How do I programmatically select Material Tree nodes with SelectionModel?

Question

I have a tree with checkboxes (let\'s use Material\'s example here). I\'d like the fruit nodes to begin checked. How do I check those nodes?

I see that SelectionMo

Answer 1

To pre-select the fruits node implement the following in an ngAfterViewInit for the TreeChecklistExample class in the attached stackblitz example.

• This will loop through the dataNodes in the treeControl
• If item == 'Fruits' select node and expand

• Also if item == 'Groceries' expand node as it is the parent of Fruits.

  ngAfterViewInit() {
      for (let i = 0; i < this.treeControl.dataNodes.length; i++) {
        if (this.treeControl.dataNodes[i].item == 'Fruits') {
          this.todoItemSelectionToggle(this.treeControl.dataNodes[i]);
          this.treeControl.expand(this.treeControl.dataNodes[i])
        }
        if (this.treeControl.dataNodes[i].item == 'Groceries') {
          this.treeControl.expand(this.treeControl.dataNodes[i])
        }
      }
    }
  

Stackblitz

https://stackblitz.com/edit/angular-j2nf2r?embed=1&file=app/tree-checklist-example.html

---