I'm using Polkadot.js in my project, and I have a function where user click to filter assets by categories. The issue is if the user click very fast, two rpc calls will be dispatched, instead of the later call overriding the first call, this will result in getting duplicate results.
Is there any way I can either cancel the first inflight rpc call, or let the second call overrides the first one? They share the same method name and the later one will have a higher id.
Any suggestions or help is much appreciated!
Related
We have a case where we only want one HTTP request to go out at a time and only want to allow retry or call again if the pending call either succeeds or fails. We've been doing the classic wrap it in a boolean but were wondering if there was an operator for it. My hunch is no.
I think you would need switchMap. It will only subscribe to the last value of the external observable and it will map it to an internal observable. With switchMap, its possible to cancel previous http requests on the fly.
For more info take a look in the following link
I have a template in which a user should be able to click on a button to bring up a modal and in the modal choose a handful of items out of a list of about 10,000 items which are displayed there to search or scroll through.
Since this collection is so big, I don't want to keep it around in memory when I don't absolutely need it.
So I would like to subscribe to this collection only when the modal is being viewed and I would like to ensure that I am unsubscribed if the modal is not being viewed.
Is there a way to explicitly unsubscribe from a collection?
There are a couple of ways you can do this:
Use the subscription handle
subscribe returns a handle you can call stop on. For example:
var handle = Meteor.subscribe('stuff');
handle.stop();
Use an autorun
Because an autorun will automatically start and stop subscriptions when its reactive dependencies change, this will work:
Tracker.autorun(function () {
if (Session.get('showingModal'))
Meteor.subscribe('stuff');
});
Side note - it may make more sense to use a method call for searching such a large data set rather than publishing the entire thing to the client. For example you can set a session variable whenever the user's query changes, then use an autorun to update the result set based on the method's return value.
https://docs.meteor.com/#/full/meteor_subscribe
Quoting the docs :
Meteor.subscribe returns a subscription handle, which is an object
with the following methods:
stop() Cancel the subscription. This will typically result in the
server directing the client to remove the subscription's data from the
client's cache.
So basically what you need to do is storing the subscription handle in a variable and call the stop method when you don't need those published documents anymore.
Note that if you're using iron:router (and you probably should), this is taken care of automatically for you on each route change, which is convenient but has the side effect of provoking a lot of sometimes unnecessary calls to Meteor.publish calls which are non trivial for the server and bandwidth... to address this matter you can use meteorhacks:subs-manager but it's another topic anyway.
I would like to abort the deletion of an object (A custom Content-Type), and redirect to a page (a view) that sets the workflow to a custom state named Unavailable, shows a message to the user "You succesfully deleted the object!". The object will still be on ZODB, but for some groups it'll simply not be seen, as if it was really deleted.
I can do a raise in a subscriber using IObjectWillBeRemovedEvent, but trying to use raise zExceptions.Redirect("url") doesn't work. The raise call avoids the deletion, but a message "The object could not be deleted" is shown instead of the redirection.
Anyone has a solution to this scenario?
As you can see Plone / Zope 2 object management is messy (yes, I am willing to burn karma just to say this). You need to override delete action in the user interface level, not on the object level.
Try to figure out how to customize delete actions in Plone user interface.
Make sure the default Delete actions is no longer visible and available (e.g. set higher needed permission for it e.g. cmf.ManagePortal)
Create another Delete action which goes according to your specialized workflow
I believe Delete can be configured from portal_actions, but there might be separate cases for deleting one object (Actions menu) and deleting multiple objects (folder_contents).
You need REQUEST.response.redirect("url"). I'm pretty sure that zExceptions.Redirect is the way that Zope internally handles response.redirect() calls. Be sure you still raise another exception after calling redirect() so that the transaction is aborte.
That said, this sure seems like the wrong way to accomplish this. For one thing, you'll do at least double indexing, which is done before the transaction aborts. Catalog indexing is the most expensive part of processing a request that modifies content so this creates wasteful load on your server.
Events are for doing additional stuff which is only tangentially related to the event. What you want is to fundamentally change what happens when someone deletes. Maybe you should patch/override the underlying deletion method on the container objects (folders?) to do your worklfow transition.
You could raise a OFS.ObjectManager.BeforeDeleteException in the event handler to stop the deletion. If you raise a LinkIntegrityNotificationException you get redirected to Plones nice Link intergrity page.
from OFS.interfaces import IObjectWillBeRemovedEvent
from plone.app.linkintegrity.exceptions import LinkIntegrityNotificationException
import grok
#grok.subscribe(ICSRDocument, IObjectWillBeRemovedEvent)
def document_willbemoved(doc, event):
raise LinkIntegrityNotificationException(doc)
I'm writing a wizard UI based on the QWizard Qt object. There's one particular situation where I want the user to log in to a service using host, username, and password. The rest of the wizard then manipulates this service to do various setup tasks. The login may take a while, especially in error cases where the DNS name takes a long time to resolve -- or perhaps it may not even resolve at all.
So my idea is to make all three fields mandatory using the registerField mechanism, and when the user hits Next, we show a little throbber on the wizard page saying "Connecting to server, please wait..." while we try to connect in the background. If the connection succeeds, we advance to the next page. If not, we highlight the offending field and ask the user to try again.
However, I'm at a loss for how to accomplish this. The options I've thought of:
1) Override validatePage and have it start a thread in the background. Enter a wait inside validatePage() that pumps the Qt event loop until the thread finishes. You'd think this was the ugliest solution, but...
2) Hide the real Next button and add a custom Next button that, when clicked, dispatches my long running function in a thread and waits for a 'validation complete' signal to be raised by something. When that happens, we manually call QWizard::next() (and we completely bypass the real validation logic from validatePage and friends.) This is even uglier, but moves the ugliness to a different level that may make development easier.
Surely there's a better way?
It's not as visually appealing, but you could add a connecting page, and move to that page. If the connection succeeds, call next() on the wizard, and if the connection fails, call previous() and highlight the appropriate fields. It has the advantage of being relatively straightforward to code.
My final choice was #2 (override the Next button, simulate its behavior, but capture its click events manually and do the things I want to with it.) Writing the glue to define the Next button's behavior was minimal, and I was able to subclass QWizardPage with a number of hooks that let me run my task ON the same page, instead of having to switch to an interstitial page and worry about whether to go forwards or backwards. Thanks Caleb for your answer though.
I know this has already been answered (a long time ago!) but in case anyone else is having the same challenge. Another method for this is to create a QLineEdit, initiate it as empty and set it as a mandatory registered field. This will mean that "Next" is not enabled until it is filled with some text.
Run your connection task as normal and when it completes use setText to update the QLineEdit to "True" or "Logged in" or anything other than empty. This will then mean the built in isComplete function will be passed as this previously missing mandatory field is now complete. If you never add it to the layout then it won't be seen and the user won't be able to interact with it.
As an example ...
self.validated_field = QLineEdit("")
self.registerField('validated*', self.validated_field)
and then when your login process completes successfully
self.validated_field.setText("True")
This should do it and is very lightweight. Be sure though that you consider the scenario where a user then goes back to that page and whether you need to reset the field to blank. If that's the case then just add in the initialisePage() function to set it back to blank
self.validated_field.setText("")
Thinking about it you could also add the line edit to the display and disable it so that a user cannot update it and then give it a meaningful completion message to act as a status update...
self.validated_field = QLineEdit("")
self.validated_field.setDisabled(True)
self.validated_field.setStyleSheet("border:0;background-color:none")
self.main_layout.addWidget(self.validated_field)
self.registerField('validated*', self.validated_field)
and then when you update it..
self.validated_field.setText("Logged in")
Is there any way to make multiple requests to the callback function in asp.net when using the ICallbackEventHandler? I need the results for each result, however, when I iterate through and call the function, I get the result only for the last call. Any way to make it return a result for each call?
This is what I am passing in via javascript:
function NoPostback() {
$(".spans").each(function(index, item) {
CallServer($(item).attr("myattr"));
});
}
In this, myattr is a custom attribute that holds a value (1..10). What I want returned is something like ('you said: ' + id) to be returned for each of the calls, so that I can go ahead and place them in the appropriate holders.
However, only one item is returned which is the final call made. For instance if there are 4 items, it returns only ('you said: 4').
Any idea on how to have all of them returned?
Thanks in advance.
Most Javascript AJAX frameworks either abort any subsequent requests if one is in progress, or they ignore previous requests and only handle the latest. The AJAX request itself will pass through the browser's XmlHttpRequest object, but the rest of the javascript code is running within the pages thread. Currently, there is no concurrent programming with javascript (however this is slated to change.)