You have `(click)=”tooltip.toggleTooltip()`, but the closest bit in the directive is `private _toggleTooltip()`. Is there some sort of magic that links those up? Is it made public and the underscore removed or do we have access to all private members when we `@Input() tooltip;`?
Which version of Angular2 are you working with? I cannot get any extra capabilities beyond what is explicitly stated in the official example: https://angular.io/docs/ts/latest/guide/attribute-directives.html