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How to only get new data without existing data from a Firebase?


How to only get new data without existing data from a Firebase?

By : Ayub Subhani
Date : November 28 2020, 09:01 AM
will help you I have a node in Firebase getting continually updated with information from a logfile. The node is lines/ and each child of lines/ is from a post() so it has a unique ID. , You need to include a timestamp property and run a query.
code :
// Get the current timestamp
var now = new Date().getTime();
// Create a query that orders by the timestamp
var query = ref.orderByChild('timestamp').startAt(now);
// Listen for the new children added from that point in time
query.on('child_added', function (snap) { 
  console.log(snap.val()
});

// When you add this new item it will fire off the query above
ref.push({ 
  title: "hello", 
  timestamp: Firebase.ServerValue.TIMESTAMP 
});


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When I try to save data to Firebase it only updates the existing data, Swift, Firebase

When I try to save data to Firebase it only updates the existing data, Swift, Firebase


By : Emily
Date : March 29 2020, 07:55 AM
wish help you to fix your issue The way I set up my database structure was like this: , More idiomatic is to store the list of items with so-called push ids:
code :
Lists
  twEymn...
    -Km....: "Yoghurt"
self.ref.child("Lists").child(user!.uid).childByAutoId().setValue(item)
Lists
  twEymn...
    "Yoghurt": true
self.ref.child("Lists").child(user!.uid).child(item).setValue(true)
Firebase Make Existing Data Unmodifiable but can write and read new data

Firebase Make Existing Data Unmodifiable but can write and read new data


By : sohfix_0311
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further You forgot to add the user id in your rules. Right now nobody will be able to write after the first user has added his data. To fix this simply add a wildcard path for the user id in your rules like this:
code :
{
  "rules": {
    "users":{
      ".read": true,
      "$userid":{
        ".write": "!data.exists() && newData.exists()"
      }
    }
  }
}
Firebase database write permission rules using newValue and data to access existing data

Firebase database write permission rules using newValue and data to access existing data


By : Wang Jin
Date : March 29 2020, 07:55 AM
this one helps. newData won't exist for deletes, so you will need to guard against that to avoid the first part of your rule failing:
code :
(
  newData.exists() &&
  root.child('permisos').child('owners').child(auth.uid).child(newData.child('client').val()).exists()
) ||
root.child('permisos').child('owners').child(auth.uid).child(data.child('client').val()).exists()
Swift iOS: Inserting data into Firebase database overwrites existing data

Swift iOS: Inserting data into Firebase database overwrites existing data


By : Joao Domingos
Date : March 29 2020, 07:55 AM
it fixes the issue That's the whole point. When you insert an object, the whole earlier object gets overwritten.
For example, if you have an object at a path uid.messages.messageid and you save to said messageid, the whole object will get overwritten. Thus, you basically need to have the old object, make changes to it, and save it back.
Firebase. how to save data as transactions without overwriting the existing data, but updating it? Swift3

Firebase. how to save data as transactions without overwriting the existing data, but updating it? Swift3


By : Erşan Işık
Date : March 29 2020, 07:55 AM
To fix this issue When you run a transaction, your callback/handler is invoked with the existing data in the location. So all you do is update the properties that you want modified and return that combination from your callback/handler.
There is no way to just tell the client what properties to update. But since your handler is invoked with the existing value from the location it's updating, that should not lead to inefficiencies in the code.
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