Add data
- Flutter course
- Advanced
- Lesson 22/69
- 4 min
Add a document with collection().add.
Adding data
You add a new document to a collection with collection().add({...}). add generates an automatic document id and asynchronously returns a DocumentReference. The document data is given as a Map<String, dynamic>.
final ref = await db.collection('messages').add({
'text': 'Merhaba',
'sender': 'Ali',
});
print(ref.id);doc().set with an explicit id
If you want to give your own id instead of an auto-generated one, you use doc('id').set({...}). This method overwrites the document if it exists and creates it if not. add is for new documents, while set is for writing with a specific id.
await db.collection('users').doc('u1').set({
'name': 'Ali',
});Practice Add a document and print its id
Get db. Add a document with data {'text': 'Merhaba'} to the 'messages' collection. Print the id of the returned reference.
Starter code
class DocumentReference {
final String id;
DocumentReference(this.id);
}
class CollectionReference {
final String name;
final List<Map<String, dynamic>> _store;
CollectionReference(this.name, this._store);
Future<DocumentReference> add(Map<String, dynamic> data) async {
final id = 'auto-${_store.length + 1}';
_store.add(data);
return DocumentReference(id);
}
}
class FirebaseFirestore {
static final FirebaseFirestore instance = FirebaseFirestore._();
FirebaseFirestore._();
final Map<String, List<Map<String, dynamic>>> _db = {};
CollectionReference collection(String name) {
_db.putIfAbsent(name, () => []);
return CollectionReference(name, _db[name]!);
}
}
void main() async {
// belge ekle, id yazdır
}Sample solution
class DocumentReference {
final String id;
DocumentReference(this.id);
}
class CollectionReference {
final String name;
final List<Map<String, dynamic>> _store;
CollectionReference(this.name, this._store);
Future<DocumentReference> add(Map<String, dynamic> data) async {
final id = 'auto-${_store.length + 1}';
_store.add(data);
return DocumentReference(id);
}
}
class FirebaseFirestore {
static final FirebaseFirestore instance = FirebaseFirestore._();
FirebaseFirestore._();
final Map<String, List<Map<String, dynamic>>> _db = {};
CollectionReference collection(String name) {
_db.putIfAbsent(name, () => []);
return CollectionReference(name, _db[name]!);
}
}
void main() async {
final db = FirebaseFirestore.instance;
final ref = await db.collection('messages').add({
'text': 'Merhaba',
});
print(ref.id);
}Expected output
auto-1
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does the collection().add method return?
- An empty Future
- Only an error code
- An int number
- DocumentReference Correct answer
Explanation: The add method returns a DocumentReference pointing to the new auto-id document.
2 Add a document
final ref = await db.collection('messages').____({
'text': 'Merhaba',
});final ref = await db.collection('messages').add({
'text': 'Merhaba',
});Explanation: To add a new document to a collection you use the add method; the data is given as a Map.
3 Data writing parts
| Term | Meaning |
|---|---|
add |
Auto-id document |
doc('u1').set |
Specific-id document |
Map<String, dynamic> |
Document data |
DocumentReference |
Write result |