Angular2 - The Iterable Differ fails to detect changes

I am currently utilizing the Iterable Differs feature in Angular2 to monitor changes in my data. However, I am facing an issue where the differ.diff method always returns "null" and I am unsure of the reason behind this.

constructor(differs: IterableDiffers) {
    this.differ = differs.find([]).create(null);
}

@Input() data: any;

ngDoCheck() {
    var changes = this.differ.diff(this.data.datasets);
    if (changes && this.initialized) {
       //reload the view
    }

EDIT:

this.pingService.pingStream.subscribe(ping => {
                  this.ping = ping;
                  console.log(this.ping);
                  NTWDATA.datasets[0].data.shift();
                  NTWDATA.datasets[0].data.push(this.ping);

The PingService provides a number every 5 seconds by pinging the server. The shift/push operations are functioning correctly, and the data is being updated. However, it is not being detected. NTWDATA:

{
    labels: ["", "", "", "", "", "", ""],
    datasets: [
        {
            label: 'Server Response Time in ms',
            data: [65, 59, 80, 81, 56, 55, 40],
            fill: false,
            borderColor: '#FF0303'
        }
    ]
}

Answer №1

Depending on your needs, the IterableDiffers class will only detect:

  • Additions of elements to your array
  • Removals of elements from your array

However, it will not detect updates made within elements of your array.

You may find this question intriguing:

  • Detect changes in objects inside array in Angular2

Check out this plunkr for a practical example: https://plnkr.co/edit/wn6mTEcvrW2vh1ko5Ji5?p=preview.

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