Observar tipos de mudanças com listeners de monitoramento do Firestore

Observar tipos de mudanças com listeners de monitoramento do Firestore

Páginas de documentação que incluem esta amostra de código

Para visualizar o exemplo de código usado em contexto, consulte a seguinte documentação:

Exemplo de código

Go

import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/firestore"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// listenChanges listens to a query, returning the list of document changes.
func listenChanges(ctx context.Context, w io.Writer, projectID, collection string) error {
	// projectID := "project-id"
	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	client, err := firestore.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("firestore.NewClient: %v", err)
	}
	defer client.Close()

	it := client.Collection(collection).Where("state", "==", "CA").Snapshots(ctx)
	for {
		snap, err := it.Next()
		// DeadlineExceeded will be returned when ctx is cancelled.
		if status.Code(err) == codes.DeadlineExceeded {
			return nil
		}
		if err != nil {
			return fmt.Errorf("Snapshots.Next: %v", err)
		}
		if snap != nil {
			for _, change := range snap.Changes {
				switch change.Kind {
				case firestore.DocumentAdded:
					fmt.Fprintf(w, "New city: %v\n", change.Doc.Data())
				case firestore.DocumentModified:
					fmt.Fprintf(w, "Modified city: %v\n", change.Doc.Data())
				case firestore.DocumentRemoved:
					fmt.Fprintf(w, "Removed city: %v\n", change.Doc.Data())
				}
			}
		}
	}
}

Java

db.collection("cities")
    .whereEqualTo("state", "CA")
    .addSnapshotListener(new EventListener<QuerySnapshot>() {
      @Override
      public void onEvent(@Nullable QuerySnapshot snapshots,
                          @Nullable FirestoreException e) {
        if (e != null) {
          System.err.println("Listen failed: " + e);
          return;
        }

        for (DocumentChange dc : snapshots.getDocumentChanges()) {
          switch (dc.getType()) {
            case ADDED:
              System.out.println("New city: " + dc.getDocument().getData());
              break;
            case MODIFIED:
              System.out.println("Modified city: " + dc.getDocument().getData());
              break;
            case REMOVED:
              System.out.println("Removed city: " + dc.getDocument().getData());
              break;
            default:
              break;
          }
        }
      }
    });

Node.js

const observer = db.collection('cities').where('state', '==', 'CA')
  .onSnapshot(querySnapshot => {
    querySnapshot.docChanges().forEach(change => {
      if (change.type === 'added') {
        console.log('New city: ', change.doc.data());
      }
      if (change.type === 'modified') {
        console.log('Modified city: ', change.doc.data());
      }
      if (change.type === 'removed') {
        console.log('Removed city: ', change.doc.data());
      }
    });
  });

Python


# Create an Event for notifying main thread.
delete_done = threading.Event()

# Create a callback on_snapshot function to capture changes
def on_snapshot(col_snapshot, changes, read_time):
    print(u'Callback received query snapshot.')
    print(u'Current cities in California: ')
    for change in changes:
        if change.type.name == 'ADDED':
            print(f'New city: {change.document.id}')
        elif change.type.name == 'MODIFIED':
            print(f'Modified city: {change.document.id}')
        elif change.type.name == 'REMOVED':
            print(f'Removed city: {change.document.id}')
            delete_done.set()

col_query = db.collection(u'cities').where(u'state', u'==', u'CA')

# Watch the collection query
query_watch = col_query.on_snapshot(on_snapshot)

Ruby

query = firestore.col(collection_path).where :state, :==, "CA"
added = []
modified = []
removed = []

# Watch the collection query.
listener = query.listen do |snapshot|
  puts "Callback received query snapshot."
  puts "Current cities in California:"
  snapshot.changes.each do |change|
    if change.added?
      puts "New city: #{change.doc.document_id}"
      added << snapshot
    elsif change.modified?
      puts "Modified city: #{change.doc.document_id}"
      modified << snapshot
    elsif change.removed?
      puts "Removed city: #{change.doc.document_id}"
      removed << snapshot
    end
  end
end

A seguir

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