javascript - TypeScript/RxJS - 可观察的订阅()方法完成()未运行

Question

我环顾四周试图解决这个问题，但找不到有效的答案。

当 subscribe() 方法成功返回“contacts$”可观察对象时，我正在尝试为附加函数实现回调，但在订阅上使用 complete() 不会执行任何操作。

我也试过按照其他地方的建议在可观察对象上使用 finally()，但这也不起作用。

使用 complete():

ngOnInit() {
    this.getContacts().subscribe(
        data => {
            this.contacts = data;
            console.log('NewInvoice.contacts:', data);
            this.selectedContactId = this.contacts[0].id;
            console.log('selectedContactId: ' + this.selectedContactId);
        },
        error => {
            console.error('Error getting contacts via subscribe() method:', error);
        },
        () => {
            this.getSelectedContact();
        }
    )
}

使用 finally():

ngOnInit() {
    this.getContacts()
        .finally(() => console.log('a'))
        .subscribe(
            data => {
                this.contacts = data;
                console.log('NewInvoice.contacts:', data);
                this.selectedContactId = this.contacts[0].id;
                console.log('selectedContactId: ' + this.selectedContactId);
            },
            error => {
                console.error('Error getting contacts via subscribe() method:', error);
            },
            () => {
                this.getSelectedContact();
            }
    )
}

可观察完成的回调方法:

getSelectedContact() {
    this.contactsCollection.doc(this.selectedContactId).ref.get().then(snapshot => {
        this.selectedContact = snapshot.data() as Contact;
        console.log('selectedContact:', this.selectedContact);
    })
}

Answer 1

没有更多信息很难说，但我会试一试:

  ngOnInit() {
    this.getContacts()
      .subscribe(
        data => {
          this.contacts = data;
          console.log('NewInvoice.contacts:', data);
          this.selectedContactId = this.contacts[0].id;
          console.log('selectedContactId: ' + this.selectedContactId);
        },
        error => {
          console.error('Error getting contacts via subscribe() method:', error);
        },
        () => {
          this.getSelectedContact()
            .asObservable()
            .subscribe((a) => console.log(a));
        }
      )
  }

和:

getSelectedContact() {
    return this.contactsCollection.doc(this.selectedContactId).ref.get().then(snapshot => {
        this.selectedContact = snapshot.data() as Contact;
        console.log('selectedContact:', this.selectedContact);
    })
}

或者更干净一些:

    const callback = (a) => console.log(a);
  ...
    () => {
      this.getSelectedContact(callback);
    }
  ...
    getSelectedContact(callback) {
      this.contactsCollection.doc(this.selectedContactId).ref.get()
        .then(snapshot => {
          this.selectedContact = snapshot.data() as Contact;
          console.log('selectedContact:', this.selectedContact);
        })
        .then(a => callback(a));
    }

最后正如@Picci 建议的那样:

this.getContacts()
    .last()
    .exhaustMap((data) => this.getSelectedContact(data))
    .map(a => console.log(a))
    .subscribe();

请注意，以上所有代码均未经过绝对测试，仅供引用。