如何在angularfire2中查询

Question

while using angularfire in my project i didnt know what to write exactly to get the name bellow MY BD

i really need help, i want the query that gives me back the key of the item where name="om" for example thanks !

Answer 1

What you're trying to do here is, Query Lists Just have a look at the Docs and you should be on your way.

Here's a simple example to get you started:

import { Component } from '@angular/core';
import { AngularFireDatabase } from '@angular/fire/database';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  users;

  constructor(private db: AngularFireDatabase) {}

  ngOnInit() {
    this.db.list('/Users', ref => ref.orderByChild('name').equalTo('Om'))
      .snapshotChanges()
      .subscribe((snapshot: any) => this.users = snapshot.map(snap => ({ ...snap })));
  }

}

And in the Template:

<pre>{{ users | json }}</pre>

This will return an array. So you'll have to make sure that the field that you're querying is unique if you want only one item.

Also, this sort of query will download the whole data on the client. So you'd get a warning saying:

@firebase/database: FIREBASE WARNING: Using an unspecified index. Your data will be downloaded and filtered on the client. Consider adding ".indexOn": "name" at /Users to your security rules for better performance.

To fix that, update your security rules like this:

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null",
    "Users": {
      ".indexOn": [
        "name"
      ]
    }
  }
}

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Here's a Working Sample StackBlitz for your ref.