Angular2 single ngFor for multiple arrays

Question

Is it possible to use multiple array's for ngFor in Angular?

   *ngFor="let device of element.devices && element.zones.devices"// something like this

export interface Element {
    id: string;
    name: string;   
    zones: Zone[];
    devices: Device[];
}

export class Zone {
    id: string;
    name: string;
    devices: Device[];
}

export class Device {
    id: string;
    name: string;
}

I'll be having access to Element object, from that I need to display all the devices and devices inside zones.

Answer 1

使用concat连接两个数组，然后ngFor使用ngFor

*ngFor = "let device of arr1.concat(arr2.devices)"

Answer 2

You can concatenate two arrays as below

this.elements= arr1.concat(arr2);

In addition, to avoid the undefined error you should be using ? type safe operator as below

<div *ngFor="let device of elements?.devices">
    <span> {{device?.name}} </span>
</div>