How to delete certain children of Firestore field array using Flutter

Question

I am trying to make a Flutter and Firebase fitness application that saves runs a user logs. The runs are saved in an array called 'runs' in the Firestore database. Each document in my database represents a different user's runs, so the 'runs' array is a field found within each user's document. I have been trying to delete only a specific child of 'runs' but have had no luck. Does anyone know how to do this?

Here is my code for the delete function:

final CollectionReference runCollection = Firestore.instance.collection('runs')

Future deleteRun(dynamic runToDelete) async {
    return await runCollection.document(uid).setData({
      'runs': FieldValue.arrayRemove([runToDelete])
    });
  }

When I run this, I get no errors but nothing happens in the database.

I have also tried FieldValue.delete() but have not been able to isolate a specific index of 'runs' to delete without deleting the entire array.

Here is a picture of my firestore database:

Please edit the question to show the exact contents of the document you're trying to change, and the exact value of runToDelete. Without these, we have no idea if you might be doing something wrong. — Doug Stevenson
– Doug Stevenson, Commented May 12, 2020 at 22:11
By the way runCollection.document(uid) will always be non-null. It is not actually querying the database, it is just building a reference to a document that might exist or not. — Doug Stevenson
– Doug Stevenson, Commented May 12, 2020 at 22:14
@DougStevenson runToDelete is of type Map<String, dynamic> and includes data about the run. 'runs' is a list of these maps — ns90001
– ns90001, Commented May 13, 2020 at 3:22
Please edit the question to show the exact document and data. Use the edit link at the bottom of the question to make changes. — Doug Stevenson
– Doug Stevenson, Commented May 13, 2020 at 3:24
If possible, add a screenshot from your database as well, so we have a deeper understanding of your structure. — gso_gabriel
– gso_gabriel, Commented May 13, 2020 at 12:58

Arghya Sadhu · Accepted Answer · 2020-08-31 12:14:43Z

3

Firestore.instance.collection(collection name).document(your document id).updateData({"array name": FieldValue.arrayRemove([delete object/array])}).than((value){print("delete");}).catchError((error){print(error);});

edited Aug 31, 2020 at 12:14

Arghya Sadhu

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answered Aug 31, 2020 at 12:03

jaydip Patel

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2 Comments

Adrian Mole Over a year ago

While this code may solve the question, including an explanation of how and why this solves the problem would really help to improve the quality of your post, and probably result in more up-votes. Remember that you are answering the question for readers in the future, not just the person asking now. Please edit your answer to add explanations and give an indication of what limitations and assumptions apply.

mark gichohi Over a year ago

on this answer what worked for me is '''Firestore.instance.collection(collection name).document(your document id).updateData({"array name": FieldValue.arrayRemove(delete object/array)}).then((value){print("delete");}).catchError((error){print(error);});'''

Doug Stevenson · Accepted Answer · 2020-05-15 17:31:52Z

0

FieldValue.delete() only works when you know the entire contents of the array item to delete. It does not work with indexes, nor does it work with child values of array items.

What you will have to do instead is read the document, modify the array in memory, then write the modified array back to the document.

answered May 15, 2020 at 17:31

Doug Stevenson

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1 Comment

Doug Stevenson Over a year ago

These operations are all well documented. If you have a specific problem, please post a new question with the code that isn't working the way you expect.

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