Almost anything can be represented in a tree structure. Examples include directories, organization hierarchies, biological classifications, countries, etc. The `Tree` component is a way of representing the hierarchical relationship between these things. You can also expand, collapse, and select a treeNode within a `Tree`.
| checkable | Add a Checkbox before the treeNodes | boolean | false | |
| checkedKeys | (Controlled) Specifies the keys of the checked treeNodes (PS: When this specifies the key of a treeNode which is also a parent treeNode, all the children treeNodes of will be checked; and vice versa, when it specifies the key of a treeNode which is a child treeNode, its parent treeNode will also be checked. When `checkable` and `checkStrictly` is true, its object has `checked` and `halfChecked` property. Regardless of whether the child or parent treeNode is checked, they won't impact each other | string\[] \| {checked: string\[], halfChecked: string\[]} | \[] | |
| draggable | Specifies whether this Tree is draggable (IE > 8) | boolean | false | |
| expandedKeys | (Controlled) Specifies the keys of the expanded treeNodes | string\[] | \[] | |
| filterTreeNode | Defines a function to filter (highlight) treeNodes. When the function returns `true`, the corresponding treeNode will be highlighted | function(node) | - | |
| showIcon | Shows the icon before a TreeNode's title. There is no default style; you must set a custom style for it if set to true | boolean | false | |
| showLine | Shows a connecting line | boolean \| {showLeafIcon: boolean} | false | |
| treeData | The treeNodes data Array, if set it then you need not to construct children TreeNode. (key should be unique across the whole array) | array<{ key, title, children, \[disabled, selectable] }> | - | |
| virtual | Disable virtual scroll when set to false | boolean | true | 4.1.0 |
| isLeaf | Determines if this is a leaf node(effective when `loadData` is specified). `false` will force trade TreeNode as a parent node | boolean | - | |
| key | Used with (default)ExpandedKeys / (default)CheckedKeys / (default)SelectedKeys. P.S.: It must be unique in all of treeNodes of the tree | string | (internal calculated position of treeNode) | |
Before `3.4.0`: The number of treeNodes can be very large, but when `checkable=true`, it will increase the compute time. So, we cache some calculations (e.g. `this.treeNodesStates`) to avoid double computing. But, this brings some restrictions. **When you load treeNodes asynchronously, you should render tree like this**:
### Why defaultExpandedAll not working on ajax data?
`default` prefix prop only works when inited. So `defaultExpandedAll` has already executed when ajax load data. You can control `expandedKeys` or render Tree when data loaded to realize expanded all.
### What does `disabled` node work logic in the tree?
Tree change its data by conduction. Includes checked or auto expanded, it will conduction state to parent / children node until current node is `disabled`. So if a controlled node is `disabled`, it will only modify self state and not affect other nodes. For example, a parent node contains 3 child nodes and one of them is `disabled`. When check the parent node, it will only check rest 2 child nodes. As the same, when check these 2 child node, parent will be checked whatever checked state the `disabled` one is.
This conduction logic prevent that modify `disabled` parent checked state by check children node and user can not modify directly with click parent which makes the interactive conflict. If you want to modify this conduction logic, you can customize it with `checkStrictly` prop.
