如何在单击按钮时将绑定变量的值传递给模板中的方法

Question

I am learing how to make binding between the parent and the child using @Input, @Output and EventEmitter decorators. in the html section posted below

<h1 appItemDetails [item]="currentItem">{{currentItem}}</h1>

currentItem has value equal to "TV". and i pass this value to the binding variable item.

i added console.log in ngOnInit that prints the value of item to make sure that the binding from the parent to the child is working as suppose to be.

in

<button (click) = addNewItem(item.value)></button>

in this button tag i am trying to pass the value of the binding variable item to the method addNewItem() as a parameter. For the method addNewItem() it exists in the component and it should be invoked with the right parameter which is the value of the binding variable item

when i compile the App i revceive the error posted below. please let me know how to pass the value of the binding variable to a method on button clicked

error

TS2339: Property 'item' does not exist on type 'AppComponent'.

2 <button (click) = addNewItem(item.value)></button>
                               ~~~~

  src/app/app.component.ts:5:16
    5   templateUrl: './app.component.html',
                     ~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component AppComponent.

app.component.ts :

import { Component, Input, Output, EventEmitter } from '@angular/core';
@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'InputOutputBindings';
  currentItem = 'TV';

  @Output() newItemValue = new EventEmitter<string>();

  addNewItem(val : string) {
    this.newItemValue.emit(val);
    console.log("add new item");
  }
}

item-details.directive.ts :

import { Directive, Input, Output, EventEmitter } from '@angular/core';

@Directive({
  selector: '[appItemDetails]'
})
export class ItemDetailsDirective {

  @Input() item : string = "";

  constructor() { }
  ngOnInit() {
    console.log("ngOnInit->:" + this.item)
  }

}

app.coponent.html :

<h1 appItemDetails [item]="currentItem">{{currentItem}}</h1>
<button (click) = addNewItem(item.value)></button>

Answer 1

you can add exportAs like below:

@Directive({
  selector: '[appItemDetails]'
  exportAs: 'customdirective',
})
export class ItemDetailsDirective {
....
}

and in your html, you can add a reference to directive and get the binded value:

<h1 #test="customdirective" appItemDetails [item]="currentItem">{{currentItem}}</h1>
<button (click) = addNewItem(test.item)></button>