I am experimenting with manipulating data in firebase and have run into the following question:
If i have 2 records inside of a subdirectory (A), and want to move them to subdirectory (B) how do i do this in javascript?
MainContainer
- A
- KEY 1 data
- KEY 2 data
- B
I am thinking copy the contents to a new record that saves to directory B and delete the directory A record, but does firebase provide an easier way to just move the record?
Firebase Realtime Database doesn't provide a move operation. You have to read the existing data, write it to the new location, then remove the data at the original location.
Referring to https://firebase.google.com/docs/database/web/read-and-write#update_specific_fields
You can update multiple nodes in a single operation. So after reading the initial data you want to manage you can set their fields to null to delete them and set the new ones to the target values
So I came across this solution it will copy the code in your old directory and recreate it to the new directory..
moveFbRecord: function(oldRef, newRef){
oldRef.once('value', function(snap) {
newRef.set( snap.val(), function(error) {
if( !error ) { }
else if( typeof(console) !== 'undefined' && console.error ) { console.error(error); }
});
});
Related
How can I listen to a specific field change with firestore js sdk ?
In the documentation, they only seem to show how to listen for the whole document, if any of the "SF" field changes, it will trigger the callback.
db.collection("cities").doc("SF")
.onSnapshot(function(doc) {
console.log("Current data: ", doc && doc.data());
});
You can't. All operations in Firestore are on an entire document.
This is also true for Cloud Functions Firestore triggers (you can only receive an entire document that's changed in some way).
If you need to narrow the scope of some data to retrieve from a document, place that in a document within a subcollection, and query for that document individually.
As Doug mentioned above, the entire document will be received in your function. However, I have created a filter function, which I named field, just to ignore document changes when those happened in fields that I am not interested in.
You can copy and use the function field linked above in your code. Example:
export const yourCloudFunction = functions.firestore
.document('/your-path')
.onUpdate(
field('foo', 'REMOVED', (change, context) => {
console.log('Will get here only if foo was removed');
}),
);
Important: The field function is not avoiding your function to be executed if changes happened in other fields, it will just ignore when the change is not what you want. If your document is too big, you should probably consider Doug's suggestion.
Listen for the document, then set a conditional on the field you're interesting in:
firebase.firestore().collection('Dictionaries').doc('Spanish').collection('Words').doc(word).collection('Pronunciations').doc('Castilian-female-IBM').onSnapshot(function(snapshot) {
if (snapshot.data().audioFiles) { // eliminates an error message
if (snapshot.data().audioFiles.length === 2) {
audioFilesReady++;
if (audioFilesReady === 3) {
$scope.showNextWord();
}
}
}
}, function(error) {
console.error(error);
});
I'm listening for a document for a voice (Castilian-female-IBM), which contains an array of audio files, in webm and mp3 formats. When both of those audio files have come back asynchronously then snapshot.data().audioFiles.length === 2. This increments a conditional. When two more voices come back (Castilian-male-IBM and Latin_American-female-IBM) then audioFilesReady === 3 and the next function $scope.showNextWord() fires.
Just out of the box what I do is watching before and after with the before and after method
const clientDataBefore = change.before.data();
console.log("Info database before ", clientDataBefore);
const clientDataAfter = change.after.data();
console.log("Info database after ", clientDataAfter );
For example now you should compare the changes for a specific field and do some actions or just return it.
Some more about before.data() and after.data() here
firebase snippit
Hello all. I am creating a web app that pulls from a firebase realtime database I have created. Using javascript I would like to pull the data from a specific node (i.e. "8").
I will then use the keys and values from the node in the web app.
What js/firebase code do I need to pull data from any specific node?
Below is the code we have tried. Long term goal is to pull data from a random node, but right now I just to find out how to pull from a specific node. Since the nodes are always going to be a number from 0-49, I don't need to use "length of array" functions when randomizing. I will use "Math.floor(Math.random() * 49" to give me a random number which I can pass into the index value for the node when I figure out how to access one specifically.
ref = firebase.database().ref('articles/');
function setupObservers() {
ref.on('value',function(snapshot){
console.log(snapshot.val())
let articleArray = []
for(key in snapshot.val()) {
let articleKeys = snapshot.val()[key]
articleArray.push(articleKeys)
}
randomArticle(articleArray)
})
}
function randomArticle(articleArray) {
let random = articleArray[Math.floor(Math.random() * articleArray.length)]
console.log(random)
}
setupObservers()
Thanks in advance!!
To read the value from a specific child node of which you know the key, you simply do:
ref = firebase.database().ref('articles');
ref.child("8").on('value',function(snapshot){
console.log(snapshot.val())
});
I need to fetch sub-set of documents in Firestore collection modified after some moment. I tried going theses ways:
It seems that native filtering can work only with some real fields in stored document - i.e. nevertheless Firestore API internally has DocumentSnapshot.getUpdateTime() I cannot use this information in my query.
I tried adding my _lastModifiedAt 'service field' via server-side firestore cloud function, but ... that updating of _lastModifiedAt causes recursive invocation of the onWrite() function. I.e. is does also not work as needed (recursion finally stops with Error: quota exceeded (Function invocations : per 100 seconds)).
Are there other ideas how to filter collection by 'lastModifiedTime'?
Here is my 'cloud function' for reference
It would work if I could identify who is modifying the document, i.e. ignore own updates of _lastModified field, but I see no way to check for this
_lastModifiedBy is set to null because of current inability of Firestore to provide auth information (see here)
exports.updateLastModifiedBy = functions.firestore.document('/{collId}/{documentId}').onWrite(event => {
console.log(event.data.data());
var lastModified = {
_lastModifiedBy: null,
_lastModifiedAt: now
}
return event.data.ref.set(lastModified, {merge: true});
});
I've found the way to prevent recursion while updating '_lastModifiedAt'.
Note: this will not work reliably if client can also update '_lastModifiedAt'. It does not matter much in my environment, but in general case I think writing to '_lastModifiedAt' should be allowed only to service accounts.
exports.updateLastModifiedBy = functions.firestore.document('/{collId}/{documentId}').onWrite(event => {
var doc = event.data.data();
var prevDoc = event.data.previous.data();
if( doc && prevDoc && (doc._lastModifiedAt != prevDoc._lastModifiedAt) )
// this is my own change
return 0;
var lastModified = getLastModified(event);
return event.data.ref.set(lastModified, {merge: true});
});
Update: Warning - updating lastModified in onWrite() event causes infinite recursion when trying to delete all documents in Firebase console. This happens because onWrite() is also triggered for delete and writing lastModified into deleted document actually resurrects it. That document propagates back into console and is tried to be deleted once again, indefinitely (until WEB page is closed).
To fix that issue above mentioned code has to be specified individually for onCreate() and onUpdate().
How about letting the client write the timestamp with FieldValue.serverTimestamp() and then validate that the value written is equal to time in security rules?
Also see Mike's answer here for an example: Firestore Security Rules: If timestamp (FieldValue.serverTimestamp) equals now
You could try the following function, which will not update the _lastModifiedAt if it has been marked as modified within the last 5 seconds. This should ensure that this function only runs once, per update (as long as you don't update more than once in 5 seconds).
exports.updateLastModifiedBy = functions.firestore.document('/{collId}/{documentId}').onWrite(event => {
console.log(event.data.data());
if ((Date.now() - 5000) < event.data.data()._lastModifiedAt) {return null};
var lastModified = {
_lastModifiedBy: null,
_lastModifiedAt: now
}
return event.data.ref.set(lastModified, {merge: true});
});
I wrote a script that allows you to delete a property in the caches of the application, however I need to run this script only once when I install the application.
someone has an idea, thanks
var executed = 0;
if(executed === 0){
Ti.App.Properties.removeProperty("My_Property");
executed++;
}
The only ways you can hold some value across app sessions are Ti.App.Properties or sql database. So you can do it in two ways as below:
Solution 1: Use another property to know that you have deleted the desired property.
// for first time installation, the default value (or 2nd parameter) will be false as you have not deleted the property yet
var isDeleted = Ti.App.Properties.getBool('My_Property_Deleted', false);
if (isDeleted) {
Ti.App.Properties.removeProperty("My_Property");
// since you have deleted it, now set it to true so this 'if' block doesn't runs on any next app session
Ti.App.Properties.setBool('My_Property_Deleted', true);
} else {
// you have already deleted the property, 'if' block won't run now
}
Solution 2: Create a new database or pre-load a shipped db with your app.
// Titanium will create it if it doesn't exists, or return a reference to it if it exists (after first call & after app install)
var db = Ti.Database.open('your_db');
// create a new table to store properties states
db.execute('CREATE TABLE IF NOT EXISTS deletedProperties(id INTEGER PRIMARY KEY, property_name TEXT);');
// query the database to know if it contains any row with the desired property name
var result = db.execute('select * from deletedProperties where name=?', "My_Property");
if (result.rowCount == 0) { // means no property exists with such name
// first delete the desired property
Ti.App.Properties.removeProperty("My_Property");
// insert this property name in table so it can be available to let you know you have deleted the desired property
db.execute('insert into deletedProperties(name) values(?)', "My_Property");
} else {
// you have already deleted the property, 'if' block won't run now
}
// never forget to close the database after no use of it
db.close();
There can be other ways as well, but these 2 will work for what you want. Read more about Ti.Database here
I've been playing around with http://almende.github.com/chap-links-library/timeline.html which allows the user to add/edit/delete events on the timeline. Closing or refreshing the browser resets it to the pre-loaded data source - JSON, table info or Google Spreadsheet. Nothing the user adds or changes is saved.
How do you make user changes persistent?
I've used HTML5 localStorage before for saving text, checkbox, and select box entries, etc. but with this Timeline the only entry is:
div id="mytimeline"
which has a script associated with it:
// Instantiate our timeline object.
timeline = new links.Timeline(document.getElementById('mytimeline'));
which is the reference to the JS that builds the timeline container.
Any ideas or examples or pointers?
Thanks.
Update:
Here is what I have so far:
//Check to see if localStorage is supported
var db = getLocalStorage() || alert("Local Storage Not supported in this browser. Try updating to the latest Firefox, Chrome or Safari browsers.");
function getLocalStorage() {
try {
if(window.localStorage ) return window.localStorage;
}
catch (e)
{
return undefined;
}
}
//Store Timeline Data to localStorage
function storeTimelineData(){
var data=timeline.getData();
localStorage.setItem('mytimeline', JSON.stringify(data));
var storedData=JSON.parse( localStorage.getItem('myTimeline') );
// clear storage
function clearLocal() {
clear: localStorage.clear();
return false;
}
I've also made these changes - body onload="storedData()" to try to load localStorage saved values and changed div id="mytimeline" onmouseup="storeTimelineData()" to store the values when changes are made to the timeline.
Changes to the Timeline are being saved in localStorage and I can see these changes in the console for Key/Values. When I refresh the browser though, these are not being loaded into mytimeline. What did I miss?
Thanks.
I've never seen plugin until your post but in the API docs are all sorts of methods. The most important one you would need to start would be getData().
Simplest storage scenario would be to set up a timed interval to get the data , convert it to JSON and store it. Alternative would be to update your stored data every time use interacts with events.
A basic storage update function would be along the lines of:
function storeTimelineData(){
var data=timeline.getData();
localStorage.setItem('myTimeline', JSON.stringify(data));
}
Then when page loads you would need to check if there is data in localStorage , convert it to a javascript object using :
var storedData= JSON.parse( localStorage.getItem('myTimeline') );
And use this data to initialize the plugin if the data exists.
I have really just given you a basic overview. There are numerous details you will have to sort out from here