Develop Reference

add/overwrite field of type array in Firestore

I want to add a field of type array inside a collection.
if the field doesn't exist create it. if it exists overwrite it with the new array value.
the field should be called macAddress and it's of type array of String
I have tried the following:
val macInput = setting_mac_text.text.toString()
val macArray = macInput.split(",")
val macList = Arrays.asList(macArray)
val data =
hashMapOf(Pair(FirebaseConstants.USER_MAC_ADDRESS, macArray))
//save it in firebase
db.collection(FirebaseConstants.ORGANIZATION)
.document(orgID + ".${FirebaseConstants.USER_MAC_ADDRESS}")
.set(FieldValue.arrayUnion(macList))
.addOnCompleteListener { task ->
if (task.isSuccessful) {
Log.d(TAG, "successfully inserted")
} else {
Log.d(TAG, " failed ${task.exception}")
}
}
also tried to insert the list itself and hash map like this
val data = hashMapOf(Pair(FirebaseConstants.USER_MAC_ADDRESS, macArray))
db.collection(FirebaseConstants.ORGANIZATION)
.document(orgID)
.set(data))
but it keeps giving me java.lang.IllegalArgumentException: Invalid data. Nested arrays are not supported
what am I doing wrong here?

You're doing three things wrong here:
FieldValue.arrayUnion() is only meant to be used as the value of a field to add elements to that field. The way you are using it now in the first sample, it's being taken as the entire contents of the document.
set() with one parameter is only intended to create or overwrite an entire document. It can't be used to update an existing document. You would have to pass in SetOptions to tell it to merge if you want an update. Or, you would simply use update() to modify an existing document.
Your code that deals with macArray and macList isn't working the way you expect. You are creating a list with one element, which is itself an array. The error message is telling you that you can't have nested arrays like this.
I suggest taking a step back and simplifying your code, removing all the moving parts that don't have to do with Firestore. Just hard code values in your Firestore update until the update works the way you want, then add in the code that works with actual values. Get one simple thing to work, then add to it. If you get an error, you will know that the code you just added was incorrect.

To overwrite an array, you would simply call the set method and have the merge option set to true:
try {
const query = await DatabaseService.queryBuilder({
collection: CollectionName,
});
return await query
.doc(insuranceId)
.set(
{ DOCUMENT_PROPERTY_HERE: ARRAY_HERE },
{ merge: true }
);
} catch (exception) {
return Promise.reject(exception);
}

How to check if record exists or not using Anko?

I am learning to fetching data from sqlite using anko. I can print the data successfully (if the record exist) but my application always crash when the data doesn't exist.
the error says:
parseSingle accepts only cursors with a single entry
I know exactly the meaning of error, I just dont know how to solve it.
here is the code for query:
fun getUserByUid(uid: Int): UserModel
{
val data = context.database.use {
val db = context.database.readableDatabase
val columns = UserModel.COLUMN_ID + "," + UserModel.COLUMN_NAME + "," + UserModel.COLUMN_API_KEY
val query = db.select(UserModel.TABLE_NAME, columns)
.whereArgs("(uid = {userId})",
"userId" to uid)
query.exec {
val rowParser = classParser<UserModel>()
parseSingle(rowParser) // this line that trigger error exception
}
}
return data
}
I tried to find count function in query or rowParser variable to check if the record exist or not but could not find it.

From the wiki page.
https://github.com/Kotlin/anko/wiki/Anko-SQLite#parsing-query-results
Parsing query results
So we have some Cursor, and how can we parse it into regular classes? Anko provides functions parseSingle, parseOpt and parseList to do it much more easily.
Method Description
parseSingle(rowParser): T Parse exactly one row
parseOpt(rowParser): T? Parse zero or one row
parseList(rowParser): List Parse zero or more rows
Note that parseSingle() and parseOpt() will throw an exception if the received Cursor contains more than one row.

Build the data structure with relationship via Firebase

I am new in noSQL and Firebase. But I want to build the structure of my database via Firebase.
I have users and a list of users lots. Structure with relationship.
So I did what's in the example:
String key = mDatabase.child("lots").push().getKey();
//create new lot
Lot lot = new Lot(fbUser.getUid(), fbUser.getEmail(), mMessage.getText().toString());
//turn to map
Map<String, Object> lotValues = lot.toMap();
Map<String, Object> childUpdates = new HashMap<>();
childUpdates.put("/lots/" + key, lotValues);
childUpdates.put("/user-lots/" + fbUser.getUid() + "/" + key, lotValues);
mDatabase.updateChildren(childUpdates);
But in the result I had this data to duplicate:
May be it's better to get this structure. I tried to find an example how to build one, because I do not want to to reinvent a wheel, but my efforts are futile so far.
Any suggestions? Thanks a lot.

What you're looking for is Pointers, which Firebase, believe it or not, DOES NOT have.
For example, if you want to have 3 lists of data:
My Posts
Recent Posts
Then you'll have to do it like this:
databaseRoot:{
Posts:{
{UNQ_KEY}:
{
title: "x",
description: "y",
authorUserID: {USERID1}
}
}
Users:{
{USERID1}
Posts:{
{UNQ_KEY_2}: {
title: "x",
description: "y"
}
}
}
}
When UNQ_KEY is created, you also create UNQ_KEY_2 under the user's userID.
To display "My Posts", you get the list under {USERID1}. To get "Recent Posts", you have to go to the Posts node.

Cannot seem to understand Firebase's JSON table

Let's say I have this JSON tree:
"employees":[
{"firstName":"John", "lastName":"Doe"},
{"firstName":"Anna", "lastName":"Smith"},
{"firstName":"Peter","lastName":"Jones"}
]
How can I do this in Firebase? Every time I create an object under "employees", with the name "firstname", it replaces the previous object with "Firstname".
I previously used Parse's tables, but since it's been taken down, then I need help learning this confusing thing.
I'm using Android.

Firebase databases have no native support for lists or arrays. If we try to store an list or an array, it really gets stored as an "object" with integers as the key names (see doc).
// we send this
['hello', 'world']
// Firebase databases store this
{0: 'hello', 1: 'world'}
In this way your tree in firebase would look like this:
{"employees":{
0:{"firstName":"John", "lastName":"Doe"},
1:{"firstName":"Anna", "lastName":"Smith"},
2:{"firstName":"Peter","lastName":"Jones"}
}
}
Using Firebase terminology we can say that node emloyees has three child nodes with IDs 0,1,2 respectively.
But saving data with integer IDs in Firebase is not recommended (see this to know why). Firebase provides a push() function that generates a unique ID every time a new child is added to the specified Firebase reference.
Here is an example from Firebase Android doc.:
//create firebase ref using your firebase url
Firebase ref = new Firebase("https://docs-examples.firebaseio.com/android/saving-data/fireblog");
Firebase postRef = ref.child("posts");
Map<String, String> post1 = new HashMap<String, String>();
post1.put("author", "gracehop");
post1.put("title", "Announcing COBOL, a New Programming Language");
postRef.push().setValue(post1);
Map<String, String> post2 = new HashMap<String, String>();
post2.put("author", "alanisawesome");
post2.put("title", "The Turing Machine");
postRef.push().setValue(post2);
And as a result in posts node we will have two childs with autogenerated ids:
{
"posts": {
"-JRHTHaIs-jNPLXOQivY": {
"author": "gracehop",
"title": "Announcing COBOL, a New Programming Language"
},
"-JRHTHaKuITFIhnj02kE": {
"author": "alanisawesome",
"title": "The Turing Machine"
}
}
}

You're probably looking for DatabaseReference.push(), which creates a new child under the location.
var employeesRef = mDatabase.child("employees");
var newEmployeeRef = employeesRef.push()
newEmployeeRef.setValue(employee);
The best place to read more about this is in the section on appending data to a list in the Firebase documentation.

OrmLite: Advanced where logic

I have these tables in an Android based application where I'm using OrmLite for the database management.
What I want to have an x number of array list depending on how many of the product type FOLDER I have.
So in this case I want to a list of products where the productId equals parentId.
So I want a list where
if(productType = FOLDER) {
if(productId = parentId){
//add product
}
}
Basically what I want to end up with, in this case three lists with each containing a list of products where parentId is the same for every product.
I've tried many things, and some works better than others, but a code I want to run actually throws a nullpointer.
DatabaseHelper dbHelper = getHelper();
List<Product> productsParents = null;
try {
Dao<Product, Integer> dao = dbHelper.getDao();
PreparedQuery<Product> prepQu = dao.queryBuilder().where()
.eq("parentId", dao.queryBuilder().selectColumns("productId").where()
.eq("productType", ProductType.FOLDER).prepare()).prepare();
productsParents = dao.query(prepQu);
} catch (SQLException e) {
...
}
This code isn't working because productParents returns null, and it does not do what I want, even though it's a slight hint. If someone know how to do this in code that would be sufficient also, or more likely a mix of java and ormlite.

Have you had a chance to RTFM around building queries? The ORMLite docs are pretty extensive:
http://ormlite.com/docs/query-builder
Your problem is that a prepared query cannot be an argument to the eq(...) method. Not sure where you saw an example of that form.
So there are a couple ways you can do this. The easiest way is to do a different query for each productType:
Where<Product, Integer> where = dao.queryBuilder().where();
where.eq("parentId", parentId).and().eq("productType", ProductType.FOLDER);
productsParents = where.query();
// then do another similar query again with ProductType.PRODUCT, ...
If you want to do just one query then you can get all products that match the parentId and then separate them using code:
Where<Product, Integer> where = dao.queryBuilder().where();
where.eq("parentId", parentId);
productsParents = where.query();
List<Product> productFolders = new ArrayList<Product>();
List<Product> productProducts = new ArrayList<Product>();
...
for (Product product : productsParents) {
if (product.getProductType() == ProductType.FOLDER) {
productFolders.add(product);
} else if (product.getProductType() == ProductType.PRODUCT) {
productProducts.add(product);
} else ...
}