Firestore: what's difference between Firebase.firestore and FirebaseFirestore.getInstance()

Question

What's difference between Firebase.firestore and FirebaseFirestore.getInstance()?

When do I want to update DB, which one is appropriate for this purpose?

And when I want to check the extracted result value from Firestore.

if I log it, it only prints the object name not result in string value that is contained in the object.

db.collection("users").whereEqualTo("userId", userId?.toInt())
  .get()
  .addOnSuccessListener {
    documents - >
      for (document in documents) {
        Log.d("결과", documents.toString())
      }
  }

If I print this, it throws result like below:

com.google.firebase.firestore.QuerySnapshot@b38fd47b

I want to read fields and values of this QuerySnapshot, how can I do this?

share code and error:

var db = Firebase.firestore

        val stDocRef = db.collection("users").whereEqualTo("userId", userId?.toInt())
        db.runTransaction { transaction ->
            transaction.update(stDocRef,"name", "new name")
            null
        }.addOnSuccessListener {  Log.d("결과", "Transaction success!") }

Aside from m y answer, since you're using Kotlin, I think that this [resource](https://medium.com/firebase-tips-tricks/how-to-read-data-from-cloud-firestore-using-get-bf03b6ee4953) will help. Here is the corresponding [repo](https://github.com/alexmamo/CloudFirestore/). — Alex Mamo, Dec 31 '22 at 09:29

krishnaacharyaa · Answer 1 · 2022-12-31T07:38:53.440

0

You are trying to print the QuerySnapshot Object , Hence it is giving you the Memory Address of the Object. To overcome this, try to print document.data as show in the below example.

According to docs use Firebase.firestore to initialize the db

val db = Firebase.firestore // Access a Cloud Firestore instance from your Activity

Refer the following links for CRUD operation in firebase with kotlin :

edited Dec 31 '22 at 07:38

answered Dec 31 '22 at 03:17

krishnaacharyaa

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Thanks I use kotlin can i get language of kotlin of this code? – Hyejung Dec 31 '22 at 04:22
I have updated my code to contain kotlin . For more reference refer https://firebase.google.com/docs/firestore/manage-data/transactions – krishnaacharyaa Dec 31 '22 at 07:15
my code throws error message: Create extension function 'Transaction.update' I guess update function doesn't exist in transaction.. it is same for document.data. data is underlined with red line. can you guess any reason? – Hyejung Dec 31 '22 at 07:26
See the updated code for adding firebasedata – krishnaacharyaa Dec 31 '22 at 07:35
I add code and error shot on my post – Hyejung Dec 31 '22 at 07:38
I have posted the equivalent docs based on your demand. Please check out which suits for you – krishnaacharyaa Dec 31 '22 at 07:42

score 0 · Accepted Answer · answered Dec 31 '22 at 09:29

What's the difference between Firebase.firestore and FirebaseFirestore.getInstance()?

None. Both are creating the same instance. The first instance is created by using an extension property of the Firebase class, while the second one is creating an instance using the getInstance() method of the FirebaseAuth. The latter one is also a singleton.

If I log it, it only prints the object name, not the result string value which is contained in the object.

That's the expected behavior, since your calling toString() on the documents object:

Log.d("결과", documents.toString())
//

The documents that comes from the lambda expression is actually a document of type QuerySnapshot which:

contains the results of a query. It can contain zero or more DocumentSnapshot objects.

So you have to loop through the documents, as you already and get the data according to the type of the field:

.addOnSuccessListener { documents - >
    for (document in documents) {
      Log.d("결과", document.getString("userId"))
      //                        
    }
}

If you however want to run a transaction, which in my opinion doesn't make any sense, since you're only reading data, then please check the documentation, or my answer from the following post:

Can I make firestore transaction that reads from firestore, but write on the realtime database?

Firestore: what's difference between Firebase.firestore and FirebaseFirestore.getInstance()

2 Answers2