i am trying to update my firebase but is not appear what i updated
this is my firebase data :
and then i exported my data :
then i updated and added another class :
and return a message is all updated :
but the problem is my data don't updated and stay in same data :
and this is my rules :
please help me to know what is and why i cant success to update that
thanks alot
Firebase automatically creates keys for any values you write, and it automatically deletes keys that no longer have any values under them.
Since you specified no value for the game key, it is immediately deleted after you add it.
If you want to make sure the key gets written when you import the JSON, be sure to give it a value. E.g.
"game": true
But note that you don't need to pre-create keys like this, as Firebase will automatically create the game key when your app writes a value somewhere under it.
Related
I will first say that I am a firmware developer trying to make a web interface for a personal project. My question might be basic as this is my first web interface with a database. I have searched quite a bit on how to achieve what I am trying to do without success, so I suspect I am not approaching this the right way, but here it is:
Basically I have a device pushing data to a firebase realtime database :
the push function generates an unique Id for me automatically which is nice...
Now In my flutter interface, I want to display the latest entry on a widget so I am using the onChildAdded functionnality of flutterfire:
ref.onChildAdded.listen((DatabaseEvent event) {
print(event.snapshot.key);
print(event.snapshot.value);
});
My first issue is that this function is triggered for all the child at first before waiting for new ones which is unnecessary and could be a problem when I begin to have a lot of data. Is there a way to simply get the latest sample and still get an event when one is added? (I still want to keep the old data to be able to make charts with them)
My second problem is the format of the received data:
{
-Mx2PCeptLf2REP1YFH0: {
"picture_url": "",
"time_stamp": "2022-02-28 21:56:58.502005",
"temperature": 27.71,
"relative_humidity": 42.77,
"eco2": 691,
"tvoc": 198,
"luminosity": 4193,
"vpd": 1.71
}
}
before using the put method, I didn't have the automatically generated ID so I was able to cast this as a Map<String, dynamic> and use the data like this in my widget:
Text(snapshot.data!["temperature"].toString())
but now the added nesting with the generated id is giving me a headache as I can't seem to figure out how to simply get the data.
So if anyone could help me to always get the single latest data when subscribing to a collection and how to access that data within my State of my StatefulWidget that would be much appreciated!
My first issue is that this function is triggered for all the child at first before waiting for new ones which is unnecessary and could be a problem when I begin to have a lot of data.
The Firebase Realtime Database synchronizes the state of the path/query that you listen to. So it doesn't just fire an event on onChildAdded for new data, but also for any existing data that you request. There is (intentionally) no way to change that behavior.
So your options here are limited:
You can remove the data that your application has processed, so that it doesn't get passed to the clients again. That means you essentially implement a message-passing mechanism on top of Firebase's data-synchronization semantics.
You can use a query to only request a certain subset of the child nodes at a path. For example, if you remember the latest key that you've received, you can get data from there on with ref.orderByKey().startAt("-Mx2LastKeyYouAlreadySaw").
Since this comes up regularly, I recommend also checking:
How can I setup Firebase to observe only new data?
How to get only updated data Firebase
How to fetch only latest specific data from Firebase?
and more from these search results
My second problem is the format of the received data:
The screenshot of your database shows two keys, each of which has a single string value. The contents of that value may be JSON, but the way they are stored is just a single string.
If you want to get a single property from the JSON, you either have to:
Decode the string back into JSON with jsonDecode.
Fix the problem at the source by storing the data as proper JSON, rather than as a string.
enter image description hereHow to retrieve data from firebase database and how to assign that values to variables in react native
How can I get these two values into variables using simple way.
I think the firebase docs are pretty good and give a good explanation of how to use it.
https://firebase.google.com/docs/database/web/read-and-write
To be short:
once you have specified a reference, ex. let users = firebase.database().ref('users/' + userId), you can read the data either once using the .once() method or add a listener for changes in the data using on().
You receive a snapshot from either of these methods, and need to call snapshot.val() to retrieve the data.
Simply assign the snapshot.val() to a variable declared outside of the reading method, and you're good to go.
You can also reference a simple project I made using React-Native and firebase here: https://github.com/liplylie/rnChallenge
So, from Firebase functions, I'm listening to this event -
exports.populateVairations_delete =
functions.database.ref('/parentA/parentB/child').onDelete(event =>
{
// I know how to get the previous value for what I'm listening too...
val = event.data.previous.val();
...
}
This function is being invoked also when deleting the parent, which is exactly what I want.
But when deleting a parent, how do I access data from /parentA before it's being deleted?
onDelete triggers are always executed after the delete has occurred. There's no way to prevent a delete from happening with a function. Your onDelete code will be delivered an event that contains only the data that was deleted. The event object itself can't be used to see other parts of the database.
If you need to access other parts of the database inside a database trigger, you can use the Admin SDK to make those queries. There is a lot of official sample code that illustrates how to do this.
With context.resource.name you could get a string containing the data path.
Just use Admin SDK for Firebase, You can have administrator access to the firebase Db.From there, you can do basically anything with the Firebase Db
Simple question:
Will all obersvers automatically removed when I use goOffline (disconnect to firebase) ?
If not, is there another way to do it, because removeAllOberserves doesn't seem to work or must I keep an array of single handles?
UPDATE
I answer myself.
removeAllOberserves works well, if you call it with the reference you used to set the observer!
Example:
Firebase *userThreadRef;
userThreadRef = [userRef appendPathComponent: ThreadsPath];
[userThreadRef observeEventType: FEventTypeChildAdded withBlock: ^(FDataSnapshot *snapshot) {
...
}];
....
[userThreadRef removeAllObservers];
Do not use a new reference like this:
Firebase *newUserThreadRef = [userRef appendPathComponent: ThreadsPath];
[newUserThreadRef removeAllObservers];
Will all observers automatically removed when I use goOffline (disconnect to firebase) ?
No. Calling goOffline() will not automatically remove observers/listeners.
is there another way to do it, because removeAllOberserves doesn't seem to work or must I keep an array of single handles?
It's hard to say without seeing your code, but likely your expectations are just wrong.
You'll need to call removeAllObservers() on each reference. The All in the method name is for the fact that it removes the observers for all event types, not for all references.
I'm dealing with a problem where a user can update a document within a specified time limit, and if he doesn't, the server will.
The update involves incrementing a value and adding an object to an array of a document. I need to ensure that only one of the user/server updates the document. Not both.
To ensure this happens, some checks are run to see if the document has already been updated, but there are times where the user and server run at exactly the same time and both pass the checks and then the document is updated twice.
I've been trying many different ways of fixing this, but I haven't been able to. I tried implement a lock similar to this: http://en.wikipedia.org/wiki/Peterson%27s_algorithm to ensure that only one update will happen and the second update will fail, but I haven't been successful. Any ideas?
To ensure this happens, some checks are run to see if the document has already been updated, but there are times where the user and server run at exactly the same time and both pass the checks and then the document is updated twice.
You can achieve this by using a MongoDB update query that simultaneously checks if the value has been updated and updates it. Like this:
var post = Posts.findOne("ID");
// ... do some stuff with the post ...
Posts.update({counter: post.counter}, {$push: {items: newItem}, $inc: {counter: 1}});
As you can see, in one query we both check the counter and increment it - so if two of these queries run one right after another only one will actually update the document (since the counter won't match anymore).