Flutter Recipes 2 - Firebase Firestore Helpers

Damodar Lohani

Damodar Lohani

Web and Mobile Developer

I have built quite a few apps with Flutter and Firebase. And, for most of those projects I used Firestore as the database. So, I had to perform all sorts of query, pagination, mapping Firestore returned Maps to data models. So over that period of time, I have created a simplified, generalized helper class with various methods that help me work with firestore database. That is what I am publishing here. Hope it will be useful for those using firestore in their database.

The Source Code

This class has the most commonly used methods on firestore. It can get list of items from collection, single item, remove item, add item. It provides list and single item both as a future and stream. It also provides methods for easier query and simple paginations. It uses generic type so that, we can use it to convert firestore map to the required data model we want. This class is available as a part of firebase_helpers package.

/// The base database service class that you can instiantiate or extend
///
/// ```dart
/// DatabaseService<Note> noteDBs = DatabaseService<Note>("notes",fromDS: (id,data) => Note.fromDS(id,data), toMap: (note)=>note.toMap());
/// noteDBs.getQueryList()
/// .then((List<Note> notes)=>print(notes));
/// ```
///
class DatabaseService<T> {
/// path of the collection to use as base path for all the operations
String collection;
final FirebaseFirestore _db = FirebaseFirestore.instance;
///
/// Function to convert the firestore [DocumentSnapshot] into the model class [T]
/// provides [id] and [Map<String,dynamic> data] and must return [T] object.
///
final T Function(String, Map<String, dynamic>) fromDS;
///
///Function to convert object [T] to [Map<String,dynamic>], receives instance of [T],
///and should always return [Map<String,dynamic>]
///
final Map<String, dynamic> Function(T) toMap;
/// Create instance of Database service
/// [collection] path is required
/// [fromDS] is required to get document snapshot as object [T]
///
DatabaseService(this.collection, {this.fromDS, this.toMap});
/// Returns instance of FirebaseFirestore
FirebaseFirestore get db => _db;
/// Get a single document of [id] from the [collection]
/// Returns null if the document does not exist
Future<T> getSingle(String id) async {
var snap = await _db.collection(collection).doc(id).get();
if (!snap.exists) return null;
return fromDS(snap.id, snap.data());
}
/// Returns a single document of [id] from [collection]
/// as stream so that updates can be listened
Stream<T> streamSingle(String id) {
return _db
.collection(collection)
.doc(id)
.snapshots()
.map((snap) => snap.exists ? fromDS(snap.id, snap.data()) : null);
}
/// Returns list of all the documents from [collection]
/// as a stream so that changes can be listened
Stream<List<T>> streamList() {
var ref = _db.collection(collection);
return ref.snapshots().map(
(list) => list.docs.map((doc) => fromDS(doc.id, doc.data())).toList());
}
/// Returns the list of documents from [collection], in the order provided in
/// [orderBy] and matches the [args] supplied.
/// use [startAfter], [startAt], [endAt], [endBefore] to perform cursor based queries
/// and pagination of data
Future<List<T>> getQueryList({
List<OrderBy> orderBy,
List<QueryArgs> args,
int limit,
dynamic startAfter,
dynamic startAt,
dynamic endAt,
dynamic endBefore,
}) async {
CollectionReference collref = _db.collection(collection);
Query ref;
if (args != null) {
for (final arg in args) {
if (arg is QueryArgsV2) {
if (ref == null)
ref = collref.where(
arg.key,
isEqualTo: arg.isEqualTo,
isGreaterThan: arg.isGreaterThan,
isGreaterThanOrEqualTo: arg.isGreaterThanOrEqualTo,
isLessThan: arg.isLessThan,
isLessThanOrEqualTo: arg.isLessThanOrEqualTo,
isNull: arg.isNull,
arrayContains: arg.arrayContains,
arrayContainsAny: arg.arrayContainsAny,
whereIn: arg.whereIn,
);
else
ref = ref.where(
arg.key,
isEqualTo: arg.isEqualTo,
isGreaterThan: arg.isGreaterThan,
isGreaterThanOrEqualTo: arg.isGreaterThanOrEqualTo,
isLessThan: arg.isLessThan,
isLessThanOrEqualTo: arg.isLessThanOrEqualTo,
isNull: arg.isNull,
arrayContains: arg.arrayContains,
arrayContainsAny: arg.arrayContainsAny,
whereIn: arg.whereIn,
);
;
} else {
if (ref == null)
ref = collref.where(arg.key, isEqualTo: arg.value);
else
ref = ref.where(arg.key, isEqualTo: arg.value);
}
}
}
if (orderBy != null) {
orderBy.forEach((order) {
if (ref == null)
ref = collref.orderBy(order.field, descending: order.descending);
else
ref = ref.orderBy(order.field, descending: order.descending);
});
}
if (limit != null) {
if (ref == null)
ref = collref.limit(limit);
else
ref = ref.limit(limit);
}
if (startAfter != null && orderBy != null) {
ref = ref.startAfter([startAfter]);
}
if (startAt != null && orderBy != null) {
ref = ref.startAt([startAt]);
}
if (endAt != null && orderBy != null) {
ref = ref.endAt([endAt]);
}
if (endBefore != null && orderBy != null) {
ref = ref.endBefore([endBefore]);
}
QuerySnapshot query;
if (ref != null)
query = await ref.get();
else
query = await collref.get();
return query.docs.map((doc) => fromDS(doc.id, doc.data())).toList();
}
/// Returns the list of documents from [collection], in the order provided in
/// [orderBy] and matches the [args] supplied as a stream so that changes can be
/// listened.
/// Use [startAfter], [startAt], [endAt], [endBefore] to perform cursor based
/// queries and pagination of data
Stream<List<T>> streamQueryList({
List<OrderBy> orderBy,
List<QueryArgs> args,
int limit,
dynamic startAfter,
dynamic startAt,
dynamic endBefore,
dynamic endAt,
}) {
CollectionReference collref = _db.collection(collection);
Query ref;
if (orderBy != null) {
orderBy.forEach((order) {
if (ref == null)
ref = collref.orderBy(order.field, descending: order.descending);
else
ref = ref.orderBy(order.field, descending: order.descending);
});
}
if (args != null) {
for (final arg in args) {
if (arg is QueryArgsV2) {
if (ref == null)
ref = collref.where(
arg.key,
isEqualTo: arg.isEqualTo,
isGreaterThan: arg.isGreaterThan,
isGreaterThanOrEqualTo: arg.isGreaterThanOrEqualTo,
isLessThan: arg.isLessThan,
isLessThanOrEqualTo: arg.isLessThanOrEqualTo,
isNull: arg.isNull,
arrayContains: arg.arrayContains,
arrayContainsAny: arg.arrayContainsAny,
whereIn: arg.whereIn,
);
else
ref = ref.where(
arg.key,
isEqualTo: arg.isEqualTo,
isGreaterThan: arg.isGreaterThan,
isGreaterThanOrEqualTo: arg.isGreaterThanOrEqualTo,
isLessThan: arg.isLessThan,
isLessThanOrEqualTo: arg.isLessThanOrEqualTo,
isNull: arg.isNull,
arrayContains: arg.arrayContains,
arrayContainsAny: arg.arrayContainsAny,
whereIn: arg.whereIn,
);
} else {
if (ref == null)
ref = collref.where(arg.key, isEqualTo: arg.value);
else
ref = ref.where(arg.key, isEqualTo: arg.value);
}
}
}
if (limit != null) {
if (ref == null)
ref = collref.limit(limit);
else
ref = ref.limit(limit);
}
if (startAfter != null && orderBy != null) {
ref = ref.startAfter([startAfter]);
}
if (startAt != null && orderBy != null) {
ref = ref.startAt([startAt]);
}
if (endAt != null && orderBy != null) {
ref = ref.endAt([endAt]);
}
if (endBefore != null && orderBy != null) {
ref = ref.endBefore([endBefore]);
}
if (ref != null)
return ref.snapshots().map((snap) =>
snap.docs.map((doc) => fromDS(doc.id, doc.data())).toList());
else
return collref.snapshots().map((snap) =>
snap.docs.map((doc) => fromDS(doc.id, doc.data())).toList());
}
/// Returns the list of documents from [from] date to [to] date matched by [field]
/// is ordered by the [field] provided.
/// additional [args] can be supplied to perform specific query.
Future<List<T>> getListFromTo(String field, DateTime from, DateTime to,
{List<QueryArgs> args = const []}) async {
var ref = _db.collection(collection).orderBy(field);
for (final arg in args) {
if (arg is QueryArgsV2) {
ref = ref.where(
arg.key,
isEqualTo: arg.isEqualTo,
isGreaterThan: arg.isGreaterThan,
isGreaterThanOrEqualTo: arg.isGreaterThanOrEqualTo,
isLessThan: arg.isLessThan,
isLessThanOrEqualTo: arg.isLessThanOrEqualTo,
isNull: arg.isNull,
arrayContains: arg.arrayContains,
arrayContainsAny: arg.arrayContainsAny,
whereIn: arg.whereIn,
);
} else {
ref = ref.where(arg.key, isEqualTo: arg.value);
}
}
QuerySnapshot query = await ref.startAt([from]).endAt([to]).get();
return query.docs.map((doc) => fromDS(doc.id, doc.data())).toList();
}
/// Returns the list of documents from [from] date to [to] date matched by [field] from [collection]
/// as a stream so that changes can be listened and is ordered by the [field] provided.
/// additional [args] can be supplied to perform specific query.
Stream<List<T>> streamListFromTo(String field, DateTime from, DateTime to,
{List<QueryArgs> args = const []}) {
var ref = _db.collection(collection).orderBy(field, descending: true);
for (final arg in args) {
if (arg is QueryArgsV2) {
ref = ref.where(
arg.key,
isEqualTo: arg.isEqualTo,
isGreaterThan: arg.isGreaterThan,
isGreaterThanOrEqualTo: arg.isGreaterThanOrEqualTo,
isLessThan: arg.isLessThan,
isLessThanOrEqualTo: arg.isLessThanOrEqualTo,
isNull: arg.isNull,
arrayContains: arg.arrayContains,
arrayContainsAny: arg.arrayContainsAny,
whereIn: arg.whereIn,
);
} else {
ref = ref.where(arg.key, isEqualTo: arg.value);
}
}
var query = ref.startAfter([to]).endAt([from]).snapshots();
return query.map(
(snap) => snap.docs.map((doc) => fromDS(doc.id, doc.data())).toList());
}
/// Creates new document based on the provided [item] and [id] in the [collection]
/// If [id] is null, [id] will be auto generated by firestore
///
@Deprecated("Use create(Map<String,dynamic> data, {String id}) instead.")
Future<dynamic> createItem(T item, {String id}) {
if (id != null) {
return _db.collection(collection).doc(id).set(toMap(item));
} else {
return _db.collection(collection).add(toMap(item));
}
}
/// Creates new document based on the provided [data] and [id] in the [collection]
/// If [id] is null, [id] will be auto generated by firestore
///
Future<dynamic> create(Map<String, dynamic> data, {String id}) {
if (id != null) {
return _db.collection(collection).doc(id).set(data);
} else {
return _db.collection(collection).add(data);
}
}
///
/// Updates the document with [id] with the provided [data] to the [collection]
///
Future<void> updateData(String id, Map<String, dynamic> data) {
return _db.collection(collection).doc(id).update(data);
}
/// Removes item with [id] from [collection]
Future<void> removeItem(String id) {
return _db.collection(collection).doc(id).delete();
}
}
/// Supply query to query the data based on [key] field with [value]
/// Always performs `isEqualTo` query
@Deprecated("Use QueryArgsV2 instead")
class QueryArgs {
final dynamic key;
final dynamic value;
QueryArgs(this.key, this.value);
}
/// Supply query to query the collection based on [key] field and the
/// values supplied to various arguments
/// Please refer to firestore documentation for understanding
/// various operators of the query
class QueryArgsV2 extends QueryArgs {
/// Field to match
final dynamic key;
/// performs equality == check
final dynamic isEqualTo;
/// performs less than < check
final dynamic isLessThan;
/// performs less than or equal to <= check
final dynamic isLessThanOrEqualTo;
/// performs greater than or equal to >= check
final dynamic isGreaterThanOrEqualTo;
/// performs greater than > check
final dynamic isGreaterThan;
/// performs array contains check
final dynamic arrayContains;
/// performs array contains any check
final List<dynamic> arrayContainsAny;
/// performs where in check
final List<dynamic> whereIn;
/// performs if is null check
final bool isNull;
/// Create instance of QueryArgsV2
QueryArgsV2(this.key,
{this.isEqualTo,
this.isLessThan,
this.isLessThanOrEqualTo,
this.isGreaterThan,
this.arrayContains,
this.arrayContainsAny,
this.whereIn,
this.isNull,
this.isGreaterThanOrEqualTo})
: super(key, isEqualTo);
}
/// Provide ordering option to queries
class OrderBy {
/// Field to order by
final String field;
/// Whether the order should be descending, default is false
final bool descending;
/// Creates instance of OrderBy
OrderBy(this.field, {this.descending = false});
}

Below I will show how to use this package to get a list of Note items from notes collection.

Adding Dependency and importing

First add it's dependency to the pubspec.yaml file.

dependencies:
firebase_helpers: latest

Then where you want to use it's methods, you can import it

import 'package:firebase_helpers/firebase_helpers';

Create a model

We create a notes item model for our data

class Note{
final String title;
final String id;
final String description;
final DateTime createdAt;
final String userId;
Note({this.title, this.id, this.description, this.createdAt, this.userId});
Note.fromDS(String id, Map<String,dynamic> data):
id=id,
title=data['title'],
description=data['description'],
userId=data['user_id'],
createdAt=data['created_at']?.toDate();
Map<String,dynamic> toMap() => {
"title":title,
"description":description,
"created_at": createdAt,
"user_id": userId,
};
}

Instiantiate database service with specific type

We instantiate the generic class using the Note model as our type. Pass the collection path as notes and provide functions to convert from DocumentSnapshot to note and note to Map

DatabaseService<Note> notesDb = DatabaseService<Note>("notes",fromDS: (id,data) => Note.fromDS(id,data), toMap:(note) => note.toMap() );

Insert new item to firestore

Finally we can use notesDb instance to work with notes collection in our Firestore. For example to create item

Note note = Note(
title: "Hello Note",
description: "This is notes description",
);
notesDb.create(note.toMap()); //this function will add our note item to the firestore database

Github Repository

https://github.com/lohanidamodar/flutter_firebase_starter