有两种方法可检索存储在 Firestore 中的数据。每种方法都可以用于文档、文档集合或查询结果:
- 调用一个方法来获取数据。
- 设置侦听器以接收数据更改事件。
当您设置监听器时,Firestore 会向监听器发送数据的初始快照,然后在文档每次发生更改时再发送一个快照。
示例数据
首先,请编写一些关于城市的数据,以便我们确定读回这些数据的不同方式:
Web
var citiesRef = db.collection("cities"); citiesRef.doc("SF").set({ name: "San Francisco", state: "CA", country: "USA", capital: false, population: 860000, regions: ["west_coast", "norcal"] }); citiesRef.doc("LA").set({ name: "Los Angeles", state: "CA", country: "USA", capital: false, population: 3900000, regions: ["west_coast", "socal"] }); citiesRef.doc("DC").set({ name: "Washington, D.C.", state: null, country: "USA", capital: true, population: 680000, regions: ["east_coast"] }); citiesRef.doc("TOK").set({ name: "Tokyo", state: null, country: "Japan", capital: true, population: 9000000, regions: ["kanto", "honshu"] }); citiesRef.doc("BJ").set({ name: "Beijing", state: null, country: "China", capital: true, population: 21500000, regions: ["jingjinji", "hebei"] });
Swift
let citiesRef = db.collection("cities") citiesRef.document("SF").setData([ "name": "San Francisco", "state": "CA", "country": "USA", "capital": false, "population": 860000, "regions": ["west_coast", "norcal"] ]) citiesRef.document("LA").setData([ "name": "Los Angeles", "state": "CA", "country": "USA", "capital": false, "population": 3900000, "regions": ["west_coast", "socal"] ]) citiesRef.document("DC").setData([ "name": "Washington D.C.", "country": "USA", "capital": true, "population": 680000, "regions": ["east_coast"] ]) citiesRef.document("TOK").setData([ "name": "Tokyo", "country": "Japan", "capital": true, "population": 9000000, "regions": ["kanto", "honshu"] ]) citiesRef.document("BJ").setData([ "name": "Beijing", "country": "China", "capital": true, "population": 21500000, "regions": ["jingjinji", "hebei"] ])
Objective-C
FIRCollectionReference *citiesRef = [self.db collectionWithPath:@"cities"]; [[citiesRef documentWithPath:@"SF"] setData:@{ @"name": @"San Francisco", @"state": @"CA", @"country": @"USA", @"capital": @(NO), @"population": @860000, @"regions": @[@"west_coast", @"norcal"] }]; [[citiesRef documentWithPath:@"LA"] setData:@{ @"name": @"Los Angeles", @"state": @"CA", @"country": @"USA", @"capital": @(NO), @"population": @3900000, @"regions": @[@"west_coast", @"socal"] }]; [[citiesRef documentWithPath:@"DC"] setData:@{ @"name": @"Washington D.C.", @"country": @"USA", @"capital": @(YES), @"population": @680000, @"regions": @[@"east_coast"] }]; [[citiesRef documentWithPath:@"TOK"] setData:@{ @"name": @"Tokyo", @"country": @"Japan", @"capital": @(YES), @"population": @9000000, @"regions": @[@"kanto", @"honshu"] }]; [[citiesRef documentWithPath:@"BJ"] setData:@{ @"name": @"Beijing", @"country": @"China", @"capital": @(YES), @"population": @21500000, @"regions": @[@"jingjinji", @"hebei"] }];
Java
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); data1.put("regions", Arrays.asList("west_coast", "norcal")); 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); data2.put("regions", Arrays.asList("west_coast", "socal")); 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); data3.put("regions", Arrays.asList("east_coast")); 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); data4.put("regions", Arrays.asList("kanto", "honshu")); 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); data5.put("regions", Arrays.asList("jingjinji", "hebei")); cities.document("BJ").set(data5);
Kotlin+KTX
Android
val cities = db.collection("cities") val data1 = hashMapOf( "name" to "San Francisco", "state" to "CA", "country" to "USA", "capital" to false, "population" to 860000, "regions" to listOf("west_coast", "norcal") ) cities.document("SF").set(data1) val data2 = hashMapOf( "name" to "Los Angeles", "state" to "CA", "country" to "USA", "capital" to false, "population" to 3900000, "regions" to listOf("west_coast", "socal") ) cities.document("LA").set(data2) val data3 = hashMapOf( "name" to "Washington D.C.", "state" to null, "country" to "USA", "capital" to true, "population" to 680000, "regions" to listOf("east_coast") ) cities.document("DC").set(data3) val data4 = hashMapOf( "name" to "Tokyo", "state" to null, "country" to "Japan", "capital" to true, "population" to 9000000, "regions" to listOf("kanto", "honshu") ) cities.document("TOK").set(data4) val data5 = hashMapOf( "name" to "Beijing", "state" to null, "country" to "China", "capital" to true, "population" to 21500000, "regions" to listOf("jingjinji", "hebei") ) 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, Arrays.asList("west_coast", "norcal")))); futures.add(cities.document("LA").set(new City("Los Angeles", "CA", "USA", false, 3900000L, Arrays.asList("west_coast", "socal")))); futures.add(cities.document("DC").set(new City("Washington D.C.", null, "USA", true, 680000L, Arrays.asList("east_coast")))); futures.add(cities.document("TOK").set(new City("Tokyo", null, "Japan", true, 9000000L, Arrays.asList("kanto", "honshu")))); futures.add(cities.document("BJ").set(new City("Beijing", null, "China", true, 21500000L, Arrays.asList("jingjinji", "hebei")))); // (optional) block on operation ApiFutures.allAsList(futures).get();
Python
class City(object): def __init__(self, name, state, country, capital=False, population=0, regions=[]): self.name = name self.state = state self.country = country self.capital = capital self.population = population self.regions = regions @staticmethod def from_dict(source): # ... def to_dict(self): # ... def __repr__(self): return( f'City(\ name={self.name}, \ country={self.country}, \ population={self.population}, \ capital={self.capital}, \ regions={self.regions}\ )' ) cities_ref = db.collection(u'cities') cities_ref.document(u'BJ').set( City(u'Beijing', None, u'China', True, 21500000, [u'hebei']).to_dict()) cities_ref.document(u'SF').set( City(u'San Francisco', u'CA', u'USA', False, 860000, [u'west_coast', u'norcal']).to_dict()) cities_ref.document(u'LA').set( City(u'Los Angeles', u'CA', u'USA', False, 3900000, [u'west_coast', u'socal']).to_dict()) cities_ref.document(u'DC').set( City(u'Washington D.C.', None, u'USA', True, 680000, [u'east_coast']).to_dict()) cities_ref.document(u'TOK').set( City(u'Tokyo', None, u'Japan', True, 9000000, [u'kanto', u'honshu']).to_dict())
C++
CollectionReference cities = db->Collection("cities"); cities.Document("SF").Set({ {"name", FieldValue::String("San Francisco")}, {"state", FieldValue::String("CA")}, {"country", FieldValue::String("USA")}, {"capital", FieldValue::Boolean(false)}, {"population", FieldValue::Integer(860000)}, {"regions", FieldValue::Array({FieldValue::String("west_coast"), FieldValue::String("norcal")})}, }); cities.Document("LA").Set({ {"name", FieldValue::String("Los Angeles")}, {"state", FieldValue::String("CA")}, {"country", FieldValue::String("USA")}, {"capital", FieldValue::Boolean(false)}, {"population", FieldValue::Integer(3900000)}, {"regions", FieldValue::Array({FieldValue::String("west_coast"), FieldValue::String("socal")})}, }); cities.Document("DC").Set({ {"name", FieldValue::String("Washington D.C.")}, {"state", FieldValue::Null()}, {"country", FieldValue::String("USA")}, {"capital", FieldValue::Boolean(true)}, {"population", FieldValue::Integer(680000)}, {"regions", FieldValue::Array({FieldValue::String("east_coast")})}, }); cities.Document("TOK").Set({ {"name", FieldValue::String("Tokyo")}, {"state", FieldValue::Null()}, {"country", FieldValue::String("Japan")}, {"capital", FieldValue::Boolean(true)}, {"population", FieldValue::Integer(9000000)}, {"regions", FieldValue::Array({FieldValue::String("kanto"), FieldValue::String("honshu")})}, }); cities.Document("BJ").Set({ {"name", FieldValue::String("Beijing")}, {"state", FieldValue::Null()}, {"country", FieldValue::String("China")}, {"capital", FieldValue::Boolean(true)}, {"population", FieldValue::Integer(21500000)}, {"regions", FieldValue::Array({FieldValue::String("jingjinji"), FieldValue::String("hebei")})}, });
Node.js
const citiesRef = db.collection('cities'); await citiesRef.doc('SF').set({ name: 'San Francisco', state: 'CA', country: 'USA', capital: false, population: 860000 }); await citiesRef.doc('LA').set({ name: 'Los Angeles', state: 'CA', country: 'USA', capital: false, population: 3900000 }); await citiesRef.doc('DC').set({ name: 'Washington, D.C.', state: null, country: 'USA', capital: true, population: 680000 }); await citiesRef.doc('TOK').set({ name: 'Tokyo', state: null, country: 'Japan', capital: true, population: 9000000 }); await 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: true, 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);
Unity
CollectionReference citiesRef = db.Collection("cities"); citiesRef.Document("SF").SetAsync(new Dictionary<string, object>(){ { "Name", "San Francisco" }, { "State", "CA" }, { "Country", "USA" }, { "Capital", false }, { "Population", 860000 } }).ContinueWithOnMainThread(task => citiesRef.Document("LA").SetAsync(new Dictionary<string, object>(){ { "Name", "Los Angeles" }, { "State", "CA" }, { "Country", "USA" }, { "Capital", false }, { "Population", 3900000 } }) ).ContinueWithOnMainThread(task => citiesRef.Document("DC").SetAsync(new Dictionary<string, object>(){ { "Name", "Washington D.C." }, { "State", null }, { "Country", "USA" }, { "Capital", true }, { "Population", 680000 } }) ).ContinueWithOnMainThread(task => citiesRef.Document("TOK").SetAsync(new Dictionary<string, object>(){ { "Name", "Tokyo" }, { "State", null }, { "Country", "Japan" }, { "Capital", true }, { "Population", 9000000 } }) ).ContinueWithOnMainThread(task => citiesRef.Document("BJ").SetAsync(new Dictionary<string, object>(){ { "Name", "Beijing" }, { "State", null }, { "Country", "China" }, { "Capital", true }, { "Population", 21500000 } }) );
C#
CollectionReference citiesRef = db.Collection("cities"); await citiesRef.Document("SF").SetAsync(new Dictionary<string, object>(){ { "Name", "San Francisco" }, { "State", "CA" }, { "Country", "USA" }, { "Capital", false }, { "Population", 860000 } }); await citiesRef.Document("LA").SetAsync(new Dictionary<string, object>(){ { "Name", "Los Angeles" }, { "State", "CA" }, { "Country", "USA" }, { "Capital", false }, { "Population", 3900000 } }); await citiesRef.Document("DC").SetAsync(new Dictionary<string, object>(){ { "Name", "Washington D.C." }, { "State", null }, { "Country", "USA" }, { "Capital", true }, { "Population", 680000 } }); await citiesRef.Document("TOK").SetAsync(new Dictionary<string, object>(){ { "Name", "Tokyo" }, { "State", null }, { "Country", "Japan" }, { "Capital", true }, { "Population", 9000000 } }); await citiesRef.Document("BJ").SetAsync(new Dictionary<string, object>(){ { "Name", "Beijing" }, { "State", null }, { "Country", "China" }, { "Capital", true }, { "Population", 21500000 } }); Console.WriteLine("Added example cities data to the cities collection.");
Ruby
cities_ref = firestore.col collection_path cities_ref.doc("SF").set( name: "San Francisco", state: "CA", country: "USA", capital: false, population: 860_000 ) cities_ref.doc("LA").set( name: "Los Angeles", state: "CA", country: "USA", capital: false, population: 3_900_000 ) cities_ref.doc("DC").set( name: "Washington D.C.", state: nil, country: "USA", capital: true, population: 680_000 ) cities_ref.doc("TOK").set( name: "Tokyo", state: nil, country: "Japan", capital: true, population: 9_000_000 ) cities_ref.doc("BJ").set( name: "Beijing", state: nil, country: "China", capital: true, population: 21_500_000 )
获取文档
以下示例展示了如何使用 get()
检索单个文档的内容:
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"); } }];
Java
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()); } } });
Kotlin+KTX
Android
val docRef = db.collection("cities").document("SF") docRef.get() .addOnSuccessListener { document -> if (document != null) { Log.d(TAG, "DocumentSnapshot data: ${document.data}") } else { Log.d(TAG, "No such document") } } .addOnFailureListener { exception -> Log.d(TAG, "get failed with ", exception) }
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') doc = doc_ref.get() if doc.exists: print(f'Document data: {doc.to_dict()}') else: print(u'No such document!')
C++
DocumentReference doc_ref = db->Collection("cities").Document("SF"); doc_ref.Get().OnCompletion([](const Future<DocumentSnapshot>& future) { if (future.error() == Error::kErrorOk) { const DocumentSnapshot& document = *future.result(); if (document.exists()) { std::cout << "DocumentSnapshot id: " << document.id() << '\n'; } else { std::cout << "no such document\n"; } } else { std::cout << "Get failed with: " << future.error_message() << '\n'; } });
Node.js
const cityRef = db.collection('cities').doc('SF'); const doc = await cityRef.get(); if (!doc.exists) { console.log('No such document!'); } else { console.log('Document data:', doc.data()); }
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->data()); } else { printf('Document %s does not exist!' . PHP_EOL, $snapshot->id()); }
Unity
DocumentReference docRef = db.Collection("cities").Document("SF"); docRef.GetSnapshotAsync().ContinueWithOnMainThread(task => { DocumentSnapshot snapshot = task.Result; if (snapshot.Exists) { Debug.Log(String.Format("Document data for {0} document:", snapshot.Id)); Dictionary<string, object> city = snapshot.ToDictionary(); foreach (KeyValuePair<string, object> pair in city) { Debug.Log(String.Format("{0}: {1}", pair.Key, pair.Value)); } } else { Debug.Log(String.Format("Document {0} does not exist!", snapshot.Id)); } });
C#
DocumentReference docRef = db.Collection("cities").Document("SF"); DocumentSnapshot snapshot = await docRef.GetSnapshotAsync(); if (snapshot.Exists) { Console.WriteLine("Document data for {0} document:", snapshot.Id); Dictionary<string, object> city = snapshot.ToDictionary(); foreach (KeyValuePair<string, object> pair in city) { Console.WriteLine("{0}: {1}", pair.Key, pair.Value); } } else { Console.WriteLine("Document {0} does not exist!", snapshot.Id); }
Ruby
doc_ref = firestore.doc "#{collection_path}/SF" snapshot = doc_ref.get if snapshot.exists? puts "#{snapshot.document_id} data: #{snapshot.data}." else puts "Document #{snapshot.document_id} does not exist!" end
Source 选项
对于提供离线支持的平台,您可以设置 source
选项以控制 get
调用如何使用离线缓存。
默认情况下,get
调用会尝试从您的数据库中提取最新的文档快照。在提供离线支持的平台上,如果网络不可用或者请求超时,客户端库将使用离线缓存。
您可以在 get()
调用中指定 source
选项,以更改默认行为。您可以只从数据库中提取并忽略离线缓存,或者只从离线缓存中提取。例如:
Web
var docRef = db.collection("cities").doc("SF"); // Valid options for source are 'server', 'cache', or // 'default'. See https://firebase.google.com/docs/reference/js/firebase.firestore.GetOptions // for more information. var getOptions = { source: 'cache' }; // Get a document, forcing the SDK to fetch from the offline cache. docRef.get(getOptions).then(function(doc) { // Document was found in the cache. If no cached document exists, // an error will be returned to the 'catch' block below. console.log("Cached document data:", doc.data()); }).catch(function(error) { console.log("Error getting cached document:", error); });
Swift
let docRef = db.collection("cities").document("SF") // Force the SDK to fetch the document from the cache. Could also specify // FirestoreSource.server or FirestoreSource.default. docRef.getDocument(source: .cache) { (document, error) in if let document = document { let dataDescription = document.data().map(String.init(describing:)) ?? "nil" print("Cached document data: \(dataDescription)") } else { print("Document does not exist in cache") } }
Objective-C
FIRDocumentReference *docRef = [[self.db collectionWithPath:@"cities"] documentWithPath:@"SF"]; // Force the SDK to fetch the document from the cache. Could also specify // FIRFirestoreSourceServer or FIRFirestoreSourceDefault. [docRef getDocumentWithSource:FIRFirestoreSourceCache completion:^(FIRDocumentSnapshot *snapshot, NSError *error) { if (snapshot != NULL) { // The document data was found in the cache. NSLog(@"Cached document data: %@", snapshot.data); } else { // The document data was not found in the cache. NSLog(@"Document does not exist in cache: %@", error); } }];
Java
Android
DocumentReference docRef = db.collection("cities").document("SF"); // Source can be CACHE, SERVER, or DEFAULT. Source source = Source.CACHE; // Get the document, forcing the SDK to use the offline cache docRef.get(source).addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() { @Override public void onComplete(@NonNull Task<DocumentSnapshot> task) { if (task.isSuccessful()) { // Document found in the offline cache DocumentSnapshot document = task.getResult(); Log.d(TAG, "Cached document data: " + document.getData()); } else { Log.d(TAG, "Cached get failed: ", task.getException()); } } });
Kotlin+KTX
Android
val docRef = db.collection("cities").document("SF") // Source can be CACHE, SERVER, or DEFAULT. val source = Source.CACHE // Get the document, forcing the SDK to use the offline cache docRef.get(source).addOnCompleteListener { task -> if (task.isSuccessful) { // Document found in the offline cache val document = task.result Log.d(TAG, "Cached document data: ${document?.data}") } else { Log.d(TAG, "Cached get failed: ", task.exception) } }
Java
在 Java SDK 中不受支持。
Python
在 Python SDK 中不受支持。
C++
DocumentReference doc_ref = db->Collection("cities").Document("SF"); Source source = Source::kCache; doc_ref.Get(source).OnCompletion([](const Future<DocumentSnapshot>& future) { if (future.error() == Error::kErrorOk) { const DocumentSnapshot& document = *future.result(); if (document.exists()) { std::cout << "Cached document id: " << document.id() << '\n'; } else { } } else { std::cout << "Cached get failed: " << future.error_message() << '\n'; } });
Node.js
在 Node.js SDK 中不受支持。
Go
在 Go SDK 中不受支持。
PHP
在 PHP SDK 中不受支持。
Unity
在 Unity SDK 中不受支持。
C#
在 C# SDK 中不受支持。
Ruby
在 Ruby SDK 中不受支持。
自定义对象
上例检索了文档的内容以用作地图,但在某些编程语言中,使用自定义对象类型通常更为方便。在添加数据中,您定义了一个用于定义每个城市的 City
类。您可以将文档重新变回 City
对象:
网页
要使用自定义对象,您必须为您的类定义 FirestoreDataConverter 函数。例如:
class City { constructor (name, state, country ) { this.name = name; this.state = state; this.country = country; } toString() { return this.name + ', ' + this.state + ', ' + this.country; } } // Firestore data converter var cityConverter = { toFirestore: function(city) { return { name: city.name, state: city.state, country: city.country }; }, fromFirestore: function(snapshot, options){ const data = snapshot.data(options); return new City(data.name, data.state, data.country); } };通过读取操作调用数据转换器。转换后,您可以访问自定义对象方法:
db.collection("cities").doc("LA") .withConverter(cityConverter) .get().then(function(doc) { if (doc.exists){ // Convert to City object var city = doc.data(); // Use a City instance method console.log(city.toString()); } else { console.log("No such document!"); }}).catch(function(error) { console.log("Error getting document:", error); });
Swift
要在 Swift 中支持自动类型序列化,您的类型必须符合 Codable 协议,并且您必须将 pod 'FirebaseFirestoreSwift'
添加为项目的依赖项。
let docRef = db.collection("cities").document("BJ") docRef.getDocument { (document, error) in // Construct a Result type to encapsulate deserialization errors or // successful deserialization. Note that if there is no error thrown // the value may still be `nil`, indicating a successful deserialization // of a value that does not exist. // // There are thus three cases to handle, which Swift lets us describe // nicely with built-in Result types: // // Result // /\ // Error Optional<City> // /\ // Nil City let result = Result { try document?.data(as: City.self) } switch result { case .success(let city): if let city = city { // A `City` value was successfully initialized from the DocumentSnapshot. print("City: \(city)") } else { // A nil value was successfully initialized from the DocumentSnapshot, // or the DocumentSnapshot was nil. print("Document does not exist") } case .failure(let error): // A `City` value could not be initialized from the DocumentSnapshot. print("Error decoding city: \(error)") } }
Objective-C
在 Objective-C 中,您必须手动执行此操作。
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"); } }];
Java
Android
重要提示:每个自定义类都必须有一个不接受任何参数的公共构造函数。此外,类必须为每个属性包含一个公共 getter。
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); } });
Kotlin+KTX
Android
val docRef = db.collection("cities").document("BJ") docRef.get().addOnSuccessListener { documentSnapshot -> val city = documentSnapshot.toObject<City>() }
Java
每个自定义类都必须有一个不接受任何参数的公共构造函数。此外,类必须为每个属性包含一个公共 getter。
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)
C++
// This is not yet supported.
Node.js
Node.js 使用 JavaScript 对象。
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
不适用于 PHP。
Unity
DocumentReference docRef = db.Collection("cities").Document("BJ"); docRef.GetSnapshotAsync().ContinueWith((task) => { var snapshot = task.Result; if (snapshot.Exists) { Debug.Log(String.Format("Document data for {0} document:", snapshot.Id)); City city = snapshot.ConvertTo<City>(); Debug.Log(String.Format("Name: {0}", city.Name)); Debug.Log(String.Format("State: {0}", city.State)); Debug.Log(String.Format("Country: {0}", city.Country)); Debug.Log(String.Format("Capital: {0}", city.Capital)); Debug.Log(String.Format("Population: {0}", city.Population)); } else { Debug.Log(String.Format("Document {0} does not exist!", snapshot.Id)); } });
C#
DocumentReference docRef = db.Collection("cities").Document("BJ"); DocumentSnapshot snapshot = await docRef.GetSnapshotAsync(); if (snapshot.Exists) { Console.WriteLine("Document data for {0} document:", snapshot.Id); City city = snapshot.ConvertTo<City>(); Console.WriteLine("Name: {0}", city.Name); Console.WriteLine("State: {0}", city.State); Console.WriteLine("Country: {0}", city.Country); Console.WriteLine("Capital: {0}", city.Capital); Console.WriteLine("Population: {0}", city.Population); } else { Console.WriteLine("Document {0} does not exist!", snapshot.Id); }
Ruby
不适用于 Ruby。
从集合中获取多个文档
您还可以查询某个集合中的文档,从而使用一个请求检索多个文档。例如,您可以使用 where()
来查询满足特定条件的所有文档,然后使用 get()
检索结果:
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); } } }];
Java
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()); } } });
Kotlin+KTX
Android
db.collection("cities") .whereEqualTo("capital", true) .get() .addOnSuccessListener { documents -> for (document in documents) { Log.d(TAG, "${document.id} => ${document.data}") } } .addOnFailureListener { exception -> Log.w(TAG, "Error getting documents: ", exception) }
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
# Note: Use of CollectionRef stream() is prefered to get() docs = db.collection(u'cities').where(u'capital', u'==', True).stream() for doc in docs: print(f'{doc.id} => {doc.to_dict()}')
C++
db->Collection("cities") .WhereEqualTo("capital", FieldValue::Boolean(true)) .Get() .OnCompletion([](const Future<QuerySnapshot>& future) { if (future.error() == Error::kErrorOk) { for (const DocumentSnapshot& document : future.result()->documents()) { std::cout << document << '\n'; } } else { std::cout << "Error getting documents: " << future.error_message() << '\n'; } });
Node.js
const citiesRef = db.collection('cities'); const snapshot = await citiesRef.where('capital', '==', true).get(); if (snapshot.empty) { console.log('No matching documents.'); return; } snapshot.forEach(doc => { console.log(doc.id, '=>', doc.data()); });
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->data()); printf(PHP_EOL); } else { printf('Document %s does not exist!' . PHP_EOL, $snapshot->id()); } }
Unity
Query capitalQuery = db.Collection("cities").WhereEqualTo("Capital", true); capitalQuery.GetSnapshotAsync().ContinueWithOnMainThread(task => { QuerySnapshot capitalQuerySnapshot = task.Result; foreach (DocumentSnapshot documentSnapshot in capitalQuerySnapshot.Documents) { Debug.Log(String.Format("Document data for {0} document:", documentSnapshot.Id)); Dictionary<string, object> city = documentSnapshot.ToDictionary(); foreach (KeyValuePair<string, object> pair in city) { Debug.Log(String.Format("{0}: {1}", pair.Key, pair.Value)); } // Newline to separate entries Debug.Log(""); }; });
C#
Query capitalQuery = db.Collection("cities").WhereEqualTo("Capital", true); QuerySnapshot capitalQuerySnapshot = await capitalQuery.GetSnapshotAsync(); foreach (DocumentSnapshot documentSnapshot in capitalQuerySnapshot.Documents) { Console.WriteLine("Document data for {0} document:", documentSnapshot.Id); Dictionary<string, object> city = documentSnapshot.ToDictionary(); foreach (KeyValuePair<string, object> pair in city) { Console.WriteLine("{0}: {1}", pair.Key, pair.Value); } Console.WriteLine(""); }
Ruby
cities_ref = firestore.col collection_path query = cities_ref.where "capital", "=", true query.get do |city| puts "#{city.document_id} data: #{city.data}." end
默认情况下,Firestore 按文档 ID 以升序检索所有符合查询的文档,但您可以对返回的数据进行排序和限制其数量。
获取集合中的所有文档
此外,您可以通过完全省略 where()
过滤条件来检索集合中的所有文档:
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); } } }];
Java
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()); } } });
Kotlin+KTX
Android
db.collection("cities") .get() .addOnSuccessListener { result -> for (document in result) { Log.d(TAG, "${document.id} => ${document.data}") } } .addOnFailureListener { exception -> Log.d(TAG, "Error getting documents: ", exception) }
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').stream() for doc in docs: print(f'{doc.id} => {doc.to_dict()}')
C++
db->Collection("cities").Get().OnCompletion( [](const Future<QuerySnapshot>& future) { if (future.error() == Error::kErrorOk) { for (const DocumentSnapshot& document : future.result()->documents()) { std::cout << document << '\n'; } } else { std::cout << "Error getting documents: " << future.error_message() << '\n'; } });
Node.js
const citiesRef = db.collection('cities'); const snapshot = await citiesRef.get(); snapshot.forEach(doc => { console.log(doc.id, '=>', doc.data()); });
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->data()); printf(PHP_EOL); } else { printf('Document %s does not exist!' . PHP_EOL, $snapshot->id()); } }
Unity
Query allCitiesQuery = db.Collection("cities"); allCitiesQuery.GetSnapshotAsync().ContinueWithOnMainThread(task => { QuerySnapshot allCitiesQuerySnapshot = task.Result; foreach (DocumentSnapshot documentSnapshot in allCitiesQuerySnapshot.Documents) { Debug.Log(String.Format("Document data for {0} document:", documentSnapshot.Id)); Dictionary<string, object> city = documentSnapshot.ToDictionary(); foreach (KeyValuePair<string, object> pair in city) { Debug.Log(String.Format("{0}: {1}", pair.Key, pair.Value)); } // Newline to separate entries Debug.Log(""); } }); Test
C#
Query allCitiesQuery = db.Collection("cities"); QuerySnapshot allCitiesQuerySnapshot = await allCitiesQuery.GetSnapshotAsync(); foreach (DocumentSnapshot documentSnapshot in allCitiesQuerySnapshot.Documents) { Console.WriteLine("Document data for {0} document:", documentSnapshot.Id); Dictionary<string, object> city = documentSnapshot.ToDictionary(); foreach (KeyValuePair<string, object> pair in city) { Console.WriteLine("{0}: {1}", pair.Key, pair.Value); } Console.WriteLine(""); }
Ruby
cities_ref = firestore.col collection_path cities_ref.get do |city| puts "#{city.document_id} data: #{city.data}." end
从集合组中获取多个文档
集合组由具有相同 ID 的所有集合组成。例如,如果您的 cities
集合中的每个文档都有一个名为 landmarks
的子集合,则所有 landmarks
子集合都属于同一个集合组。默认情况下,查询从数据库的单个集合中检索结果。您可以使用集合组查询从集合组中检索结果,而不是从单个集合中检索结果。
列出文档的子集合
Firestore 服务器客户端库的 getCollections()
方法列出了文档引用的所有子集合。
无法通过移动/Web 客户端库检索集合的列表。只有在可信的服务器环境中执行管理性任务时,您才能查询集合名称。如果您发现需要在移动/Web 客户端库中使用此功能,建议您重新设计数据的结构,以便子集合名称可以预测。
Web
在 Web 客户端库中不适用。
Swift
在 iOS 客户端库中不适用。
Objective-C
在 Objective-C 客户端库中不适用。
Java
Android
在 Android 客户端库中不适用。
Kotlin+KTX
Android
在 Android 客户端库中不适用。
Java
Iterable<CollectionReference> collections = db.collection("cities").document("SF").listCollections(); for (CollectionReference collRef : collections) { System.out.println("Found subcollection with id: " + collRef.getId()); }
Python
collections = db.collection('cities').document('SF').collections() for collection in collections: for doc in collection.stream(): print(f'{doc.id} => {doc.to_dict()}')
C++
在 C++ 客户端库中不适用。
Node.js
const sfRef = db.collection('cities').doc('SF'); const collections = await sfRef.listCollections(); 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()); }
Unity
// This is not yet supported in the Unity SDK.
C#
DocumentReference cityRef = db.Collection("cities").Document("SF"); IAsyncEnumerable<CollectionReference> subcollections = cityRef.ListCollectionsAsync(); IAsyncEnumerator<CollectionReference> subcollectionsEnumerator = subcollections.GetAsyncEnumerator(default); while (await subcollectionsEnumerator.MoveNextAsync()) { CollectionReference subcollectionRef = subcollectionsEnumerator.Current; Console.WriteLine("Found subcollection with ID: {0}", subcollectionRef.Id); }
Ruby
city_ref = firestore.doc "#{collection_path}/SF" city_ref.cols do |col| puts col.collection_id end
详细了解各种不同的查询类型。