How to access variables of one component in another component [Angular]

Question

I'm new to Angular. I'm trying a simple thing today. I've gone through many answers but not able implement them correctly. I want to access some variables of filter-panel in filter-bar, (my two custom components). But none of the two is parent-child to each other. They're independent, though within the same directory. Here I've created a stackblitz. And here's my code:

filter-panel.component.ts

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

@Component({
    ...
})
export class FilterPanelComponent implements OnInit {

public activeFilters: string[];
public text: string="hello world";

constructor() {
    this.activeFilters = [
        'Apple',
        'Grapes',
        'Bana'
    ];
}

ngOnInit() {}

}

filter-bar.component.ts

import { Component, OnInit, ViewChild } from '@angular/core';
import { FilterPanelComponent } from './filter-panel/filter-panel.component';

@Component({
    ...
})
export class FilterBarComponent implements OnInit {

    @ViewChild('FilterPanelComponent', {static : false}) filterPanel: FilterPanelComponent;

    public values1: string[] = ['Philips'];

    public values2: string[];

    constructor() {
      //this.values2=this.filterPanel.activeFilters;  
    }

    ngOnInit() {
        //console.log(this.values2);
    }
}

After doing some more research I realized it's pointless to use @ViewChild in this scenario. So I tried making a service. I tried @Input(). I also tried this: How to use a variable from a component in another in Angular2. but I'm still not able to implement the solution. Please correct me.

Answer 1

You can create a service to share the data between components,

A new service called, filter-panel.service.ts file with setter() and getter() method,

import { Injectable } from '@angular/core';

@Injectable()
export class FilterPanelService {

  filterdata: any[];
  constructor() { }

   get data(): any{
    return this.filterdata;
  }

  set data(val: any){
    this.filterdata = val;
    console.log(this.filterdata);
  }

}

In filter-panel.component.ts set the value like,

export class FilterPanelComponent implements OnInit {

    public activeFilters: string[];
    public text: string="hello world";

    constructor(public filterPanelService:FilterPanelService) {

        this.activeFilters = [
            'Provider: CMS',
            'Region: All',
            'Provider Group:All',
            'Provider: CMS',
            'Region: All',
            'Provider Group: All'
        ];

        this.filterPanelService.data = this.activeFilters;
    }

    ngOnInit() {}
}

And in filter-bar.component.ts get the value like,

export class FilterBarComponent implements OnInit {
    @ViewChild('FilterPanelComponent', {static : false}) filterPanel: FilterPanelComponent;


    public values1: string[] = ['Philips'];

    public values2: string[];


    constructor(public filterPanelService: FilterPanelService) {

      //this.values2=this.filterPanel.activeFilters;  
    }

    ngOnInit() {
        //console.log(this.values2);
        console.log('value received ', this.filterPanelService.data);
    }
}

Working Stackblitz..

Answer 2

If both component don't have parent child relationship and if you want to pass the data between them then you can implement the RxJS subject for the same. I hope it helps you out

Message Service

import { Injectable } from '@angular/core';
import { Observable, Subject } from 'rxjs';

@Injectable({ providedIn: 'root' })
export class MessageService {
    private subject = new Subject<any>();

    sendMessage(message: string) {
        this.subject.next({ text: message });
    }

    clearMessages() {
        this.subject.next();
    }

    getMessage(): Observable<any> {
        return this.subject.asObservable();
    }
}

filter-panel.component.ts

import { Component, OnInit } from '@angular/core';
import { messageService } from '../MesssageService.ts'
@Component({
    ...
})
export class FilterPanelComponent implements OnInit {

public activeFilters: string[];
public text: string="hello world";

constructor(private messageService: MessageService) {
    this.activeFilters = [
        'Apple',
        'Grapes',
        'Bana'
    ];
 }

ngOnInit() {}
     this.messageService.sendMessage('data from filterPanelComponent'); // here you can also pass the object 
}

filter-bar.component.ts

import { Component, OnInit, ViewChild } from '@angular/core';
import { messageService } from '../MesssageService.ts'

@Component({
    ...
})
export class FilterBarComponent implements OnInit {

    constructor(private messageService: MessageService) {

    }

    ngOnInit() {
     this.messageService.getMessage().subscribe(response => {
     // here we get the data from another component
      console.log(response);
     })
    }
}