score:6

Accepted answer

In your

canvas ... add a #yourId

(example : canvas *ngFor="let chart of charts; let i = index" id="canvas{{i}} #yourId")

Then you can use @ViewChildren('yourId') myCharts: any; (you can't use myCharts in ngOnInit, only in ngAfterViewInit and after) which will give you your array of charts.

I won't provide much more detail but you can use what's inside your myCharts (use a console.log(myCharts) to see in detail what's in there), you can use this to change data and so on.

Hope this helps.

score:3

Here is one of the possible implementations of the previously proposed solution. I created an array called "charts", which will contain as many elements as charts I want to create. Each element of this array has an identifier and the key where we will place the chart later (AfterViewInit).

HTML: 

<div>
  <canvas *ngFor="let chart of charts; let i = index" id="mychart{{i}}" #mycharts>{{chart.chart}}</canvas>
</div>

.TS:

 import {Component, OnInit, Input, AfterViewInit, ViewChildren} from '@angular/core';
 import { Chart } from 'chart.js';

 // ...

 @ViewChildren('mycharts') allMyCanvas: any;  // Observe #mycharts elements
 charts: any;    // Array to store all my charts

 constructor() {
   this.charts = [
    {
      "id": "1",   // Just an identifier
      "chart": []            // The chart itself is going to be saved here
    },
    {
      "id": "2",
      "chart": []
    },
    {
      "id": "3",
      "chart": []
    }
  ]
 }

 ngAfterViewInit() {
   let canvasCharts = this.allMyCanvas._results;  // Get array with all canvas
   canvasCharts.map((myCanvas, i) => {   // For each canvas, save the chart on the charts array 
      this.charts[i].chart = new Chart(myCanvas.nativeElement.getContext('2d'), {
        // ...
      }
   })
 }

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