

<script>
export default {
  data() {
    return {
      treeData: [
        {
          title: 'Node1',
          key: 'node1',
          children: [
            {
              title: 'Node1.1',
              key: 'node1-1',
              children: [
                {
                  title: 'Node1.1.1',
                  key: 'node1-1-1',
                  isLeaf: true
                },
                {
                  title: 'Node1.1.2',
                  key: 'node1-1-2',
                  isLeaf: true,
                  selected: true // 将该节点设置为默认选中
                }
              ]
            },
            {
              title: 'Node1.2',
              key: 'node1-2',
              isLeaf: true
            }
          ]
        },
        {
          title: 'Node2',
          key: 'node2',
          isLeaf: true
        }
      ],
      selectedKeys: [],
      defaultExpandedKeys: ['node1'] // 将node1设置为默认展开节点
    };
  },

  mounted() {
    this.selectedKeys = this.treeData.flatMap(node => {
      if (node.selected) {
        return node.key;
      } else if (node.children) {
        return node.children.flatMap(child => {
          if (child.selected) {
            return child.key;
          } else {
            return [];
          }
        });
      } else {
        return [];
      }
    });
  }
};
</script>

Summary:

Set the Tree component of Ant Design Vue to be selected by default This can be achieved by marking the selected node in the data source and mapping it to the selectedKeys attribute in the component. At the same time, use the defaultExpandedKeys attribute to set the default expanded nodes.

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