Angular 在嵌套 *ngFor 中将索引从父级传递到子级

Question

I want to display content with bunch of nested *ngFor loops and I want to keep track of the index of previous ngFor loop as a parent index. I couldn't find a way to pass the index of previous loop to the current one.

Here is what I try (doesn't work):

<div *ngFor="let parent of content; index as i" > 
    <span>{{parent.name}} index - {{i}}</span>
        <div *ngFor="let child of parent.childreen; i as parentIndex, index as i"  >
            <span>{{child.name}} index - {{i}} parentIndex - {{parentIndex}}   </span>
            <div *ngFor="let child of child.childreen; i as parentIndex, index as i">
                <span>{{child}} index - {{i}} parentIndex - parentIndex</span>
            </div>
        </div>
</div>

Is there any way that enable me to add previous index to parentIndex variable like above?

This is the example output that I want to achieve.

Parent 1 index - 0
Child 1.1 index - 0 parentIndex - 0
Child 1.1.1 index - 0 parentIndex - 0
Child 1.1.2 index - 1 parentIndex - 0
Child 1.1.3 index - 2 parentIndex - 0
Child 1.2 index - 1 parentIndex - 0
Child 1.2.1 index - 0 parentIndex - 1
Child 1.2.2 index - 1 parentIndex - 1
Child 1.2.3 index - 2 parentIndex - 1

Parent 2 index - 1
Child 2.1 index - 0 parentIndex - 1
Child 2.1.1 index - 0 parentIndex - 0
Child 2.1.2 index - 1 parentIndex - 0
Child 2.1.3 index - 2 parentIndex - 0
Child 2.2 index - 1 parentIndex - 1
Child 2.2.1 index - 0 parentIndex - 1
Child 2.2.2 index - 1 parentIndex - 1
Child 2.2.3 index - 2 parentIndex - 1

Here is the example of object that I used

  content: any[] = [
    {
      name: "Parent 1",
      childreen: [        
        {
        name: "Child 1.1",
        childreen: ["Child 1.1.1", "Child 1.1.2", "Child 1.1.3"]
      }, {
        name: "Child 1.2",
        childreen: ["Child 1.2.1", "Child 1.2.2", "Child 1.2.3"]
      }]
    }, {
      name: "Parent 2",
      childreen: [
        {
          name: "Child 2.1",
          childreen: ["Child 2.1.1", "Child 2.1.2", "Child 2.1.3"]
        }, {
          name: "Child 2.2",
          childreen: ["Child 2.2.1", "Child 2.2.2", "Child 2.2.3"]
        }
      ]
    }
  ]

Answer 1

Just use different local variable names for each *ngFor 's index.

<div *ngFor="let parent of content; index as i">
  <span>{{parent.name}} index - {{i}}</span>
  <div *ngFor="let child of parent.childreen; index as j">
    <span>{{child.name}} index - {{j}} parentIndex - {{i}}</span>
    <div *ngFor="let child of child.childreen; index as k">
      <span>{{child}} index - {{k}} parentIndex - {{i}} </span>
    </div>
  </div>
  <br>
</div>

Update

Working example: Stackblitz