Como receber dados com o Cloud Firestore

Há duas maneiras de recuperar dados armazenados no Cloud Firestore. Qualquer um desses métodos pode ser usado com documentos, coleções de documentos ou os resultados de consultas:

  • Chame um método para receber os dados.
  • Defina um listener para receber eventos de mudança de dados.

Quando você configura um listener, o Cloud Firestore envia para ele um instantâneo inicial dos dados e, em seguida, outro instantâneo cada vez que o documento é alterado.

Dados de exemplo

Para começar, escreva alguns dados sobre cidades para demonstrarmos diversas formas de leitura:

Web
var citiesRef = db.collection("cities");

citiesRef.doc("SF").set({
    name: "San Francisco", state: "CA", country: "USA",
    capital: false, population: 860000 });
citiesRef.doc("LA").set({
    name: "Los Angeles", state: "CA", country: "USA",
    capital: false, population: 3900000 });
citiesRef.doc("DC").set({
    name: "Washington, D.C.", state: null, country: "USA",
    capital: true, population: 680000 });
citiesRef.doc("TOK").set({
    name: "Tokyo", state: null, country: "Japan",
    capital: true, population: 9000000 });
citiesRef.doc("BJ").set({
    name: "Beijing", state: null, country: "China",
    capital: true, population: 21500000 });
Swift
let citiesRef = db.collection("cities")

citiesRef.document("SF").setData([
    "name": "San Francisco",
    "state": "CA",
    "country": "USA",
    "capital": false,
    "population": 860000
    ])
citiesRef.document("LA").setData([
    "name": "Los Angeles",
    "state": "CA",
    "country": "USA",
    "capital": false,
    "population": 3900000
    ])
citiesRef.document("DC").setData([
    "name": "Washington D.C.",
    "country": "USA",
    "capital": true,
    "population": 680000
    ])
citiesRef.document("TOK").setData([
    "name": "Tokyo",
    "country": "Japan",
    "capital": true,
    "population": 9000000
    ])
citiesRef.document("BJ").setData([
    "name": "Beijing",
    "country": "China",
    "capital": true,
    "population": 21500000
    ])
Objective-C
FIRCollectionReference *citiesRef = [self.db collectionWithPath:@"cities"];
[[citiesRef documentWithPath:@"SF"] setData:@{
  @"name": @"San Francisco",
  @"state": @"CA",
  @"country": @"USA",
  @"capital": @(NO),
  @"population": @860000
}];
[[citiesRef documentWithPath:@"LA"] setData:@{
  @"name": @"Los Angeles",
  @"state": @"CA",
  @"country": @"USA",
  @"capital": @(NO),
  @"population": @3900000
}];
[[citiesRef documentWithPath:@"DC"] setData:@{
  @"name": @"Washington D.C.",
  @"country": @"USA",
  @"capital": @(YES),
  @"population": @680000
}];
[[citiesRef documentWithPath:@"TOK"] setData:@{
  @"name": @"Tokyo",
  @"country": @"Japan",
  @"capital": @(YES),
  @"population": @9000000
}];
[[citiesRef documentWithPath:@"BJ"] setData:@{
  @"name": @"Beijing",
  @"country": @"China",
  @"capital": @(YES),
  @"population": @21500000
}];
  
Android
CollectionReference cities = db.collection("cities");

Map<String, Object> data1 = new HashMap<>();
data1.put("name", "San Francisco");
data1.put("state", "CA");
data1.put("country", "USA");
data1.put("capital", false);
data1.put("population", 860000);
cities.document("SF").set(data1);

Map<String, Object> data2 = new HashMap<>();
data2.put("name", "Los Angeles");
data2.put("state", "CA");
data2.put("country", "USA");
data2.put("capital", false);
data2.put("population", 3900000);
cities.document("LA").set(data2);

Map<String, Object> data3 = new HashMap<>();
data3.put("name", "Washington D.C.");
data3.put("state", null);
data3.put("country", "USA");
data3.put("capital", true);
data3.put("population", 680000);
cities.document("DC").set(data3);

Map<String, Object> data4 = new HashMap<>();
data4.put("name", "Tokyo");
data4.put("state", null);
data4.put("country", "Japan");
data4.put("capital", true);
data4.put("population", 9000000);
cities.document("TOK").set(data4);

Map<String, Object> data5 = new HashMap<>();
data5.put("name", "Beijing");
data5.put("state", null);
data5.put("country", "China");
data5.put("capital", true);
data5.put("population", 21500000);
cities.document("BJ").set(data5);
Java
CollectionReference cities = db.collection("cities");
List<ApiFuture<WriteResult>> futures = new ArrayList<>();
futures.add(cities.document("SF").set(new City("San Francisco", "CA", "USA", false, 860000L)));
futures.add(cities.document("LA").set(new City("Los Angeles", "CA", "USA", false, 3900000L)));
futures.add(cities.document("DC").set(new City("Washington D.C.", null, "USA", true, 680000L)));
futures.add(cities.document("TOK").set(new City("Tokyo", null, "Japan", true, 9000000L)));
futures.add(cities.document("BJ").set(new City("Beijing", null, "China", true, 21500000L)));
// (optional) block on operation
ApiFutures.allAsList(futures).get();
Python
class City(object):
    def __init__(self, name, state, country, capital=False, population=0):
        self.name = name
        self.state = state
        self.country = country
        self.capital = capital
        self.population = population

    @staticmethod
    def from_dict(source):
        # ...

    def to_dict(self):
        # ...

    def __repr__(self):
        return u'City(name={}, country={}, population={}, capital={})'.format(
            self.name, self.country, self.population, self.capital)

cities_ref = db.collection(u'cities')
cities_ref.document(u'SF').set(
    City(u'San Francisco', u'CA', u'USA', False, 860000).to_dict())
cities_ref.document(u'LA').set(
    City(u'Los Angeles', u'CA', u'USA', False, 3900000).to_dict())
cities_ref.document(u'DC').set(
    City(u'Washington D.C.', None, u'USA', True, 680000).to_dict())
cities_ref.document(u'TOK').set(
    City(u'Tokyo', None, u'Japan', True, 9000000).to_dict())
cities_ref.document(u'BJ').set(
    City(u'Beijing', None, u'China', True, 21500000).to_dict())
Node.js
var citiesRef = db.collection('cities');

var setSf = citiesRef.doc('SF').set({
    name: 'San Francisco', state: 'CA', country: 'USA',
    capital: false, population: 860000 });
var setLa = citiesRef.doc('LA').set({
    name: 'Los Angeles', state: 'CA', country: 'USA',
    capital: false, population: 3900000 });
var setDc = citiesRef.doc('DC').set({
    name: 'Washington, D.C.', state: null, country: 'USA',
    capital: true, population: 680000 });
var setTok = citiesRef.doc('TOK').set({
    name: 'Tokyo', state: null, country: 'Japan',
    capital: true, population: 9000000 });
var setBj = citiesRef.doc('BJ').set({
    name: 'Beijing', state: null, country: 'China',
    capital: true, population: 21500000 });
Go
cities := []struct {
	id string
	c  City
}{
	{id: "SF", c: City{Name: "San Francisco", State: "CA", Country: "USA", Capital: false, Population: 860000}},
	{id: "LA", c: City{Name: "Los Angeles", State: "CA", Country: "USA", Capital: false, Population: 3900000}},
	{id: "DC", c: City{Name: "Washington D.C.", Country: "USA", Capital: false, Population: 680000}},
	{id: "TOK", c: City{Name: "Tokyo", Country: "Japan", Capital: true, Population: 9000000}},
	{id: "BJ", c: City{Name: "Beijing", Country: "China", Capital: true, Population: 21500000}},
}
for _, c := range cities {
	_, err := client.Collection("cities").Doc(c.id).Set(ctx, c.c)
	if err != nil {
		return err
	}
}
PHP
$citiesRef = $db->collection('cities');
$citiesRef->document('SF')->set([
    'name' => 'San Francisco',
    'state' => 'CA',
    'country' => 'USA',
    'capital' => false,
    'population' => 860000
]);
$citiesRef->document('LA')->set([
    'name' => 'Los Angeles',
    'state' => 'CA',
    'country' => 'USA',
    'capital' => false,
    'population' => 3900000
]);
$citiesRef->document('DC')->set([
    'name' => 'Washington D.C.',
    'state' => null,
    'country' => 'USA',
    'capital' => true,
    'population' => 680000
]);
$citiesRef->document('TOK')->set([
    'name' => 'Tokyo',
    'state' => null,
    'country' => 'Japan',
    'capital' => true,
    'population' => 9000000
]);
$citiesRef->document('BJ')->set([
    'name' => 'Beijing',
    'state' => null,
    'country' => 'China',
    'capital' => true,
    'population' => 21500000
]);
printf('Added example cities data to the cities collection.' . PHP_EOL);

Receber um documento

O exemplo a seguir mostra como recuperar o conteúdo de um único documento usando get():

Web
var docRef = db.collection("cities").doc("SF");

docRef.get().then(function(doc) {
    if (doc.exists) {
        console.log("Document data:", doc.data());
    } else {
        // doc.data() will be undefined in this case
        console.log("No such document!");
    }
}).catch(function(error) {
    console.log("Error getting document:", error);
});
Swift
let docRef = db.collection("cities").document("SF")

docRef.getDocument { (document, error) in
    if let document = document, document.exists {
        let dataDescription = document.data().map(String.init(describing:)) ?? "nil"
        print("Document data: \(dataDescription)")
    } else {
        print("Document does not exist")
    }
}
Objective-C
FIRDocumentReference *docRef =
    [[self.db collectionWithPath:@"cities"] documentWithPath:@"SF"];
[docRef getDocumentWithCompletion:^(FIRDocumentSnapshot *snapshot, NSError *error) {
  if (snapshot.exists) {
    // Document data may be nil if the document exists but has no keys or values.
    NSLog(@"Document data: %@", snapshot.data);
  } else {
    NSLog(@"Document does not exist");
  }
}];
  
Android
DocumentReference docRef = db.collection("cities").document("SF");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        if (task.isSuccessful()) {
            DocumentSnapshot document = task.getResult();
            if (document.exists()) {
                Log.d(TAG, "DocumentSnapshot data: " + document.getData());
            } else {
                Log.d(TAG, "No such document");
            }
        } else {
            Log.d(TAG, "get failed with ", task.getException());
        }
    }
});
Java
DocumentReference docRef = db.collection("cities").document("SF");
// asynchronously retrieve the document
ApiFuture<DocumentSnapshot> future = docRef.get();
// ...
// future.get() blocks on response
DocumentSnapshot document = future.get();
if (document.exists()) {
  System.out.println("Document data: " + document.getData());
} else {
  System.out.println("No such document!");
}
Python
doc_ref = db.collection(u'cities').document(u'SF')

try:
    doc = doc_ref.get()
    print(u'Document data: {}'.format(doc.to_dict()))
except google.cloud.exceptions.NotFound:
    print(u'No such document!')
Node.js
var cityRef = db.collection('cities').doc('SF');
var getDoc = cityRef.get()
    .then(doc => {
      if (!doc.exists) {
        console.log('No such document!');
      } else {
        console.log('Document data:', doc.data());
      }
    })
    .catch(err => {
      console.log('Error getting document', err);
    });
Go
dsnap, err := client.Collection("cities").Doc("SF").Get(ctx)
if err != nil {
	return nil, err
}
m := dsnap.Data()
fmt.Printf("Document data: %#v\n", m)
PHP
$docRef = $db->collection('cities')->document('SF');
$snapshot = $docRef->snapshot();

if ($snapshot->exists()) {
    printf('Document data:' . PHP_EOL);
    print_r($snapshot->fields());
} else {
    printf('Document %s does not exist!' . PHP_EOL, $snapshot->id());
}

Objetos personalizados

O exemplo anterior recuperou o conteúdo do documento como um mapa. No entanto, muitas vezes é mais conveniente usar um tipo de objeto personalizado em algumas linguagens. Em Adicionar dados, você definiu a classe City, usada para definir cada cidade. Você pode fazer com que seu documento volte a ser um objeto City:

Web
  // Web uses JavaScript objects
  
Swift
let docRef = db.collection("cities").document("BJ")

docRef.getDocument { (document, error) in
    if let city = document.flatMap({
      $0.data().flatMap({ (data) in
        return City(dictionary: data)
      })
    }) {
        print("City: \(city)")
    } else {
        print("Document does not exist")
    }
}
  
Objective-C
FIRDocumentReference *docRef =
[[self.db collectionWithPath:@"cities"] documentWithPath:@"BJ"];
[docRef getDocumentWithCompletion:^(FIRDocumentSnapshot *snapshot, NSError *error) {
  FSTCity *city = [[FSTCity alloc] initWithDictionary:snapshot.data];
  if (city != nil) {
    NSLog(@"City: %@", city);
  } else {
    NSLog(@"Document does not exist");
  }
}];
  
Android
DocumentReference docRef = db.collection("cities").document("BJ");
docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
    @Override
    public void onSuccess(DocumentSnapshot documentSnapshot) {
        City city = documentSnapshot.toObject(City.class);
    }
});
  
Java
DocumentReference docRef = db.collection("cities").document("BJ");
// asynchronously retrieve the document
ApiFuture<DocumentSnapshot> future = docRef.get();
// block on response
DocumentSnapshot document = future.get();
City city = null;
if (document.exists()) {
  // convert document to POJO
  city = document.toObject(City.class);
  System.out.println(city);
} else {
  System.out.println("No such document!");
}
Python
doc_ref = db.collection(u'cities').document(u'BJ')

doc = doc_ref.get()
city = City.from_dict(doc.to_dict())
print(city)
Node.js
// Node.js uses JavaScript objects
Go
dsnap, err := client.Collection("cities").Doc("BJ").Get(ctx)
if err != nil {
	return nil, err
}
var c City
dsnap.DataTo(&c)
fmt.Printf("Document data: %#v\n", c)
PHP
// Not applicable for PHP

Obter vários documentos de uma coleção

Você também pode recuperar vários documentos com uma solicitação por meio da consulta de documentos em uma coleção. Por exemplo, você pode usar where() para consultar todos os documentos que atendem a uma determinada condição e, em seguida, usar get() para recuperar os resultados:

Web
db.collection("cities").where("capital", "==", true)
    .get()
    .then(function(querySnapshot) {
        querySnapshot.forEach(function(doc) {
            // doc.data() is never undefined for query doc snapshots
            console.log(doc.id, " => ", doc.data());
        });
    })
    .catch(function(error) {
        console.log("Error getting documents: ", error);
    });
Swift
db.collection("cities").whereField("capital", isEqualTo: true)
    .getDocuments() { (querySnapshot, err) in
        if let err = err {
            print("Error getting documents: \(err)")
        } else {
            for document in querySnapshot!.documents {
                print("\(document.documentID) => \(document.data())")
            }
        }
}
Objective-C
[[[self.db collectionWithPath:@"cities"] queryWhereField:@"capital" isEqualTo:@(YES)]
    getDocumentsWithCompletion:^(FIRQuerySnapshot *snapshot, NSError *error) {
      if (error != nil) {
        NSLog(@"Error getting documents: %@", error);
      } else {
        for (FIRDocumentSnapshot *document in snapshot.documents) {
          NSLog(@"%@ => %@", document.documentID, document.data);
        }
      }
    }];
  
Android
db.collection("cities")
        .whereEqualTo("capital", true)
        .get()
        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
            @Override
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                if (task.isSuccessful()) {
                    for (QueryDocumentSnapshot document : task.getResult()) {
                        Log.d(TAG, document.getId() + " => " + document.getData());
                    }
                } else {
                    Log.d(TAG, "Error getting documents: ", task.getException());
                }
            }
        });
Java
//asynchronously retrieve multiple documents
ApiFuture<QuerySnapshot> future =
    db.collection("cities").whereEqualTo("capital", true).get();
// future.get() blocks on response
List<QueryDocumentSnapshot> documents = future.get().getDocuments();
for (DocumentSnapshot document : documents) {
  System.out.println(document.getId() + " => " + document.toObject(City.class));
}
Python
docs = db.collection(u'cities').where(u'capital', u'==', True).get()

for doc in docs:
    print(u'{} => {}'.format(doc.id, doc.to_dict()))
Node.js
var citiesRef = db.collection('cities');
var query = citiesRef.where('capital', '==', true).get()
    .then(snapshot => {
      snapshot.forEach(doc => {
        console.log(doc.id, '=>', doc.data());
      });
    })
    .catch(err => {
      console.log('Error getting documents', err);
    });
Go
fmt.Println("All capital cities:")
iter := client.Collection("cities").Where("capital", "==", true).Documents(ctx)
for {
	doc, err := iter.Next()
	if err == iterator.Done {
		break
	}
	if err != nil {
		return err
	}
	fmt.Println(doc.Data())
}
PHP
$citiesRef = $db->collection('cities');
$query = $citiesRef->where('capital', '=', true);
$documents = $query->documents();
foreach ($documents as $document) {
    if ($document->exists()) {
        printf('Document data for document %s:' . PHP_EOL, $document->id());
        print_r($document->fields());
        printf(PHP_EOL);
    } else {
        printf('Document %s does not exist!' . PHP_EOL, $snapshot->id());
    }
}

Recuperar todos os documentos em uma coleção

Também é possível recuperar todos os documentos em uma coleção. Para isso, basta omitir totalmente o filtro where():

Web
db.collection("cities").get().then(function(querySnapshot) {
    querySnapshot.forEach(function(doc) {
        // doc.data() is never undefined for query doc snapshots
        console.log(doc.id, " => ", doc.data());
    });
});
Swift
db.collection("cities").getDocuments() { (querySnapshot, err) in
    if let err = err {
        print("Error getting documents: \(err)")
    } else {
        for document in querySnapshot!.documents {
            print("\(document.documentID) => \(document.data())")
        }
    }
}
Objective-C
[[self.db collectionWithPath:@"cities"]
    getDocumentsWithCompletion:^(FIRQuerySnapshot *snapshot, NSError *error) {
      if (error != nil) {
        NSLog(@"Error getting documents: %@", error);
      } else {
        for (FIRDocumentSnapshot *document in snapshot.documents) {
          NSLog(@"%@ => %@", document.documentID, document.data);
        }
      }
    }];
  
Android
db.collection("cities")
        .get()
        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
            @Override
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                if (task.isSuccessful()) {
                    for (QueryDocumentSnapshot document : task.getResult()) {
                        Log.d(TAG, document.getId() + " => " + document.getData());
                    }
                } else {
                    Log.d(TAG, "Error getting documents: ", task.getException());
                }
            }
        });
Java
//asynchronously retrieve all documents
ApiFuture<QuerySnapshot> future = db.collection("cities").get();
// future.get() blocks on response
List<QueryDocumentSnapshot> documents = future.get().getDocuments();
for (QueryDocumentSnapshot document : documents) {
  System.out.println(document.getId() + " => " + document.toObject(City.class));
}
Python
docs = db.collection(u'cities').get()

for doc in docs:
    print(u'{} => {}'.format(doc.id, doc.to_dict()))
Node.js
var citiesRef = db.collection('cities');
var allCities = citiesRef.get()
    .then(snapshot => {
      snapshot.forEach(doc => {
        console.log(doc.id, '=>', doc.data());
      });
    })
    .catch(err => {
      console.log('Error getting documents', err);
    });
Go
fmt.Println("All cities:")
iter := client.Collection("cities").Documents(ctx)
for {
	doc, err := iter.Next()
	if err == iterator.Done {
		break
	}
	if err != nil {
		return err
	}
	fmt.Println(doc.Data())
}
PHP
$citiesRef = $db->collection('cities');
$documents = $citiesRef->documents();
foreach ($documents as $document) {
    if ($document->exists()) {
        printf('Document data for document %s:' . PHP_EOL, $document->id());
        print_r($document->fields());
        printf(PHP_EOL);
    } else {
        printf('Document %s does not exist!' . PHP_EOL, $snapshot->id());
    }
}

Listar as subcoleções de um documento

O método getCollections() das bibliotecas de cliente do servidor do Cloud Firestore lista todas as subcoleções de uma referência de documento.

Não é possível recuperar uma lista de coleções com as bibliotecas de cliente da Web/para dispositivos móveis. Procure nomes de coleções somente como parte de tarefas administrativas em ambientes de servidor confiáveis. Se você julgar que precisa desse recurso nas bibliotecas de clientes da Web/para dispositivos móveis, considere reestruturar seus dados para que os nomes de subcoleções sejam previsíveis.

Web
// Not available in the Web client library.
Swift
// Not available in the iOS client library.
Objective-C
// Not available in the Objective-C client library.
  
Android
// Not available in the Android client library.
Java
Iterable<CollectionReference> collections =
    db.collection("cities").document("SF").getCollections();

for (CollectionReference collRef : collections) {
  System.out.println("Found subcollection with id: " + collRef.getId());
}
Python
// Not available in the Python client library
Node.js
var sfRef = db.collection('cities').doc('SF');
sfRef.getCollections().then(collections => {
  collections.forEach(collection => {
    console.log('Found subcollection with id:', collection.id);
  });
});
Go
iter := client.Collection("cities").Doc("SF").Collections(ctx)
for {
	collRef, err := iter.Next()
	if err == iterator.Done {
		break
	}
	if err != nil {
		return err
	}
	fmt.Printf("Found collection with id: %s\n", collRef.ID)
}
PHP
$cityRef = $db->collection('cities')->document('SF');
$collections = $cityRef->collections();
foreach ($collections as $collection) {
    printf('Found subcollection with id: %s' . PHP_EOL, $collection->id());
}

Saiba mais sobre os diferentes tipos de consultas.

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