ExpressionChangedAfterItHasBeenCheckedError

onInit.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-child',
  template: `<span>{{count}}</span>`,
})
export class ChildComponent implements OnInit {

  count = 0;

  constructor() { }

  increaseCount() {
    this.count += 1;
  }

  ngOnInit() {
    this.increaseCount()
  }
}