Question

我有一个待办事项列表，并希望按诸如“ author / dateOfCreate / deadline ..”等类别对其进行排序。我在第一次使用Firebase orderBy（'property_name'）方法时在构造函数中调用它-它可以工作，但是当我尝试在下面的函数中传递不同的'property_name'时，它却没有。我对此并不陌生，因此将为您提供任何建议。这是我的代码：

export interface Todo {
  id?: string,
  author?: string,  
  completed?: boolean,   
  dateOfCreate?: number,  
  deadline?: number,  
  todoDescription?: string  
}

TodoService

import { Injectable } from '@angular/core';
import { AngularFirestore, AngularFirestoreCollection, AngularFirestoreDocument
} from '@angular/fire/firestore';
import { Todo } from '../models/todo'
import { Observable } from 'rxjs';
import { map, filter } from 'rxjs/operators';


@Injectable({ providedIn: 'root' })
export class TodosService {
  todoCollection: AngularFirestoreCollection<Todo>
  todos: Observable<Todo[]>
  sort: string= 'deadline'

  constructor(public afs: AngularFirestore) {
    console.log(this.afs.collection('todos'))
    this.todoCollection = this.afs.collection('todos', ref => ref.orderBy(this.sort, 'desc'))
    this.todos = this.todoCollection.snapshotChanges().pipe(
      map(changes => {
        return changes.map(a => {
          const data = a.payload.doc.data() as Todo
          data.id = a.payload.doc.id
          return data
        })
      })
    )
  }

  getTodos() {
    return this.todos
  }

  sortByAuthor(){
    return this.sort = 'author'
  }
}

Todo.component.ts

constructor(private todoService: TodosService) { }

sortbyAuthor() {
  this.todoService.sortByAuthor()
}

Todo.component.html

<button (click)="sortbyAuthor()">Author</button>

Answer 1

调用sortByAuthor()时，查询未在运行，您只是将author分配给this.sort。这就是为什么没有变化的原因。您可以将服务类更改为以下内容：

@Injectable({ providedIn: 'root' })
export class TodosService {
  todoCollection: AngularFirestoreCollection<Todo>
  todos: Observable<Todo[]>
  sort: string= 'deadline'

  constructor(public afs: AngularFirestore) {
    console.log(this.afs.collection('todos'));
  }

  getCollection(sort : string){
    this.todoCollection = this.afs.collection('todos', ref => ref.orderBy(this.sort, 'desc'))
    this.todos = this.todoCollection.snapshotChanges().pipe(
      map(changes => {
        return changes.map(a => {
          const data = a.payload.doc.data() as Todo
          data.id = a.payload.doc.id
          return data
        })
      })
    )
  }

  getTodos() {
    return this.todos
  }

  sortByAuthor(){
    this.sort = 'author';
    return this.getCollection(this.sort);
  }
}

在Firebase（角度）中对数据进行排序

1 个答案: