How can I access each document id in Firebase? - flutter

Question

In my blogapp ,I am trying to implement comment system in flutter using cloud firestore. Each document is a post and I am trying to add comments as a subcollection to each document. How can I access each document id so that I can access the subcollection ?
Here I tried to print the document id below but it shows error NoSuchMethodError: 'id' method not found Receiver: null Arguments: [] :
final ref = await FirebaseFirestore.instance
.collection('blogs')
.add({
'title': titleController.text,
'body': myController.text,
'author': name,
'date': DateFormat('dd/MM/yyyy,hh:mm')
.format(DateTime.now()),
})
.then((value) => successAlert(context))
.catchError((error) =>
errorAlert(context));
titleController.clear();
myController.clear();
print(ref.id);
}
This is my firestore database :

Answer 1

You need to have access to the document id inside blogs, and access it's collection and the add your data like this...
await FirebaseFirestore.instance
.collection('blogs')
.doc(documentId) // you need to enter this document id
.collection('comments').add({
'title': titleController.text,
'body': myController.text,
'author': name,
'date': DateFormat('dd/MM/yyyy,hh:mm')
.format(DateTime.now()),
})

Answer 2

When you dont have the document id Firebase provides the get() command which returns the content of a collection. Like this:
db.collection("cities").get().then((res) => print("Successfully completed"), onError: (e) => print("Error completing: $e"));
But i realize that you will need the document id, so to get this you have to store the id after inserting a post, i've an example from a personal project:
await firestore.collection('item').add({
'quantity': element.quantity,
'product_id': element.product.productId,
}).then((value) {
/// Here you can access [value.id] to get this document id.
/// Now you can save it in a list or a class instance. Just keep it.
})
Now you can use the document id to update the post with a new comment, like this. For more information we have the Firestore documentation with flutter code snipets.