how to sort the data from firebase? inside a flutter app

Question

I have been trying to sort data which i get from firebase database below is the code I tried but this throws an error:

(NoSuchMethodError: Class "String" has no instance method 'orderBy').

What is the best practice to sort the data?

dateTime: snapshot.data.documents[index].data['dateTime'].orderBy('createdAt', descending: true),

Below I am adding the code from CrudMethods.

  getData() async {
    return await Firestore.instance.collection('PlasmaRequests').orderBy('createdAt', descending: true).snapshots();
  }

Peter Haddad · Accepted Answer · 2020-07-16 05:40:21Z

1

You can't sort after retrieving, this code:

snapshot.data.documents[index].data['dateTime']

means you retrieved the snapshot, and you are getting the field dateTime which is of type String.

You use orderBy() when you perform the query:

void getData() async {
var result = await Firestore.instance
  .collection("myColName")
  .orderBy('createdAt', descending: true)
  .getDocuments();
}

Check the docs:

https://firebase.google.com/docs/firestore/query-data/order-limit-data

answered Jul 16, 2020 at 5:40

Peter Haddad

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5 Comments

saiveda Over a year ago

Hi thank you. I am new to development its been not more then a month. I made changes to getData as per your suggested code but no data is being retrieved and the page is empty. I am really struck at this from couple of days.

Peter Haddad Over a year ago

where are u using getData()?

saiveda Over a year ago

in My crudmethods. I just added that code below my first code.

Peter Haddad Over a year ago

did u get data before?

saiveda Over a year ago

My code was not well formatted in question before. I made changes now. I have sent a tweet as well for guidance on this please check.

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