Contents Bidirectional data flow between components(@Input & @Output) Bidirectional data flow between components Sometimes, not work very well. ABANDON @Input value and @Output valueChange cannot detect value change when child component valueChange emit a value, especially, Multiple inheritance. next, try to use @ViewChild or @ViewChildren Bidirectional data flow between parent component and child component. It uses @Input and @Output decorates the variables. The more Input and Output details are at official angular guide