Angular2 subscribing to changes to @Input in Child Component
<p>I have a parent and child component. Parent component has <code>index</code> and passes this through to the child component as an <code>@Input</code>. This <code>index</code> value constantly changes in the parent component, and inside my child component, I want to run a function everytime the Parent component changes <code>index</code>. This has a slide component that constantly changes it. How can I achieve this? I've tried with the below code (<code>this.index.subscribe(() =&gt;</code>), but I'm getting that it's not a function everytime I try and initialise the subscription.</p>

<p>EDIT: There is no related code in the <code>Child</code> template that could impact this, so it's not provided. <code>ngOnChange</code> doesn't seem to work as the change is happening in the directive as opposed to the <code>parent</code>'s template.</p>

<p>Child:</p>

<pre><code>import {Component, OnInit, ViewChild, Input} from '@angular/core';
import {Observable} from 'rxjs/Observable';

@Component({
    selector: "child",
    templateUrl: "components/child/child.html",
})

export class ChildComponent implements OnInit {
    @Input() index: string;
    currentIndex: any;

    constructor() {}

    ngOnInit() {}

    ngOnChanges(){}

    ngAfterViewInit() {
        console.log("index " + this.index);
        this.currentIndex = this.index.subscribe(() =&gt; {
             console.log("index " + this.index);
        })
    }

    ngOnDestroy() {
        this.currentIndex.unsubscribe();
    }

}
</code></pre>

<p>Parent:</p>

<pre><code>import {Component, ElementRef, OnInit, ViewChild} from '@angular/core';
import {Page} from "ui/page";
import {ChildComponent} from '/components/child/child.component'

@Component({
    selector: "parent",
    template: "&lt;child [index]="index"&gt;&lt;/child&gt;",
    directives: [ChildComponent]
})

export class ParentComponent implements OnInit {

    index: string = "0,1";

    constructor(private page: Page) {
    }



}
</code></pre>