I have some general questions, I start of on page main.ts
Via onInit I am grabbing data from a mongoose database server, which I save in an array.
This array needs to be available in other components. The way I do this right now, which seems to work, by using a service.ts
In the service I have a lot BehaviorSubjects and Subjects. So whenever I get the array data from mongoose I send a message to the service, and the other components subscribe to that message.
I am sometimes using Subject instead of BehaviorSubject because it throws error messages as in HTML I am using *ngFor and it expects an array, not a string 'default message'.
I am just wondering if this is a correct setup to move data between pages.
Right now I am also using this message system for updates on my component.
So if someone makes a comment or post on my website I send a message to my service which in turn updates an observable and my component subscribes again to that.
Are there better ways to update my site for new data and is there an easy way to explain why sometimes I get this error message from *ngFor and in other cases it doesn't throw this error whilst still using *ngFor.
i.e. when I update an observable will the component receive the message straight away or will it receive onInit.
With that also the question if it is best practice to use the below in the constructor of the component or the onInit.
I unsubscribe OnDestroy.
this.newService.currentMessageComment
.takeWhile(() => this.alive)
.subscribe(message => {
service.ts
public messageSourceMarketCap = new BehaviorSubject<any>('default message');
currentMessageMarketCap = this.messageSourceMarketCap.asObservable();
public messageSourceHistory = new Subject<any>();
currentMessageHistory = this.messageSourceHistory.asObservable();
public messageSouceApi = new BehaviorSubject<any>('default message');
currentMessageApi = this.messageSouceApi.asObservable();
public messageSourceBody = new BehaviorSubject<any>('default message');
currentMessageBody = this.messageSourceBody.asObservable();
Why are you using BehaviouSubject. I think in your case Subject will be better. BehaviouSubject fits in case when you want to pass a initial value while creating observable.
You can also quick fix by emiting an empty array as ngFor expects an array. Change from "default message" to [].
Hope it will help
Related
Is it possible to get document back after adding it / updating it without additional network calls with Firestore, similar to MongoDB?
I find it stupid to first make a call to add / update a document and then make an additional call to get it.
As you have probably seen in the documentation of the Node.js (and Javascript) SDKs, this is not possible, neither with the methods of a DocumentReference nor with the one of a CollectionReference.
More precisely, the set() and update() methods of a DocumentReference both return a Promise containing void, while the CollectionReference's add() method returns a Promise containing a DocumentReference.
Side Note (in line with answer from darrinm below): It is interesting to note that with the Firestore REST API, when you create a document, you get back (i.e. through the API endpoint response) a Document object.
When you add a document to Cloud Firestore, the server can affect the data that is stored. A few ways this may happen:
If your data contains a marker for a server-side timestamp, the server will expand that marker into the actual timestamp.
Your data data is not permitted according to your server-side security rules, the server will reject the write operation.
Since the server affects the contents of the Document, the client can't simply return the data that it already has as the new document. If you just want to show the data that you sent to the server in your client, you can of course do so by simply reusing the object you passed into setData(...)/addDocument(data: ...).
This appears to be an arbitrary limitation of the the Firestore Javascript API. The Firestore REST API returns the updated document on the same call.
https://firebase.google.com/docs/firestore/reference/rest/v1beta1/projects.databases.documents/patch
I did this to get the ID of a new Document created, and then use it in something else.
Future<DocumentReference<Object>> addNewData() async {
final FirebaseFirestore _firestore = FirebaseFirestore.instance;
final CollectionReference _userCollection = _firestore.collection('users');
return await _userCollection
.add({ 'data': 'value' })
.whenComplete(() => {
// Show good notification
})
.catchError((e) {
// Show Bad notification
});
}
And here I obtain the ID:
await addNewData()
.then((document) async {
// Get ID
print('ID Document Created ${document.id}');
});
I hope it helps.
Android :
What I've implemented till now is, get spinner value to the immediate subscriber using itemSelection().
Code :
Observavle observavle = RxAdapterView.itemSelections(spinner);
observable.subscribeOn(AndroidSchedulers.mainThread())
.subscribe(integer -> {
Log.v("spinner", integer.toString());
});
What I want to achieve is :
I want to subscribe multiple observers to this Observable.
For which I have created few Observers and used
Observable.subscribe(observer1);
Observable.subscribe(observer2);
Observable.subscribe(few more observers);
To get spinner updated value on these observers, but this is not working,
OnNext() of these observers won't get called on spinner value change.
(Note: This situation works perfectly in case of RxBinding Textview using on textchange() ).
Will surely upvote if you can help me with this.
You can use the share() operator:
Observavle observavle = RxAdapterView.itemSelections(spinner).share();
You can read more about share() in this blog post.
I'm using node-wit to develop a chatbot application.
This is working fine mostly, but I've run into a problem with the use of the context.
I'm using the runActions api :
this.witClient.runActions(customer._key, messageText, witContext).then((newContext => {}
)).catch(reject);
I have defined a number of actions, which set the context.
This is working fine, as long the context is taking place over one message.
For example, if I were to call an action called addProduct :
addProduct({sessionId, context, text, entities}) {
return new Promise((resolve, reject) => {
context.product = `myNewProduct';
resolve(context);
});
},
It will then show a message using the 'product' context key.
However, when I try to use it over 2 messages, it seems to have lost the context ( for example, when asking a multiple choice question, and then handling that response ).
If I understand how it's working correctly, then node-wit doesn't keep the context beyond messages ( I assumed this at first because I'm passing a session key ).
A solution I see is to store the resulting context ( newContext in this case) in a session/user specific way, and then restore it and pass it again when the user is sending his new message.
Meaning, something like this :
witContext = getContextFromSession();
this.witClient.runActions(customer._key, messageText, witContext).then((newContext => { setContextInSession(newContext) }
)).catch(reject);
Would this be the correct way of handling it ?
Off course you have to store your context state, you decide how to store it. But, take into account what is the most efficient way if you're gonna have a lot of users, and your reasources available.
As you can see in the official example for nodeJs, there's a method named findOrCreateSession on https://github.com/wit-ai/node-wit/blob/master/examples/messenger.js they get the session before the wit actions are called.
In my particular case, I am storing it in the database, so I get the session before the action is called, so I can send the context, then in the actions I query the session again to modify the resulting context and store it again, try the best implementation for your needs.
Related question: Web API action parameter is intermittently null and http://social.msdn.microsoft.com/Forums/vstudio/en-US/25753b53-95b3-4252-b034-7e086341ad20/web-api-action-parameter-is-intermittently-null
Hi!
I'm creating a ActionFilterAttribute in ASP.Net MVC WebAPI 4 so I can apply the attribute in action methods at the controller that we need validation of a token before execute it as the following code:
public class TokenValidationAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext filterContext)
{
//Tried this way
var result = string.Empty;
filterContext.Request.Content.ReadAsStringAsync().ContinueWith((r)=> content = r.Result);
//And this
var result = filterContext.Request.Content.ReadAsStringAsync().Result;
//And this
var bytes = await request.Content.ReadAsByteArrayAsync().Result;
var str = System.Text.Encoding.UTF8.GetString(bytes);
//omit the other code that use this string below here for simplicity
}
}
I'm trying to read the content as string. Tried the 3 ways as stated in this code, and all of them return empty. I know that in WebApi I can read only once the body content of the request, so I'm commenting everything else in the code, and trying to get it run to see if I'm getting a result. The point is, the client and even the Fiddler, reports the 315 of the content length of the request. The same size is getting on the server content header as well but, when we try read the content, it is empty.
If I remove the attribute and make the same request, the controller is called well, and the deserialization of Json happens flawless. If I put the attribute, all I get is a empty string from the content. It happens ALWAYS. Not intermittent as the related questions state.
What am I doing wrong? Keep in mind that I'm using ActionFilter instead of DelegatingHandler because only selected actions requires the token validation prior to execution.
Thanks for help! I really appreciate it.
Regards...
Gutemberg
By default the buffer policy for Web Host(IIS) scenarios is that the incoming request's stream is always buffered. You can take a look at System.Web.Http.WebHost.WebHostBufferPolicySelector. Now as you have figured, Web Api's formatters will consume the stream and will not try to rewind it back. This is on purpose because one could change the buffer policy to make the incoming request's stream to be non-buffered in which case the rewinding would fail.
So in your case, since you know that the request is going to be always buffered, you could get hold of the incoming stream like below and rewind it.
Stream reqStream = await request.Content.ReadAsStreamAsync();
if(reqStream.CanSeek)
{
reqStream.Position = 0;
}
//now try to read the content as string
string data = await request.Content.ReadAsStringAsync();
I'm using ajax requests to get one of PartialViews in my project. I want to pass a message by INotifier.
Cuttently i'm using HttpStatusCodeResult return new HttpStatusCodeResult(204, "Message");to pass informations about the errors but is not satisfying solution.
$(this).load($(this).attr("href"), function (response, status, xhr) {
if (xhr.status == 204) {
// show message
}
});
I'm wondering that is possible by using standard INotifier.Error() in ActionResult.
Nope. The default notifier is not suitable for AJAX requests. What it does, it queues notifications inside a temporary collection. Queued notifications are then written to the client when request ends - pushed into Layout.Messages zone.
In your case it would be best to implement your own INotifier that would follow the required logic. It's a very simple interface to implement so it's not actually that much work.
I needn't to implement INotifier, i only placed in my PartialView this:
#Display(WorkContext.Layout.Zones["Messages"])
Now the message isn't rendered in main zone (in Layout.cshtml of used theme), but could be placed anywhere in your PartialView, for example under the affected table.