I have one query which is bit complex for me to explain but do ask me if you need any further details...
Angular version: 8.
Subject : issue while Switching components is circular.
Like from Component A. -> B -> A -> B
Brief details of my problem
From 'A' component I have selected couple of employees then click on the apply filter button so that I can switch to B component.
On every employees check-box clicked emitting event using service so that from 'B' component I should be able to fetch those selected employees and do further logic (like. API call)
Switching from A to B is working as expected because based on selected employees I am hitting the API to get their details.
But to reset the selected employees I am redirecting back to A component so that I can add more or remove employees...
Now the problem what I was facing is
As I have logic in component B, to hit the API and get the employees details.
The problem is after one round back from component 'B' on every selection one hit goes to API to get updated emp details.
I know it's happening bcz of EvenEmitter but what is the best possible solution for this so that on every event emit it should not make API call from 'A' untill and untill I am not in component B.
I have fixed my problem.. every time when we redirect to other route it will automatically call the ngOnDestroy where you can unsubscribe all the services that you have subscribed.
Syntax to unsubscribe:
Declare one property
ServiceSubscriptions: Subscription;
ngOnDestroy() {
this.ServiceSubscriptions.unsubscribe();
debugger;
}
Feel free to ask me if anybody has any query.
Related
Problem
Actions in my redux store are appearing to log-jam behind one another. I'm iterating through a set of thunks, which each call a number of actions to show they've started, succeeded, etc. When this happens, an action appears for a second in redux dev tools, then is erased.
If I post another action, then all the actions appear all at once, like container ships following the ever-given.
Link to gif of the issue
In this gif I connect to a testing database, afterwards, a number of operations dispatch. I can see those operations in the console, but not devTools. Then, I post another action via the onscreen button, and all the actions flow through at once.
I'm hunting for instances of mutated state, but all reducers destructure state into a new object via:
let newState = {...state}
Any tips?
EDIT:
When I dispatch the same operation from behind a button element, it works just fine. The code that's log jamming is being called by an event listener attached to an event emitter... maybe this has something to do with it?
After debugging, I've traced the problem back to the redux replaceReducer method. I call it 3 times in this sequence. The first and second invocation works fine, but on the third - the store stops receiving actions.
store.injectReducer = (key, asyncReducer) => {
storeTools.dispatchAction({type:"STORE_INJECT_REDUCER_" + key})
store.asyncReducers[key] = asyncReducer;
let combinedReducers = createReducer(store.asyncReducers);
storeTools.dispatchAction({type:"STORE_INJECT_REDUCER_" + key})
store.replaceReducer(combinedReducers);
storeTools.dispatchAction({type:"RESET"})
console.log("replaceReducer")
}
^^^
This code prints actions on the first 2 invocations, but on the third, it prints the first two actions, but not the third.
This bug was caused by invoking "replaceReducer" multiple times within the same thread. From what I now understand - if you call replaceReducer in a forEach loop... you're gunna have a bad time.
My solution was to create a function that stages multiple reducers - then calls replaceReducer once.
May folks from the future benefit from this knowledge.
I have a query that is observed on viewWillAppear on View Controller A
let query = FIRDatabase.database().reference().child("tags").
queryOrdered(byChild: "users/uid").queryEqual(toValue: userId)
In the same view controller, in viewDidDisappear I remove this observer.
So let's say I push into another view controller from View Controller A.
When I come back to View Controller A, the observer returns a snapshot, even though my data on the backend hasn't changed.
I only want a snapshot returning if there's been some actual change to my database. How do I solve this problem? Thanks.
One answer is to simply let the observer do it's job and update your data in the background.
So if the user is on controllerA the observer updates a datasource (an array) so then the UI is updated from that array.
When the user switches to controllerB, the observer can still update the array, but don't update the UI in controllerA since there's no need to.
When the user switches back to A you'll have current data available so just reload the tableView (assuming iOS here) from the array.
This solution reduces the 'polling' nature and let's Firebase do the heavy lifting to notify your app when it needs to. You're just reloading the tableViews from an array when that controller becomes active.
Edit
The idea here is to add the observer once - perhaps when the view loads the first time only (viewDidLoad) or maybe in your app delegate. Once you add the observer it will update your dataSource arrays when data changes so when you move from view to view the only action needed will be to reload the tableView from the updated array.
There are times when you may want to remove an observer but it doesn't sound like you need to do that from your question. So - attach the observers once and let them update the dataSource arrays as the data changes. Reload your tableViews when switching views.
You have put the query in viewWillAppear, which means every time you come to viewController A, this query will be executed irrespective of you have removed the observer or not.
Try putting the same query in viewDidLoad which means, the query will be called once and don't remove the observer anywhere. Now the query would be called only when data gets changed in firebase.
I'm doing my meteor app and it has 1 Collection: Students
In Server I made a Publish that receives 3 params: query, limit and skip; to avoid client to subscribe all data and just show the top 10.
I have also 3 Paths:
student/list -> Bring top 10, based on search input and pagination (using find);
student/:id -> Show the student (using findOne)
student/:id/edit -> Edit the student (using findOne)
Each Template subscribe to the Students collection, but every time the user change between this paths, my Template re-render and re-subscribe.
Should I make just one subscribe, and make the find based on this "global" subscription?
I see a lot of people talking about Template level subscription, but I don't know if it is the better choice.
And about making query on server to publish and not send all data, I saw people talking too, to avoid data traffic...
In this case, when I have just 1 Collection, is better making an "global" subscription?
You're following a normal pattern although it's a bit hard to tell without the code. If there many students then you don't really want to publish them all, only what is really necessary for the current route. What you should do is figure out why your pub-sub is slow. Is it the find() on the server? Do you have very large student objects? (In which case you will probably want to limit what fields are returned). Is the search you're running hitting mongo indexes?
Your publication for a list view can have different fields than for a individual document view, for example:
Meteor.publish('studentList',function(){
let fields = { field1: 1, field2: 1 }; // only include two fields
return Students.find({},fields);
});
Meteor.publish('oneStudent',function(_id){
return Students.find(_id); // here all fields will be included
});
I'm creating a customization where on a click of a button, I need to allocate a charge for a particular purchase order / invoice journal.
From the front end, I would accomplish this by following the purchase order life-cycle and invoicing it. I would then go under the invoice tab of the PO, click Invoice Journals -> Charges -> Adjustment . This will open up my desired form where I will select a charges code, charges value, currency and category, and then I will click 'Ok' and have the system take care of the rest of the process.
Form name: MarkupAllocation_VendInvoiceTrans
Parent form Name: VendInvoiceJournal
You can see that the child form gets called with a few parameters such as the invoice number, there obviously needs to be that link. If I go into the AOT under forms, I right click and open up VendInvoiceJournal, but I wouldn't be able to open up MarkupAllocation_VendInvoiceTrans because it requires parameters.
Objective:
A: To open MarkupAllocation_VendInvoiceTrans through code where I manually pass those parameters to link to the parent table. I would provide the invoice number and such. The objective is to skip opening the parent table and manually going into the adjustments. I want to open that form directly and have it link to whichever record I specify.
B: I need to be able to pass a _ChargesValue parameter and have that be pre-populated for me. I don't know if this is possible, so I wanted to ask and confer. Ideally, I should be able to click a button on my custom form, and have MarkupAllocation_VendInvoiceTrans form directly open for a specified invoice, with pre-populated values on the line.
I know I should be tackling this problem one step at a time, so step A is priority number one.
I can open up the parent form with relative ease like so, but I cannot do the same for the child form. Obviously the same time of approach won't work, as I need to specify the relationship of the parent table before I open it.
private void allocateMarkup()
{
Object formRun;
Args args = new Args();
VendInvoiceJour jourTable;
;
select * from jourTable where jourTable.PurchId == 'PO000001191';
args.name(formstr(VendInvoiceJournal));
args.record(jourTable);
formRun = ClassFactory.formRunClass(args);
formRun.init();
formRun.run();
formRun.wait();
}
How would I be able to do so?
(Side note, I realize this whole form calling could be avoided if do all the transactions programmatically instead of letting the out of the box functionality handle it, but the markup and allocation logic is a beast of it's own and to me seems much more complicated than doing this. If someone has done it this manual way, any help on that would be greatly appreciated as well)
If I read your post right, you just want to open the Charges>Adjustment for a certain invoice. Here is one simple method:
MarkupAdjustment markupAdjustment = new MarkupAdjustment();
markupAdjustment.vendInvoiceJour(VendInvoiceJour::findFromPurchId('PO 120079'));
markupAdjustment.run();
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")