Add an item to a list in Firebase Database

Question

I have the following Firebase database structure. uIds is a type of List. I am trying to add another uId under uIds with

Answer 1

There is a good old article from the Firebase official blog explaining why we should avoid array in our database : Arrays are Evil

So it's not possible to modify an array without replacing the array. I suggest to change your database structure to this

"requests" : {
    "" : {
        "interests" : [ "x" ],
        "live" : true,
        "uIds" : {
            "" : "user1",
            "" : "user2"
        }
    },
    "" : {
        "interests" : [ "y" ],
        "live" : true,
        "uIds" : {
            "" : "user2"
        }
    }
}

To get the pushKey, you can use push() method (the same as what you have done to each Request item)

Then the code will be like this if you just want to add a new uid to a request.

String requestKey = "request001";
mDatabase.child("requests").child(requestKey).child("uIds").push().setValue("user2");

Comment here if you have questions, hope this helps :)