有兩種方法可以檢索存儲在 Cloud Firestore 中的數據。這些方法中的任何一種都可以用於文檔、文檔集合或查詢結果：
- 調用方法來獲取數據。
- 設置偵聽器以接收數據更改事件。
設置偵聽器時，Cloud Firestore 會向您的偵聽器發送數據的初始快照，然後在每次文檔更改時發送另一個快照。
示例數據
首先，寫一些關於城市的數據，這樣我們就可以看看不同的方式來讀回它：
Web version 9
import { collection, doc, setDoc } from "firebase/firestore";
const citiesRef = collection(db, "cities");
await setDoc(doc(citiesRef, "SF"), {
name: "San Francisco", state: "CA", country: "USA",
capital: false, population: 860000,
regions: ["west_coast", "norcal"] });
await setDoc(doc(citiesRef, "LA"), {
name: "Los Angeles", state: "CA", country: "USA",
capital: false, population: 3900000,
regions: ["west_coast", "socal"] });
await setDoc(doc(citiesRef, "DC"), {
name: "Washington, D.C.", state: null, country: "USA",
capital: true, population: 680000,
regions: ["east_coast"] });
await setDoc(doc(citiesRef, "TOK"), {
name: "Tokyo", state: null, country: "Japan",
capital: true, population: 9000000,
regions: ["kanto", "honshu"] });
await setDoc(doc(citiesRef, "BJ"), {
name: "Beijing", state: null, country: "China",
capital: true, population: 21500000,
regions: ["jingjinji", "hebei"] });Web version 8
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"] });迅速
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
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
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)Dart
final cities = db.collection("cities");
final data1 = <String, dynamic>{
"name": "San Francisco",
"state": "CA",
"country": "USA",
"capital": false,
"population": 860000,
"regions": ["west_coast", "norcal"]
};
cities.doc("SF").set(data1);
final data2 = <String, dynamic>{
"name": "Los Angeles",
"state": "CA",
"country": "USA",
"capital": false,
"population": 3900000,
"regions": ["west_coast", "socal"],
};
cities.doc("LA").set(data2);
final data3 = <String, dynamic>{
"name": "Washington D.C.",
"state": null,
"country": "USA",
"capital": true,
"population": 680000,
"regions": ["east_coast"]
};
cities.doc("DC").set(data3);
final data4 = <String, dynamic>{
"name": "Tokyo",
"state": null,
"country": "Japan",
"capital": true,
"population": 9000000,
"regions": ["kanto", "honshu"]
};
cities.doc("TOK").set(data4);
final data5 = <String, dynamic>{
"name": "Beijing",
"state": null,
"country": "China",
"capital": true,
"population": 21500000,
"regions": ["jingjinji", "hebei"],
};
cities.doc("BJ").set(data5);爪哇
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())Python
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")})},
});節點.js
去
PHP
$citiesRef = $db->collection('samples/php/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);統一
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.");紅寶石
獲取文件
以下示例顯示如何使用get()檢索單個文檔的內容：
Web version 9
import { doc, getDoc } from "firebase/firestore";
const docRef = doc(db, "cities", "SF");
const docSnap = await getDoc(docRef);
if (docSnap.exists()) {
console.log("Document data:", docSnap.data());
} else {
// doc.data() will be undefined in this case
console.log("No such document!");
}Web version 8
var docRef = db.collection("cities").doc("SF");
docRef.get().then((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((error) => {
console.log("Error getting document:", error);
});迅速
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
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
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)
}Dart
final docRef = db.collection("cities").doc("SF");
docRef.get().then(
(DocumentSnapshot doc) {
final data = doc.data() as Map<String, dynamic>;
// ...
},
onError: (e) => print("Error getting document: $e"),
);爪哇
Python
Python
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() << std::endl;
} else {
std::cout << "no such document" << std::endl;
}
} else {
std::cout << "Get failed with: " << future.error_message() << std::endl;
}
});節點.js
去
PHP
$docRef = $db->collection('samples/php/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());
}統一
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);
}紅寶石
源選項
對於具有離線支持的平台，您可以設置source選項來控制get調用如何使用離線緩存。
默認情況下， get調用將嘗試從您的數據庫中獲取最新的文檔快照。在支持離線的平台上，如果網絡不可用或請求超時，客戶端庫將使用離線緩存。
您可以在get()調用中指定source選項以更改默認行為。您可以僅從數據庫中獲取而忽略離線緩存，也可以僅從離線緩存中獲取。例如：
Web version 9
import { doc, getDocFromCache } from "firebase/firestore";
const docRef = doc(db, "cities", "SF");
// Get a document, forcing the SDK to fetch from the offline cache.
try {
const doc = await getDocFromCache(docRef);
// 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 (e) {
console.log("Error getting cached document:", e);
}Web version 8
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((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((error) => {
console.log("Error getting cached document:", error);
});迅速
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
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
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)
}
}Dart
final docRef = db.collection("cities").doc("SF");
// Source can be CACHE, SERVER, or DEFAULT.
const source = Source.cache;
docRef.get(const GetOptions(source: source)).then(
(res) => print("Successfully completed"),
onError: (e) => print("Error completing: $e"),
);爪哇
Java SDK 不支持。
Python
Python SDK 不支持。
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() << std::endl;
} else {
}
} else {
std::cout << "Cached get failed: " << future.error_message() << std::endl;
}
});節點.js
Node.js SDK 不支持。
去
Go SDK 不支持。
PHP
PHP SDK 不支持。
統一
Unity SDK 不支持。
C＃
C# SDK 不支持。
紅寶石
Ruby SDK 不支持。
自定義對象
前面的示例將文檔的內容作為地圖檢索，但在某些語言中，使用自定義對像類型通常更方便。在Add Data中，您定義了用於定義每個城市的City類。您可以將文檔轉回City對象：
要使用自定義對象，您必須為您的類定義FirestoreDataConverter函數。例如：
Web version 9
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
const cityConverter = {
toFirestore: (city) => {
return {
name: city.name,
state: city.state,
country: city.country
};
},
fromFirestore: (snapshot, options) => {
const data = snapshot.data(options);
return new City(data.name, data.state, data.country);
}
};要使用自定義對象，您必須為您的類定義FirestoreDataConverter函數。例如：
Web version 8
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);
}
};使用您的讀取操作調用您的數據轉換器。轉換後，您可以訪問自定義對象方法：
Web version 9
import { doc, getDoc} from "firebase/firestore";
const ref = doc(db, "cities", "LA").withConverter(cityConverter);
const docSnap = await getDoc(ref);
if (docSnap.exists()) {
// Convert to City object
const city = docSnap.data();
// Use a City instance method
console.log(city.toString());
} else {
console.log("No such document!");
}使用您的讀取操作調用您的數據轉換器。轉換後，您可以訪問自定義對象方法：
Web version 8
db.collection("cities").doc("LA")
.withConverter(cityConverter)
.get().then((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((error) => {
console.log("Error getting document:", error);
});迅速
注意：此產品不適用於 watchOS 和 App Clip 目標。
要在 Swift 中支持自動類型序列化，您的類型必須符合Codable 協議，並且您必須包含pod 'FirebaseFirestoreSwift'作為項目的依賴項。
let docRef = db.collection("cities").document("BJ")
docRef.getDocument(as: City.self) { result in
// The Result type encapsulates deserialization errors or
// successful deserialization, and can be handled as follows:
//
// Result
// /\
// Error City
switch result {
case .success(let city):
// A `City` value was successfully initialized from the DocumentSnapshot.
print("City: \(city)")
case .failure(let error):
// A `City` value could not be initialized from the DocumentSnapshot.
print("Error decoding city: \(error)")
}
}Objective-C
注意：此產品不適用於 watchOS 和 App Clip 目標。
在 Objective-C 中，您必須手動執行此操作。
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
重要提示：每個自定義類都必須有一個不帶參數的公共構造函數。此外，該類必須為每個屬性包含一個公共 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
val docRef = db.collection("cities").document("BJ")
docRef.get().addOnSuccessListener { documentSnapshot ->
val city = documentSnapshot.toObject<City>()
}Dart
要使用自定義對象，您必須為您的類定義 Firestore 數據轉換函數。例如：
class City {
final String? name;
final String? state;
final String? country;
final bool? capital;
final int? population;
final List<String>? regions;
City({
this.name,
this.state,
this.country,
this.capital,
this.population,
this.regions,
});
factory City.fromFirestore(
DocumentSnapshot<Map<String, dynamic>> snapshot,
SnapshotOptions? options,
) {
final data = snapshot.data();
return City(
name: data?['name'],
state: data?['state'],
country: data?['country'],
capital: data?['capital'],
population: data?['population'],
regions:
data?['regions'] is Iterable ? List.from(data?['regions']) : null,
);
}
Map<String, dynamic> toFirestore() {
return {
if (name != null) "name": name,
if (state != null) "state": state,
if (country != null) "country": country,
if (capital != null) "capital": capital,
if (population != null) "population": population,
if (regions != null) "regions": regions,
};
}
}然後，使用您的數據轉換函數創建文檔參考。您使用此引用執行的任何讀取操作都將返回您的自定義類的實例：
final ref = db.collection("cities").doc("LA").withConverter(
fromFirestore: City.fromFirestore,
toFirestore: (City city, _) => city.toFirestore(),
);
final docSnap = await ref.get();
final city = docSnap.data(); // Convert to City object
if (city != null) {
print(city);
} else {
print("No such document.");
}爪哇
每個自定義類都必須有一個不帶參數的公共構造函數。此外，該類必須為每個屬性包含一個公共 getter。
Python
Python
C++
// This is not yet supported.
節點.js
Node.js 使用 JavaScript 對象。
去
PHP
不適用於 PHP。
統一
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);
}紅寶石
不適用於 Ruby。
從集合中獲取多個文檔
您還可以通過查詢集合中的文檔，用一個請求檢索多個文檔。例如，您可以使用where()查詢所有滿足特定條件的文檔，然後使用get()檢索結果：
Web version 9
import { collection, query, where, getDocs } from "firebase/firestore";
const q = query(collection(db, "cities"), where("capital", "==", true));
const querySnapshot = await getDocs(q);
querySnapshot.forEach((doc) => {
// doc.data() is never undefined for query doc snapshots
console.log(doc.id, " => ", doc.data());
});Web version 8
db.collection("cities").where("capital", "==", true)
.get()
.then((querySnapshot) => {
querySnapshot.forEach((doc) => {
// doc.data() is never undefined for query doc snapshots
console.log(doc.id, " => ", doc.data());
});
})
.catch((error) => {
console.log("Error getting documents: ", error);
});迅速
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
注意：此產品不適用於 watchOS 和 App Clip 目標。
[[[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
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
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)
}Dart
db.collection("cities").where("capital", isEqualTo: true).get().then(
(res) => print("Successfully completed"),
onError: (e) => print("Error completing: $e"),
);爪哇
Python
Python
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 << std::endl;
}
} else {
std::cout << "Error getting documents: " << future.error_message()
<< std::endl;
}
});節點.js
去
PHP
$citiesRef = $db->collection('samples/php/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, $document->id());
}
}統一
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("");
}紅寶石
默認情況下，Cloud Firestore 按文檔 ID 升序檢索滿足查詢的所有文檔，但您可以對返回的數據進行排序和限制。
獲取集合中的所有文檔
此外，您可以通過完全省略where()過濾器來檢索集合中的所有文檔：
Web version 9
import { collection, getDocs } from "firebase/firestore";
const querySnapshot = await getDocs(collection(db, "cities"));
querySnapshot.forEach((doc) => {
// doc.data() is never undefined for query doc snapshots
console.log(doc.id, " => ", doc.data());
});Web version 8
db.collection("cities").get().then((querySnapshot) => {
querySnapshot.forEach((doc) => {
// doc.data() is never undefined for query doc snapshots
console.log(doc.id, " => ", doc.data());
});
});迅速
注意：此產品不適用於 watchOS 和 App Clip 目標。
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
注意：此產品不適用於 watchOS 和 App Clip 目標。
[[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
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
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)
}Dart
db.collection("cities").get().then(
(res) => print("Successfully completed"),
onError: (e) => print("Error completing: $e"),
);爪哇
Python
Python
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 << std::endl;
}
} else {
std::cout << "Error getting documents: " << future.error_message()
<< std::endl;
}
});節點.js
去
PHP
$citiesRef = $db->collection('samples/php/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, $document->id());
}
}統一
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("");
}
});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("");
}紅寶石
從集合組中獲取多個文檔
集合組由具有相同 ID 的所有集合組成。例如，如果您的cities集合中的每個文檔都有一個名為landmarks的子集合，那麼所有landmarks子集合都屬於同一個集合組。默認情況下，查詢從數據庫中的單個集合中檢索結果。使用集合組查詢從集合組而不是單個集合中檢索結果。
列出文檔的子集合
Cloud Firestore 服務器客戶端庫的listCollections()方法列出了文檔引用的所有子集合。
使用移動/Web 客戶端庫無法檢索集合列表。您應該只在受信任的服務器環境中將集合名稱作為管理任務的一部分進行查找。如果您發現在移動/Web 客戶端庫中需要此功能，請考慮重構您的數據，以便子集合名稱是可預測的。
網絡
在 Web 客戶端庫中不可用。
迅速
在 Swift 客戶端庫中不可用。
Objective-C
在 Objective-C 客戶端庫中不可用。
Java
在 Android 客戶端庫中不可用。
Kotlin+KTX
在 Android 客戶端庫中不可用。
Dart
在 Flutter 客戶端庫中不可用。
爪哇
Python
Python
C++
在 C++ 客戶端庫中不可用。
節點.js
去
PHP
$cityRef = $db->collection('samples/php/cities')->document('SF');
$collections = $cityRef->collections();
foreach ($collections as $collection) {
printf('Found subcollection with id: %s' . PHP_EOL, $collection->id());
}統一
// 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);
}紅寶石
詳細了解不同類型的查詢。