如何将 object 从服务传递到 Angular8 中的组件？

Question

I have a problem i want to pass an object list from a service to a component. the response is undefined.

This is the :

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

@Injectable({
  providedIn: 'root',
})
export class DataService {
  public data: {
    "first": [
      {
        list: 'first';
        id: 1;
        title: 'First list title item';
        description?: 'Example description for first list title item';
        completed: false;
      }
    ],
    "second": [
      {
        list: 'second'
        id: 2;
        title: 'Second list title item';
        description?: 'Example description for second list title item';
        completed: false;
      }
    ],
    "third": [
      {
        list: 'third'
        id: 2;
        title: 'Third list title item';
        description?: 'Example description for third list title item';
        completed: false;
      }
    ],
  };
  loadAll(){
    return this.data;
  }
}

This is the ts of component

import { Component, OnInit } from '@angular/core';
import { DataService } from '../service/data-service.service';

@Component({
  selector: 'app-todo-item',
  templateUrl: './view-item.component.html',
  styleUrls: ['./view-item.component.scss'],
})

export class ViewItemComponent implements OnInit {
  todos: {};
  constructor(private dataService: DataService) {}

  ngOnInit() {
    this.todos = this.dataService;
    this.dataService.loadAll();
    console.log(this.dataService.data);
  }
}

for now I need only the console.log of the object.

Thanks!

Answer 1

There are a bunch of syntax errors in your code.

1) You aren't assigning anything to data in your service.

2) The keys/properties should be separated by comma, not semicolon.

This should fix it.

On your data-service.service.ts,

@Injectable()
export class DataService {
  public data = {
    "first": [
      {
        list: 'first',
        id: 1,
        title: 'First list title item',
        description: 'Example description for first list title item',
        completed: false,
      }
    ],
    "second": [
      {
        list: 'second',
        id: 2,
        title: 'Second list title item',
        description: 'Example description for second list title item',
        completed: false,
      }
    ],
    "third": [
      {
        list: 'third',
        id: 2,
        title: 'Third list title item',
        description: 'Example description for third list title item',
        completed: false,
      }
    ],
  };
  loadAll(){
    return this.data;
  }
}

And on your component.ts, you should assign the values returned by the loadAll() method from your service into a variable or property in your component.

import { Component, OnInit } from '@angular/core';
import { DataService } from '../service/data-service.service';

@Component({
  selector: 'app-todo-item',
  templateUrl: './view-item.component.html',
  styleUrls: ['./view-item.component.scss'],
})

export class ViewItemComponent implements OnInit {
  todos;
  constructor(private dataService: DataService) {}

  ngOnInit() {
    this.todos = this.dataService.loadAll();
    console.log(this.todos);
  }
}

I have reproduced a demo over here .