I'm trying to update a property in a record in Firebase Database, with AngularJS. I can set up a query to find my record:
firebase.database().ref('en/').orderByChild('word').equalTo('the').once('value')
.then(function(snapshot) {
snapshot.forEach(function(childSnapshot) {
console.log(childSnapshot.val())
});
})
I can update my property, if I hardcode in the record's key:
firebase.database().ref('en/-KloeQHDC-mugPjJMAG4').update({ wordFrequency: 111 })
But if I set up a query to find the record and then update it, I get an error message update is not a function:
firebase.database().ref('en/').orderByChild('word').equalTo('the').update({ wordFrequency: 9001 })
Another answer suggests calling update() from inside a forEach loop:
firebase.database().ref('en/').orderByChild('word').equalTo('the').once('value')
.then(function(snapshot) {
snapshot.forEach(function(childSnapshot) {
console.log(childSnapshot.val()); // this works
childSnapshot.ref().update({ wordFrequency: 9001 });
});
});
That returns an error message TypeError: childSnapshot.ref is not a function. I don't see how childSnapshot is a Firebase ref.
Another answer says
When you call update() on a location, Firebase loops over the data
that you pass in (in your case asJson) and for each key performs a
ref.child(key).set(value).
If update() loops over the data, why should I call update() from inside a forEach loop? The documentation doesn't show calling update() from inside a forEach loop.
The Firebase Database SDK provides a Reference.update() method to update data in a single location in a database. Key here is that a Reference is a single location in the database, so it is clear what to update.
My pseudo-code explanation about how multi-path updates work applies to how the database server implements it: given a single location/DatabaseReference it updates each path in the update() call based on that.
A Query can match multiple locations in the database, so it doesn't have an update() method (or set() or remove() for that matter).
To update each location matched by a query, you execute the query and then call update() on each result - either by a child_added listener, or with a value listener and a loop like in your last snippet.
After I posted this question I walked the dog, ate dinner, and then the solution came to me. My new rule is, "The key to Firebase queries is to keep track of the key."
This template is for users to update records in the database. They enter a search term in a form field and click the "Search" button. The $scope.search handler queries the Firebase database and then populates the form fields with the record's properties:
$scope.search = function() {
myFirebase_ref.orderByChild('word').equalTo($scope.word).once('value')
.then(function(snapshot) {
snapshot.forEach(function(childSnapshot) {
$scope.wordKey = childSnapshot.key;
$scope.audioArray = childSnapshot.val().audio;
$scope.ipaArray = childSnapshot.val().ipa;
$scope.language = childSnapshot.val().language;
$scope.longLanguage = childSnapshot.val().longLanguage;
$scope.phonemeArray = childSnapshot.val().phonemes;
$scope.translationArray = childSnapshot.val().translations;
$scope.word = childSnapshot.val().word;
$scope.wordFrequency = childSnapshot.val().wordFrequency;
$scope.$apply();
});
})
.catch(function(error) {
console.error("Authentication failed:", error.message);
});
};
Note at the top of the property assignments I have $scope.wordKey = childSnapshot.key;. I'm keeping track of the record's key.
The user then updates a field. Each field has a button next to it for "Update". Each button goes to a handler. For example, to update the wordFrequency field I have this handler:
$scope.updateFrequencyRank = function() {
firebase.database().ref('en/' + $scope.wordKey).update({ wordFrequency: $scope.wordFrequency })
};
One line of code and it works! Even better, I made an onComplete function to tell me if the update succeeded:
$scope.updateFrequencyRank = function() {
var onComplete = function(error) {
if (error) {
console.log('Update failed');
} else {
console.log('Update succeeded');
}
};
firebase.database().ref('en/' + $scope.wordKey).update({ wordFrequency: $scope.wordFrequency }, onComplete);
};
Related
I'm using Firebase Functions with the "Spark Plan" (free). This is part of my function:
return query.once("value").then(function(snapshot) {
snapshot.forEach(function(childSnapshot) {
var childData = childSnapshot.val();
if (childData.displayName === ally) {
existAlly = true;
console.log('uid: '+uid)
var ref = admin.database().ref('users/'+uid).transaction(function (current_value) {
console.log('current_value: '+uid)
current_value.mainAlly = ally;
current_value.coins = (current_value.coins || 0) + 10
return current_value;
}).then(() => {
console.log('New Ally added');
return true;
});
...
Here the logs, you can see "'current_value: null'
But, ss you can see in the next picture, the "ref" is correct:
So, is it a billing issue? The "admin.database()" stops working after a while? Or is it something else?
Thanks!
EDIT: I just did another test, and now the error is in "coins", with the same code:
Everything is working as expected. When working with transactions, you can expect that your handler function will get called the first time with null (which you will have to check for), then again with the actual contents of the database. You should review the documentation, and pay special attention to the note that says:
Transaction Function is Called Multiple Times
Your transaction handler is called multiple times and must be able to
handle null data. Even if there is existing data in your database it
may not be locally cached when the transaction function is run.
I'm creating my custom order id with auto-increment generator function for my project. I will state my question here, if you want to know the whole story please read below.
As written in the title, I need a way to reject my set to Firebase and it has to be done in 1 query. Currently, it will write my orderID to Firebase without rejecting it. But I need to reject if there is the same ID in the table.
The short version of my code will be posted here, the whole function will be posted below.
firebase.database().ref('orderCounter/orderIDsChecker/'+orderID).set({
id: orderID,
}, function(error) {
if (error) {
console.log('Order ID fail to generate. Regenerating new ID')
createOrderID(orderCounterRef);
} else {
console.log('Order ID created!')
}
});
}
The story,
I'm creating my own custom order id with auto-increment generator function for my project. The problem is that if multiple users creating order at the same time, it will generate the same id. Yes, I can use transaction() to solve the problem but I have no idea how to use it. Therefore, I have created my own version of the "transaction". With my method, I am able to prevent duplicates id unless 2 or more users create order within 1 second of gap. Or if anyone is kind enough to show me an example of how to write a transaction for my function, I thank you in advance.
The flow of the code is,
Get "currentMonth" and "orderIdCounter" from Firebase -> orderIdCounter +1 and update to Firebase -> start the process of generating order id -> Send the generated id to firebase -> If return success "order ID created", If not "got duplicate id" Re-run the whole process.
Below is the code for my order id generator function.
function createOrderID(orderCounterRef){
var childData = [];
var orderID;
//Get the Current Month and Order ID Counter from Firebase
orderCounterRef.on('value', function(snap) { childData = snapshotToArrayWithoutID(snap); });
var currentMonth = childData[0];
var orderIDCounter = childData[1];
if (orderIDCounter !== undefined){
//Update orderIDCounter on Firebase.
//This is to prevent duplicate orderID when multiple users is creating order at the same time.
var IDCounter = parseInt(orderIDCounter) + 1;
//Set IDCounter to 3 digits
IDCounter = ('00' + IDCounter.toString()).slice(-3);
firebase.database().ref('orderCounter/orderIDCounter').set(IDCounter);
//Handle the process to generate Order ID. Return in YYMMxxx(auto increment) format.
orderID = handleCreateOrderID(currentMonth, (parseInt(orderIDCounter) - 1));
//Check if duplicate ID on firebase
firebase.database().ref('orderCounter/orderIDsChecker/'+orderID).set({
id: orderID,
}, function(error) {
if (error) {
console.log('Order ID fail to generate. Regenerating new ID')
createOrderID(orderCounterRef);
} else {
console.log('Order ID created!')
}
});
}
return orderID;
}
My DB:
You should indeed use a transaction as you have mentioned in your question.
The following should do the trick:
//Declare a function that increment a counter in a transaction
function createOrderID() {
var orderIdRef = firebase.database().ref('orderId');
return orderIdRef.transaction(function(currentId) {
return currentId + 1;
});
}
//Call the asynchronous createOrderID() function
createOrderID().then(function(transactionResult) {
console.log(transactionResult.snapshot.val());
});
If you want to start the counter at a specific value, just create an orderId node in your database and assign a specific value to it, e.g; 1912000.
If you just want to start at 1, you don't need to create a node, it will be automatically created with the first call to the createOrderID() function.
Thank you, #samthecodingman & #Renaud Tarnec for your advice.
I took #samthecodingman's code and change a bit to fit my project. But I use generateOrderID() only to call the result and it works well. But you won't get any value with just the code. I call out another function (connectToFirebase) whenever users enter the page. I am not sure why it works or if this is the right way, but it works for me and that's good enough.
export function generateOrderID(){
var orderId;
var childData = [];
const orderCounterRef = firebase.database().ref('orderCounter/');
//Get the Current Month from Firebase
orderCounterRef.on('value', function(snap) { childData = snapshotToArrayWithoutID(snap); });
//Check ID format YYMMXXX (XXX=auto_increment). Hanlde auto_increment for Year and Month
handleOrderIdFormat(childData[0], orderCounterRef)
//transaction
orderCounterRef.child('orderId').transaction(function(currentId) {
orderId = (currentId||0) +1;
return orderId;
}, function(err) {
if( err ) {
console.log(err)
}
});
return orderId;
}
export function connectToFirebase(){
//Connection Firebase Database
const orderCounterRef = firebase.database().ref('orderCounter/');
orderCounterRef.on('value', function(snap) { });
}
I am faced with the problem of retrieving two data values of a single node from my firebase database and reference it in my javascript file but don't know how to go about it. I have been able to retrieve just one data value from a node (in this case "message") but I would like to add "from" as well. Most tutorials just reference one so I am really confused. So how do I get multiple data values?
This is my code...
JS file
exports.sendNotification7 = functions.database.ref('/GroupChat/{Modules}/SDevtChat/{SDevtChatId}/message')
.onWrite(( change,context) =>{
// Grab the current value of what was written to the Realtime Database.
var eventSnapshot = change.after.val();
var str = "New message from System Development Group Chat: " + eventSnapshot;
console.log(eventSnapshot);
var topic = "Management.Information.System";
var payload = {
data: {
name: str,
click_action: "Student_SystemsDevt"
}
};
// Send a message to devices subscribed to the provided topic.
return admin.messaging().sendToTopic(topic, payload)
.then(function (response) {
// See the MessagingTopicResponse reference documentation for the
// contents of response.
console.log("Successfully sent message:", response);
return;
})
.catch(function (error) {
console.log("Error sending message:", error);
});
});
You can read from however many nodes you want in a Cloud Function. However, only one can trigger the function to run.
To read from your database use the following code:
admin.database().ref('/your/path/here').once('value').then(function(snapshot) {
var value = snapshot.val();
});
You will probably want to read from the same place that the Cloud Function was triggered. Use context.params.PARAMETER to get this information. For the example you posted your code would turn out looking something like this:
admin.database().ref('/GroupChat/'+context.params.Modules+'/SDevtChat/'+context.params.SDevtChatId+'/from').once('value').then(function(snapshot) {
var value = snapshot.val();
});
Just trigger your function one level higher in the JSON:
exports.sendNotification7 =
functions.database.ref('/GroupChat/{Modules}/SDevtChat/{SDevtChatId}')
.onWrite(( change,context) =>{
// Grab the current value of what was written to the Realtime Database.
var eventSnapshot = change.after.val();
console.log(eventSnapshot);
var str = "New message from System Development Group Chat: " + eventSnapshot.message;
var from = eventSnapshot.from;
...
Working on the IndexedDB API, I'm creating many objectStores that belong to the same database, in one transaction, when the user loads a webpage.
I order to do so, I created an object which contains many objectStores to be created, each one has it's name, data and index.
Then a function runs the object and effectively creates Database, objectStores and indexes for each one.
However of all OS's created, just the last member of the object gets populated. Say of 5 objects to be created and populated, 5 are created but only the last one is populated.
Clearly is a problem of overwriting or some issue related to the JS stack or asynchronicity.
I appreciate any help to make the code populate all OS not the last one.
My browser is Chrome 56, I fetch data from an API whose response is OK, and I'm coding on vanillajs. I appreciate your help in vanillajs, there is no way to use any library or framework different from what the modern Web Platform offers.
Here is the code:
On the HTML side, this is an example of the object:
var datastores = [{osName:'items', osEndpoint: '/api/data/os/1/1', osIndex:'value'}, {osName:'categories', osEndpoint: '/api/data/os/2/1', osIndex: 'idc'}];
On javascript:
var request = indexedDB.open(DB_NAME, DB_VERSION); // open database.
request.onerror = function (e) { // error callback
console.error("error: " + e.target.errorCode);
};
request.onupgradeneeded = function (e) { // the onupgradeneeded event which creates all schema, dataabase, objectstores and populates OS.
var db = this.result;
for (var i in datastores) { // loop the objectStore object.
var objectStore = db.createObjectStore(datastores[i].osName, {keyPath: "id"});
TB_NAME = datastores[i].osName; // instantiate each objectStore name.
objectStore.createIndex(datastores[i].osIndex, datastores[i].osIndex, { unique: false }); // create each index.
objectStore.transaction.oncomplete = function(e) { // oncomplete event, after creating OS...
fetchGet(datastores[i].osEndpoint, popTable); // runs a function to fetch from a designated endpoint and calls a function.
};
}
}
Now the functions: to fetch data and to populate data:
function fetchGet(url, function) { // fetch from API.
fetch(url, {
method: 'GET'
}).then(function(response) {
return response.json();
}).then(function(json) {
popTable (json);
}).catch(function(err) {
console.log('error!', err);
});
}
function popTable(json) {
var m = 0;
var tx = db.transaction(TB_NAME, "readwrite");
tx.oncomplete = function(e) {
console.log("Completed Transaction " + TB_NAME);
};
tx.onerror = function(e) {
console.error("error: " + e.target.errorCode);
};
var txObjectStore = tx.objectStore(TB_NAME);
for (m in json) {
var request = txObjectStore.add(json[m]);
request.onsuccess = function (e) {
console.log('adding... ' );
};
}
}
The for (var i in datastores) loop runs synchronously, updating the global TB_NAME variable every time. When the loop finishes, TB_NAME will be holding the name of the last object store.
By the time the asynchronous popTable calls run, TB_NAME will forever be holding the name of the last store, so that's the only one that will update. Try adding logging to popTable to see this.
You'll need to pass the current value of the store name along somehow (e.g. as an argument to fetchGet). Also note that although you pass popTable as a parameter when calling fetchGet you're not actually accepting it as an argument.
...
Specific changes:
Change how you call fetchGet to include the store name:
fetchGet(datastores[i].osEndpoint, popTable, datastores[i].osName);
Change the fetchGet function to accept the args:
function fetchGet(url, func, name) {
And then instead of calling popTable directly, do:
func(json, name);
And then change the definition of popTable to be:
function popTable(json, name) {
... and use name in the transaction.
I am developing my app, and one of the features will be messaging within the application. What I did, is I've developed 'send message' window, where user can send message to other user. The logic behind it is as following:
1. User A sends message to User B.
2. Firebase creates following nodes in 'Messaging':
"Messaging"->"User A"->"User B"->"Date & Time"->"UserA: Message"
"Messaging"->"User B"->"User A"->"Date & Time"->"UserA: Message"
Here is the code that I am using for sending messages:
sendMsg: function(receiver, content) {
var user = Auth.getUser();
var sender = user.facebook.id;
var receiverId = receiver;
var receiverRef = $firebase(XXX.firebase.child("Messaging").child(receiverId).child(sender).child(Date()));
var senderRef = $firebase(XXX.firebase.child("Messaging").child(sender).child(receiverId).child(Date()));
receiverRef.$set(sender,content);
senderRef.$set(sender,content);
},
(picture 1 in imgur album)
At the moment, I am trying to read the messages from the database, and sort them in according to date. What I've accomplished so far, is that I have stored the content of "Messaging/UserA/" in form of an Object. The object could be seen in the picture I've attached (picture 2).
http://imgur.com/a/3zQ0o
Code for data receiving:
getMsgs: function () {
var user = Auth.getUser();
var userId = user.facebook.id;
var messagesPath = new Firebase("https://xxx.firebaseio.com/Messaging/");
var Messages = messagesPath.child(userId);
Messages.on("value", function (snapshot) {
var messagesObj = snapshot.val();
return messagesObj;
}, function (errorObject) {
console.log("Error code: " + errorObject.code);
});
}
My question is: how can I read the object's messages? I would like to sort the according to the date, get the message and get the Id of user who has sent the message.
Thank you so much!
You seem to be falling for the asynchronous loading trap when you're reading the messages:
getMsgs: function () {
var user = Auth.getUser();
var userId = user.facebook.id;
var messagesPath = new Firebase("https://xxx.firebaseio.com/Messaging/");
var Messages = messagesPath.child(userId);
Messages.on("value", function (snapshot) {
var messagesObj = snapshot.val();
return messagesObj;
}, function (errorObject) {
console.log("Error code: " + errorObject.code);
});
}
That return statement that you have in the Messages.on("value" callback doesn't return that value to anyone.
It's often a bit easier to see what is going on, if we split the callback off into a separate function:
onMessagesChanged(snapshot) {
// when we get here, either the messages have initially loaded
// OR there has been a change in the messages
console.log('Inside on-value listener');
var messagesObj = snapshot.val();
return messagesObj;
},
getMsgs: function () {
var user = Auth.getUser();
var userId = user.facebook.id;
var messagesPath = new Firebase("https://xxx.firebaseio.com/Messaging/");
var Messages = messagesPath.child(userId);
console.log('Before adding on-value listener');
Messages.on("value", onMessagesChanged);
console.log('After adding on-value listener');
}
If you run the snippet like this, you will see that the console logs:
Before adding on-value listener
After adding on-value listener
Inside on-value listener
This is probably not what you expected and is caused by the fact that Firebase has to retrieve the messages from its servers, which could potentially take a long time. Instead of making the user wait, the browser continues executing the code and calls your so-called callback function whenever the data is available.
In the case of Firebase your function may actually be called many times, whenever a users changes or adds a message. So the output more likely will be:
Before adding on-value listener
After adding on-value listener
Inside on-value listener
Inside on-value listener
Inside on-value listener
...
Because the callback function is triggered asynchronously, you cannot return a value to the original function from it. The simplest way to work around this problem is to perform the update of your screens inside the callback. So say you want to log the messages, you'd do:
onMessagesChanged(snapshot) {
// when we get here, either the messages have initially loaded
// OR there has been a change in the messages
console.log('Inside on-value listener');
var i = 0;
snapshot.forEach(function(messageSnapshot) {
console.log((i++)+': '+messageSnapshot.val());
});
},
Note that this problem is the same no matter what API you use to access Firebase. But the different libraries handle it in different ways. For example: AngularFire shields you from a lot of these complexities, by notifying AngularJS of the data changes for you when it gets back.
Also see: Asynchronous access to an array in Firebase