I am creating an application using Firebase Firestore and Plugin.CloudFirestore for Xamarin Forms based off of the Sample Project posted on the plugin's GitHub (link:
https://github.com/f-miyu/Plugin.CloudFirestore).
I am trying to learn how to write Async Reactive Commands based off of how they are written in the sample project but I'm having a really hard time reverse engineering this code.
UpdateCommand = new[] {
_todoItem.Select(x => x == null),
Name.Select(x => string.IsNullOrEmpty(x))
}.CombineLatestValuesAreAllFalse()
.ObserveOn(SynchronizationContext.Current)
.ToAsyncReactiveCommand();
UpdateCommand.Subscribe(async () =>
{
var todoItem = _todoItem.Value;
todoItem.Name = Name.Value;
todoItem.Notes = Notes.Value;
_ = CrossCloudFirestore.Current.Instance.Document($"{TodoItem.CollectionPath}/{todoItem.Id}")
.UpdateAsync(todoItem)
.ContinueWith(t =>
{
System.Diagnostics.Debug.WriteLine(t.Exception);
}, TaskContinuationOptions.OnlyOnFaulted);
await navigationService.GoBackAsync();
});
This code snippet is from the "TodoItemDetailPageViewModel.cs" file within the sample project if you would like more context.
The code above updates the field values of the document that is selected from the main page via the Firestore API. The code is working but I don't have any idea what the above code means and how the command works. Could someone break it down for me and explain what is going on? I am sure someone else could benefit as well.
Thanks
Related
I am working on react native application I use firebase as my backend. I fetch data from firebase real time database and render it on the page. But now I want my application to be supported offline.
I used following two functions for rendering.
For listings from database
const loadListings = () => {
let data = [];
listingRef.orderByChild("created_at").on("value", (snapshot) => {
data = [];
snapshot.forEach((listing) => {
data.push(listing.val());
});
cache.store("listings", data.slice(0, 10)); // only stores latest ten listings
setListings(data);
setLoading(false);
});
};
and then use it inside useEffect like.
useEffect(() => {
loadListings();
}, []);
and for listings from cache I used this.
const loadListingsCached = async () => {
let data = await cache.get("listings");
setListings(data);
};
Now I cant put a check inside firs function as effect hook will run only one time and initialy network status is null. its not defined.
how do I achieve this?
by the way link to package I used for detecting connectivity
Edit
I used this hook as second argument to useEffect() but didn't work for me
const netInfo = useNetInfo();
I
What you want to achieve is make the code different depending on what is the network status. In the answer linked by #Rohit there is my answer about how to check the network connectivity with Net Info Package.
What you have to do is make the effect dependant on the status change. You should pass it as a argument to the effect.
const netInfo = useNetInfo();
useEffect(() => {
loadListings();
}, [netInfo]);
This way the code will always run when a network change is detected. I hope this is what you wanted to achive. Please be more specific about you goal and what is the problem. Current questions does not specify if the hook is not working, or the rendering function does not trigger etc.
I'm trying to set the Custom time attribute in firebase on the front end. Everything is possible to set, like contentDisposition, custom Metadata etc, just can't find any way or any info about setting Custom time.
You can see it referenced here https://cloud.google.com/storage/docs/metadata#custom-time
You can set the custom time on the file manually in the Storage cloud console, but even when you do and you load the file in firebase on the front end, it's missing from the returned object! (makes me feel like it's not possible to achieve this)
var storage = this.$firebase.app().storage("gs://my-files");
var storage2 = storage.ref().child(this.file);
//// Tried this
var md = {
customTime: now.$firebase.firestore.FieldValue.serverTimestamp()
};
//// & Tried this
var md = {
Custom-Time: now.$firebase.firestore.FieldValue.serverTimestamp()
};
storage2.updateMetadata(md).then((metadata) => {
console.log(metadata);
}).catch((err) => {
console.log(err);
});
The reason I ask is I'm trying to push back the lifecycle delete date (which will be based on the custom time) every time the file is loaded. Does anyone know the answer or an alternative way of doing it?
Thanks in advance
The CustomTime metadata is not possible to update using Firebase JavaScript SDK since it is not included in the file metadata properties list mentioned in the documentation. So even if you specify it as customTime: or Custom-Time: the updateMetadata() method does not perform any changes.
I suggest you as a better practice, set the CustomTime metadata from the cloud console and modify the CustomTimeBefore Lifecycle condition from the back-end each time you load the file using the addLifeCycleRule method of the GCP Node.js Client.
// Imports the Google Cloud client library
const {Storage} = require('#google-cloud/storage');
// Creates a client
const storage = new Storage();
//Imports your Google Cloud Storage bucket
const myBucket = storage.bucket('my_bucket');
//-
// Delete object that has a customTime before 2021-05-25.
//-
myBucket.addLifecycleRule({
action: 'delete',
condition: {
customTimeBefore: new Date('2021-05-25')
}
}, function(err, apiResponse) {});
I am new to Polymer and I am stuck on setting the database data. I manged to make email authentication work and I need to save user data after user creation. I initialize the app with firebase-app element.
Here is the important part:
this.$.auth.createUserWithEmailAndPassword(email, pass).then(function (user) {
user.sendEmailVerification();
document.getElementById("emaildialog").toggle();
var view = document.getElementById("r_view");
firebase.database().ref('/user/' + user['uid']).set({
name: view.name,
surname: view.surName
}).catch(function (err) {
console.log(err.message);
});
})
User is successfully created but the user data won't get saved and
firebase.database is not a function"
error is thrown. I guess it's because I don't have access to firebase.database function in the scope. I found many ways how to solve the issue using pure JavaScript, but I'm not sure what is the official "Polymer way".
EDIT:
I still can't get it to work. i managed to get a reference of app object but it seems like there is no database method available. I wrote a simple function for debugging:
debugFunction: function () {
if (!!this.user) {
var fb = this.$.auth.app;
console.log(!!fb); // Output is true,
var database = fb.database();
}
}
I get the "Uncaught TypeError: fb.database is not a function(…)" once more.
Thanks in advance, Jan
You can get the reference of the firebase app inside your firebase-auth element. Make sure you do this outside of the callback function so you won't have to deal with getting the proper scope of this. If you must, you can do .bind or arrow functions.
var app = this.$.auth.app;
Then after that you can do app.database() as a replacement for the firebase one.
I'm learning Meteor and I was trying to pass the result of a Collection.find() into and array (using a variable) and the simpler code I have is (in a file that is in the root):
CalEvents = new Mongo.Collection('calevents'); //creating a collection
/*------------------------- Populating the database with dummy data-------*/
if (Meteor.isServer) {
Meteor.startup(function () {
if (CalEvents.find().count() === 0) {
CalEvents.insert({
title: "Initial room",
start: '2010-02-02'
});
}
});
}
/*--------------- Creating an array from the collection-----------------*/
events = [];
calEvents = CalEvents.find({});
calEvents.forEach(function(evt){
events.push({
title: evt.title,
start: evt.start,
})
});
The page has nothing to show but using the console I can see (CalEvents.find().fetch()) that I have data in my database but the "events" variable is empty...
I can't understand why because I tried several other things such as changing file names and moving code to guarantee the proper order.
And I already tried to use CalEvents.find().fetch() to create an array an put the result into a variable but I'm not able to do it...
Does anyone know what's so simple that I'm missing?...
Do you use autosubscribe?
You probably need to make sure the sbscription is ready. See Meteor: How can I tell when the database is ready? and Displaying loader while meteor collection loads.
The reason you do see CalEvents.find().fetch() returning items in the console is that by the time you make that call, the subscription is ready. But in your events = []; ... code (which I assume is in a file under the client directory, you might have assumed that the subscription data has arrived when in fact it has not.
A useful debugging tool is Chrome's device mode ("phone" icon near the search icon in DevTools), which lets you simulate slow networks (e.g. GPRS, with 500ms delay for every request).
I have a basic POCO (No database) structure implementing an OData Service with the latest WebAPI update. Unfortunately, the latest update broke the HasNavigationPropertiesLink code that I had to generate links which can be used for $expand operations. Here is my old code:
var jobs = modelBuilder.EntitySet<Job>("Jobs");
jobs.EntityType.NavigationProperties,
(entityContext, navigationProperty) => new
Uri(entityContext.UrlHelper.Link(ODataRouteNames.PropertyNavigation,
new
{
Controller = "Jobs",
parentId = entityContext.EntityInstance.ID,
NavigationProperty = navigationProperty.Name
})));
And here is my new code (that doesn't work):
var jobs = modelBuilder.EntitySet<Job>("Jobs");
jobs.EntityType.NavigationProperties,
(entityContext, navigationProperty) => new
Uri(entityContext.Url.Link(<??WHAT GOES HERE??>,
new
{
Controller = "Jobs",
parentId = entityContext.EdmObject,
NavigationProperty = navigationProperty.Name
})),
true);
Any help is much appreciated - this doesn't seem to have been documented in the updates.
looks like the version of the OData bits you are using is very old. In our current version, you can use the ODataConventionsModelBuilder to create a model that defines navigation properties and links following conventions, so unless you need to generate custom links, it's a better way to go. However, if you want to generate a custom navigation link, the link generation code looks something similar to this:
var jobs = builder.EntitySet<Job>("Jobs");
jobs.HasNavigationPropertiesLink(customers.EntityType.NavigationProperties,
(context, navigationProperty) =>
{
var result = "http://mydomain.com/prefix/odataPath";
//In order to generate this link you can use context.Url.ODataLink(new EntityPathSegment("Jobs"), ...);
return new Uri(result);
}, followsConventions: true);
it is better to use ODataConventionsModelBuilder as Javier has suggested. But if you still want to set up your own odata model you can do it:
var jobs = builder.EntitySet<Job>("Jobs");
jobs.HasNavigationPropertiesLink(customers.EntityType.NavigationProperties,
(context, navigationProperty) => context.GenerateNavigationPropertyLink(navigationProperty, false)
, followsConventions: true);