Ionic open a Popover from another component within a page

Question

I know that this question already exists here: Ionic open Popover from another component but I don't get the solution.

I have a page which includes a component for the toolbar which has an button. This button should trigger a function within the page. When I trigger the function from inside the page it works. I can also see that onInit the popoverController is filled, but later when the function is executed it's undefined.

ERROR TypeError: Cannot read property 'create' of undefined
at HeaderComponent.push.6176.LocationSelectionPage.openAddLocation (location-selection.page.ts:92)
at HeaderComponent_ion_buttons_7_Template_ion_buttons_click_0_listener (template.html:14)
at executeListenerWithErrorHandling (core.js:15285)
at wrapListenerIn_markDirtyAndPreventDefault (core.js:15323)
at HTMLElement.<anonymous> (platform-browser.js:560)
at ZoneDelegate.invokeTask (zone.js:406)
at Object.onInvokeTask (core.js:28664)
at ZoneDelegate.invokeTask (zone.js:405)
at Zone.runTask (zone.js:178)
at ZoneTask.invokeTask [as invoke] (zone.js:487)

The function looks like this:

openAddLocation() {
this.popover
  .create({
    component: LocationAddPage,
    cssClass: '',
    showBackdrop: true,
  })
  .then((popoverElement) => {
    popoverElement.present();
  });

}

I have another popover which works fine but it is triggered in the same page.

header.component.ts

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

@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.scss'],
})
export class HeaderComponent implements OnInit {
  @Input() title: string;
  @Input() openAddLocation: Function;
  showBackBtn: boolean = false;
  showMenuBtn: boolean = true;
  path: string;

  constructor(private router: Router) {}

  ngOnInit() {
    this.path = this.router.url;
    if (/labsite-selection|retailers|location-selection/.test(this.path)) {
      this.showBackBtn = true;
      this.showMenuBtn = false;
    } else {
      this.showBackBtn = false;
      this.showMenuBtn = true;
    }
  }
}

components.module.ts

import { NgModule } from '@angular/core';
import { IonicModule } from '@ionic/angular';
import { CommonModule } from '@angular/common';
import { FormsModule } from '@angular/forms';
import { HeaderComponent } from './header/header.component';
import { SearchComponent } from './search/search.component';

@NgModule({
  imports: [IonicModule, CommonModule, FormsModule],
  declarations: [HeaderComponent, SearchComponent],
  exports: [HeaderComponent, SearchComponent],
  providers: [],
})
export class ComponentsModule {}

header.component.html

<ion-header mode="md">
  <ion-toolbar color="primary">
    <ion-title>{{ title }}</ion-title>
    <ion-buttons slot="start">
      <ion-menu-button *ngIf="showMenuBtn" autoHide="false"></ion-menu-button>
      <ion-back-button
        *ngIf="showBackBtn"
        defaultHref="start"
      ></ion-back-button>
    </ion-buttons>
    <ion-buttons
      *ngIf="path.includes('location-selection')"
      slot="end"
      (click)="openAddLocation()"
    >
      <ion-button>
        <ion-icon slot="icon-only" name="add-outline"></ion-icon>
      </ion-button>
    </ion-buttons>
  </ion-toolbar>
</ion-header>

You should register your popover for each component where do you use it. — Danil Prokhorenko
– Danil Prokhorenko, Commented Jul 17, 2021 at 0:27
@Danil I registered the popover in the page module and the component module (where all components are registered) and also in the popover page itself ofc — kdc
– kdc, Commented Jul 17, 2021 at 12:53
@kdc Can you add the code of the component (with imports and declarations) which produces the error? — Danil Prokhorenko
– Danil Prokhorenko, Commented Jul 17, 2021 at 13:00

Danil Prokhorenko · Accepted Answer · 2021-07-18 00:09:32Z

First of all, solution. You use your app-header component in this way:

<app-header [openAddLocation]="openAddLocation"></app-header>

and you have in your page this code:

openAddLocation() {
    this.popover.create({
        component: LocationAddPage,
        cssClass: '',
        showBackdrop: true,
    }).then((popoverElement) => {
        popoverElement.present();
    });
}

You should change it to this:

openAddLocation = () => {
    this.popover.create({
        component: LocationAddPage,
        cssClass: '',
        showBackdrop: true,
    }).then((popoverElement) => {
        popoverElement.present();
    });
}

Explanation:

In the first case, you pass a Function. This method does not pass this context to the component. When the component tries to call @Input function It calls with this of the component but not this of the page.

In the second case, you pass a closure. And here will uses this of the page in both calls.

Another solution

I think the first solution is easy to implement for you but I don't think that this is a good approach. I think It will be better to use @Output params instead of @Input to call the function.

In your header.component.ts:

- import { Component, Input, OnInit } from '@angular/core';
+ import { Component, EventEmitter, Input, Output, OnInit } from '@angular/core';

- @Input() openAddLocation: Function;
+ @Output() openAddLocation: EventEmitter<void> = new EventEmitter();

header.component.html:

- (click)="openAddLocation()"
+ (click)="openAddLocation.emit()"

Then you can use it on your page in this way:

<app-header (openAddLocation)="openAddLocation()"></app-header>

More info about @Input and @Output params in documentation: https://angular.io/guide/inputs-outputs

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