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listen_multiple.go
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listen_multiple.go
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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
// [START firestore_listen_query_snapshots]
import (
"context"
"fmt"
"io"
"time"
"cloud.google.com/go/firestore"
"google.golang.org/api/iterator"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
)
// listenMultiple listens to a query, returning the names of all cities
// for a state.
func listenMultiple(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 {
doc, err := snap.Documents.Next()
if err == iterator.Done {
break
}
if err != nil {
return fmt.Errorf("Documents.Next: %v", err)
}
fmt.Fprintf(w, "Current cities in California: %v\n", doc.Ref.ID)
}
}
}
}
// [END firestore_listen_query_snapshots]