mean-stack - 数据更改后Angular UI不更新

Question

我是 MEAN 堆栈的新手，无法在 UI 中刷新数据更改。我知道数据在 MongoDB 中正确保存，并且也被检索，因为当我创建一个 Todo 项并刷新页面时，新添加的 Todo 项出现在 Todo 列表中。问题是它不是动态发生的。

我尝试了许多不同的方法，包括 NgZone 和 ChangeDetectorRef 来检测更改，但不确定我做错了什么。

如果需要更多信息，请告诉我。谢谢！

待办事项列表组件：

import { Component, Input, OnInit, NgZone } from '@angular/core';
import { Todo } from '../todo.model';
import { TodoService } from '../../todo.service';

@Component({
selector: 'app-todo-list',
templateUrl: './todo-list.component.html',
styleUrls: ['./todo-list.component.scss'],
providers: [TodoService]
})
export class TodoListComponent implements OnInit {

@Input() todos: Todo[] = [];

constructor(private _todoService: TodoService, private zone: NgZone){}

getTodos() {
    console.log('todo list - get todos');
    this._todoService.getTodos()
        .subscribe(resTodoData => {
            this.zone.run(() => {
                this.todos = resTodoData;
            });
        });
}

ngOnInit() {
    console.log('todo list - init');
    this.getTodos();
}
}

服务组件：

import { Injectable, NgZone } from '@angular/core';
import { Http, Response, Headers, RequestOptions } from 
'@angular/http';

import { map } from 'rxjs/operators';
import { Todo } from './todos/todo.model';

 @Injectable({
     providedIn: 'root'
  })
 export class TodoService {

// these were configured in express server
private _getUrl = "/api/todos";
private _postUrl = "/api/todo";

constructor(private _http: Http, private zone: NgZone) { }

getTodos() {

    let json = this._http.get(this._getUrl)
        .pipe(map((response: Response) => response.json()));
    return json;    
}

addTodo(todo: Todo) {
    let headers = new Headers({ 'Content-Type': 'application/json' 
    });
    let options = new RequestOptions({ headers: headers });
    return this._http.post(this._postUrl, JSON.stringify(todo), 
               options)
        .pipe(map((response: Response) => response.json()));
  }
}

标签： mean-stackangular7