angular material - How to update nested mat-tree dynamically

Angular material - How to update nested mat-tree dynamically

To dynamically update a nested mat-tree in Angular Material, you can manipulate the underlying data source and then trigger a refresh of the tree. Here's a step-by-step guide:

Assuming you have a nested data structure like this:

interface TreeNode { name: string; children?: TreeNode[]; }

  1. Create a data source: Use a MatTreeNestedDataSource to manage the data for the tree:

    import { NestedTreeControl } from '@angular/cdk/tree'; import { MatTreeNestedDataSource } from '@angular/material/tree'; // ... treeControl = new NestedTreeControl<TreeNode>(node => node.children); dataSource = new MatTreeNestedDataSource<TreeNode>(); constructor() { this.dataSource.data = /* initial data */; // Optional: Expand the entire tree by default this.treeControl.dataNodes.forEach(node => this.treeControl.expand(node)); }

  2. Update the Data Source: Modify your data source (this.dataSource.data) to include the changes you want. You can add, remove, or update nodes in the data source dynamically.

  3. Trigger a Refresh: After updating the data source, call the dataNodes setter on the treeControl to trigger a refresh of the tree:

    updateTree(): void { // Update this.dataSource.data with your changes // Trigger a refresh this.treeControl.dataNodes = this.treeControl.dataNodes; }

  4. Update the Template: Ensure your template is bound to the treeControl and dataSource:

    <mat-tree [dataSource]="dataSource" [treeControl]="treeControl"> <!-- Your tree template here --> <mat-tree-node *matTreeNodeDef="let node" matTreeNodePadding> {{ node.name }} <button mat-icon-button disabled></button> </mat-tree-node> <!-- Recursively handle nested nodes --> <mat-nested-tree-node *matTreeNodeDef="let node; when: hasChild"> <div matTreeNodePadding> <button mat-icon-button matTreeNodeToggle> <mat-icon>{{ treeControl.isExpanded(node) ? 'expand_more' : 'chevron_right' }}</mat-icon> </button> {{ node.name }} </div> <div [class.example-tree-invisible]="!treeControl.isExpanded(node)"> <ng-container matTreeNodeOutlet></ng-container> </div> </mat-nested-tree-node> </mat-tree>

  5. Handle Node Expansion/Collapse: Make sure you handle the matTreeNodeToggle button click to expand/collapse nodes:

    <button mat-icon-button matTreeNodeToggle> <mat-icon>{{ treeControl.isExpanded(node) ? 'expand_more' : 'chevron_right' }}</mat-icon> </button>

    This ensures that the tree updates visually when nodes are expanded or collapsed.

By following these steps, you can dynamically update the nested mat-tree in Angular Material. Adjust the code to fit your specific use case and requirements.

Examples

  1. Angular Material mat-tree dynamic data update:

    • Description: Updating data dynamically in an Angular Material mat-tree.
    // Update the data source when your nested tree data changes this.dataSource.data = this.getUpdatedTreeData();

  2. MatTreeDataSource not updating when nested data changes:

    • Description: Resolving issues when the MatTreeDataSource does not automatically update when nested tree data changes.
    // Manually trigger the data source update this.dataSource.data = [...this.dataSource.data];

  3. Angular Material tree refresh after data change:

    • Description: Forcing a refresh of the Angular Material tree when nested data is updated.
    // Use a temporary variable to force a refresh const data = this.dataSource.data; this.dataSource.data = null; this.dataSource.data = data;

  4. MatTree nested nodes not updating dynamically:

    • Description: Addressing issues when nested nodes in a MatTree do not update dynamically.
    // Create a new reference for the nested node array to trigger change detection node.children = [...node.children];

  5. How to refresh Angular Material tree after adding new node:

    • Description: Ensuring the Angular Material tree is refreshed after dynamically adding a new node.
    // Add a new node to the parent's children array and then refresh the tree parent.children.push(newNode); this.dataSource.data = [...this.dataSource.data];

  6. MatTreeDataSource update when nested node properties change:

    • Description: Handling updates when properties of nested nodes change in an Angular Material tree.
    // Manually update the specific node in the data array const index = this.dataSource.data.indexOf(node); this.dataSource.data[index] = updatedNode; this.dataSource.data = [...this.dataSource.data];

  7. Angular Material tree dynamic expansion not working:

    • Description: Fixing issues when dynamically expanded nodes do not work as expected in an Angular Material tree.
    // Ensure that the nested nodes are set to expanded when dynamically updating node.expanded = true; this.dataSource.data = [...this.dataSource.data];

  8. MatTree flatMap data update not reflecting changes:

    • Description: Addressing issues when using flatMap in MatTree and changes are not reflected dynamically.
    // Use spread operator to create a new array reference const updatedData = [...this.dataSource.data]; this.dataSource.data = updatedData.flatMap(...); // Update your flatMap logic

  9. Angular Material tree nested node deletion not updating:

    • Description: Handling issues when deleting a nested node does not update the Angular Material tree.
    // Remove the node from the parent's children array and then update the tree parent.children = parent.children.filter(child => child !== deletedNode); this.dataSource.data = [...this.dataSource.data];

  10. MatTreeDataSource not updating on node move:

    • Description: Addressing problems when the MatTreeDataSource does not update after moving a node within the tree.
    // Manually update the data array after moving a node this.dataSource.data = [...this.dataSource.data];

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