如何解决 - 属性'then'在类型 'Subscription' 上不存在

Question

我在其函数中写下了put和删除方法（分别为" editform"one_answers" deleteform"）。

我想在成功完成每个请求后显示setAlert()功能。因此，我使用了.then()方法，并且它在editForm功能中正常工作，如下所示。

但是当我为 deleteForm做同样的事情时， .then()方法不起作用，因为它说："然后'然后在类型'订阅'上不存在'。那么我该如何解决？

这是我的component.ts文件：

import { Component, OnInit, OnDestroy } from '@angular/core';
import { ActivatedRoute, Router } from '@angular/router';
import { FormService } from './forms.service';
import { HttpClient } from '@angular/common/http';
import { alert } from './alert';
@Component({
  selector: 'app-forms',
  templateUrl: './forms.component.html',
  styleUrls: ['./forms.component.css']
})

export class FormsComponent implements OnInit {
  alert: alert;
  id: any;
  posts: any;
  constructor(public formService: FormService ,private route: ActivatedRoute,
    private router: Router, private http: HttpClient) { }

  ngOnInit() {
    this.id=this.route.snapshot.params['id'];
    this.alert = new alert();
    this.posts = this.formService.getForms(this.id).subscribe(
      (forms: any) => {
        this.formService.form = forms[0];
      }
    );
  }
  editPost() {
    this.formService.editForm().then((res:any) => {
      this.formService.alert.setAlert("Post has been successfully saved !");
    })
  }
  deletePost() {
    this.formService.deleteForm().subscribe(
      data  => {
        console.log("DELETE Request is successful ", data);
      },
      error  => {
        console.log("Error", error);
      }
    ).then(() => {
      this.formService.alert.setAlert("Post has been successfully deleted !");
    })
  }
}

这是我的service.ts文件：

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { form } from './form-interface';
import { alert } from './alert';

@Injectable({
    providedIn: 'root'
}) 
export class FormService {
  formsUrl = "https://jsonplaceholder.typicode.com/posts";
  form: form = {
      id: 0,
      userId: 0,
      title: '',
      body: ''
  };
  alert: alert;

    constructor(private http: HttpClient) { 
      this.alert = new alert();
    }
    getForms(id) {
            return this.http.get('https://jsonplaceholder.typicode.com/posts'
            + "?id=" + id)
    }
    editForm() {
        return fetch(this.formsUrl + "/" + this.form.id, {
          method: 'PUT',
          body: JSON.stringify(this.form),
          headers: {
            "Content-type": "application/json; charset=UTF-8"
          }
        })
        .then(response => response.json())
    }
    deleteForm() {
        return this.http.delete(this.formsUrl + "/" + this.form.id);
      }
}

Answer 1

editform方法使用JavaScript fetch API调用服务，该服务返回了Promise SO then方法在此处工作。在deleteForm方法中，您是使用Angular HttpClient进行的服务调用，该呼叫可返回可观察的。而不是使用then，您应该使用subscribe方法

deleteForm() {
        return this.http.delete(this.formsUrl + "/" + this.form.id);
}

在您的component.ts

中

 deletePost() {
    this.formService.deleteForm().subscribe(
      data  => {
        console.log("DELETE Request is successful ", data);
        this.formService.alert.setAlert("Post has been successfully deleted !");
      },
      error  => {
        console.log("Error", error);
      }
    )
  }

Answer 2

，因为http返回可观察到的不承诺。在此处使用.subscribe。它将解决您的问题

Answer 3

当您在订阅方法中获取响应并将警报调用时，您可以使用消息如下

deletePost() {
this.formService.deleteForm().subscribe(
  data  => {
    console.log("DELETE Request is successful ", data);
    this.formService.alert.setAlert("Post has been successfully deleted !");
  },
  error  => {
    console.log("Error", error);
  }
))

}