问角形:为什么我不能使用组件的一个方法作为一个可观察的回调来更新组件中的属性？

EN

import { Component, OnInit } from '@angular/core';
import { BlogService } from '../blog.service';
import { Blog } from '../blog';
import { Observable, of } from 'rxjs';

@Component({
  selector: 'app-articles',
  templateUrl: './articles.component.html',
  styleUrls: ['./articles.component.css']
})
export class ArticlesComponent implements OnInit {
  blogs: Blog[];
  constructor(private blogService: BlogService) { }

  ngOnInit() {
    // const handler = (incomingBlogs: Blog[]) => {
    //   this.blogs = incomingBlogs;
    //   console.log("we get: ", this.blogs);
    // }

    const observable: Observable<Blog[]> = this.blogService.getBlogs();
    // observable.subscribe(handler); <===== this will work
    // observable.subscribe(incomingBlogs => {this.blogs = incomingBlogs;  console.log("fat get: ", this.blogs);}); <====== this also work
    observable.subscribe(this.handler); // <===== this failed. 
    console.log("this in init", this);
  }

  handler(incomingBlogs: Blog[]) {
    this.blogs = incomingBlogs;
    console.log("we get: ", this.blogs);
    console.log("this in handler", this); //seems the this keyword refers to something different than the object itself.
  }

}