Firebase-Dart Filtering Data - firebase

Question

My data is something like this:
{
"members": [
{
"type": "alpha",
"name": "John"
},
{
"type": "alpha",
"name": "Jane"
},
{
"type": "beta",
"name": "Renata"
},
{
"type": "beta",
"name": "Richard"
}
]
}
If I access it as follows, I get the list of all members:
DatabaseReference ref = database().ref('members')
ref.onValue.listen((e) {
var members = e.snapshot.val();
});
However, if I try to filter the data, as follows, I get null.
DatabaseReference ref = database().ref('members').orderByValue().equalTo("alpha", "type");
ref.onValue.listen((e) {
var members = e.snapshot.val();
});
How do I get only objects with "type" "alpha"?

Answer 1

Your members reference corresponds to a List of objects, and none of the immediate children in the List are strings like "alpha" so your orderByValue().equalTo() query returns null. The "type" argument you're passing is searching on indices in the list (0, 1, etc.) rather than keys in the child objects ("type", "name").
Instead, you can use orderByChild():
DatabaseReference ref = database().ref().child('members').orderByChild("type").equalTo("alpha");
You may find that you get a List with some holes in it, if the alphas aren't at the beginning:
[{name: John, type: alpha}, null, {name: Jane, type: alpha}]
You can remove the null values with
members = new List<Object>.from(members)..remove(null);