I have a react/flux application with websockets that works fine. All communication happens inside my WebSocketUtils file. Whenever I receive new data from my server as push events I trigger an action and let the whole Flux flow happen. In the end that causes my view to rerender.
The individual views are connected to my store via Higher Order Components. All new data is passed into my view as props. As these are changeable I use these props and set them as my initial state (which is ok).
Now let's say I have user A and user B looking at the same view of my application (on different machines of course).
User A edits some data
User B also edits some data
User A saves this new data
User B receives new data via push event and the view will rerender
Problem: User B lost all the data that was edited but not yet saved.
Any ideas how to solve this problem?
User WiredPrairie is correct in their comment. This isn't a React or Web Sockets problem, it's a problem with conflict resolution.
What would you expect to see in that situation? You would want the two states to be kept temporarily until you can either merge them automatically (unlikely) or present the user with some kind of interface to review their changes.
You could also prompt user B that user A is editing their data, just to keep them informed :)
A granular approach to editing would help - like in a Google Spreadsheet a user will often only edit a cell at a time, so in your situation you may only send field-level information across the wire (as opposed to record-level), and that would help avoid conflicts.
At the end of the day though, this is less about specific technology and more about your application: you need to work out how you'd like it to behave.
Related
I am new to react and developing the react application, where I want that user can save his/her selected values on the frontend and later on can also see those values via clicking a button and user can see what values have been selected previously. now the question is how to provide this functionality, I have studied that either it could be done by local-storage or by the data binding concept in react, but I have no clue which one is best to implement in my scenario.
Let me explain to you with the help of a diagram.
(The first Image with Indicator Generation)This is the main page of my React Application, under the section of "Question & Indicator" there is a thing called Associated Indicator, these are the values which user have select itself on the Frontend side.
(The second image with detailed user-controls) This is the page where all the user-controls are defined, here user can select the values and at the end when user clicked "Associate" it will be associated and the values have been shown under the section of Associated Indicators, from that user when clicking any of the associated indicators it will show all the values selected by user on front end.
Cheers.
Preserving data in a web app is not related to React -or any other front end technology specifically.
Data binding is a concept on how to update your views when certain data changes, and it is not related at all to how data should be saved. But related to how modern front end technologies like react and angular render your components.
You can save data in a web app using different methods, each one is suitable for certain use cases - and so you should use the one that suits you.
For example you can use any of the following:
Cookies: old way of saving data on the front end, can stay infinitely but can also be deleted if the user decided to delete them or clear data from his browser. Cookies Get send to the server-side with each request done with the browser, has limitations with size.
IndexedDB: This one is literally like a database inside the browser, really fast when querying data, also has bigger Size limitations than both Cookies, and LocalStorage. However, this is a really low level API. Won't recommend to use it, unless you really need its features. Can also stay infinitely, and can also be deleted by user.
LocalStorage: New browser API to persist data, much more easier to handle than Cookies And IndexedDB, Can stay infinitely, but can also be deleted by the user. Has bigger size limits than Cookies, but less than IndexedDb.
SessionStorage: Data saved for each tab, and data cleared when page session ends.
Finally If You want data that persist for forever and the user can't delete it, you have to do your own solution in the backend.
I have a form that is four pages. The user clicks next and this leads them to the next page of the form. On the fourth page the form is complete.
What is the best practice?
Do I do a POST after each page, so 4 different times, or should I do one big POST on the last and final page pushing all the user data to the database?
Each page posts to a different endpoint.
My form is created using redux-form and react.
Either works, the main advantages I see are:
Sending one complete form - advantages:
No database pollution
Less network overhead
Sending 4 partial forms - advantages:
You can see where each user stopped - this may be useful data if they
are purchasing a service or signing up for an account. Do a lot of
people fill out the first two sections only to see the third and
navigate away?
You can use this to save the form server-side for people to complete
later. You can also do this with Redux / Local Storage for session /
browser storage, but you may want the functionality of a user
starting a form on one device and completing it on another, requiring
server-side storage of the form.
If you don't plan to implement the functionality of server-side storage, and if you don't need the extra analytic data of where they stop on the form - just go right ahead and send it all at once. I would suggest at a minimum, you try to save the form to Local Storage to make it easy for the user to pick up where they left off.
I want to say it depends on your database model and the data you are fetching from the form. It may be that the data retrieved from the first form is enough to do a desired database modification; in that case, it may be nicer to immediately send the POST data. However, if that data may be needed in a future query, it might be better to send it all at the end to avoid re-sending old data. Some may also argue that doing multiple posts is worse in terms of network usage
Note: most importantly try to avoid sending duplicate data
When polling a model (object) or pushing a model from a RESTful API to AngularJS via xSockets the data in input-fields is overwritten.
Let's say I edit the first name of a user and while I edit the user xSockets or the timed polling using the $interval to refresh the model, is writing over the changes I have made to the first name before I had a chance to save.
How can I push or poll a model into the view without overwriting the input-field as I am editing?
Your information is a bit limited, but assuming that I understand the question correctly, you have two options.
You can disable realtime data refreshing on the edit page (I wouldn't let my app continuously refresh data where I am supposed to be providing input anyway).
You could add a change listener on your inputs that tells xSockets to not refresh the data on that field again until you have submitted the form.
Again, I'm not entirely sure what your situation is without seeing any code, but hopefully this helps.
Well, as technology progresses, issues we solved long ago crop up again.
Back in the dark ages, when PHP and ASP were considered awesome, we always had a problem with view states. If you had a page with say a dozen select combo boxes on it, your user chooses some combination and hits next, then realizes they screwed up and hit the back button on the browser, the combo boxes would be back in the default state, usually with option[0] selected. In order to prevent this, we had to write boatloads of boilerplate code that would save the state of those combo boxes to a cookie, or session variable, or something so that when the user hits the back button, we can reload the combo boxes back to the state they were in when they left.
This problem was compounded even further if you had a datagrid on the screen. Because then you would have to come up with some slick way of saving that grid somewhere to prevent from having to hit the database again.
Then came the light. Browser developers realized that most web developers were on the verge of going back to writing terminal programs in Cobol due to this issue and added UI caching to the browsers. This allowed us webdevs to not have to worry about this anymore except in odd situations.
So, life was good. Then someone came up with the bright idea of trying to replicate GWT without all the hassle and the web explodes with all these javascript frameworks. The one im dealing with specifically at the moment is AngularJS 1.2.10 with Angular-UI. I have until Friday (most likely wednesday tho) to make an initial assessment on if this technology is a viable alternative to our current standard (thats pretty much universally hated) JSF.
So, i follow some guides, pound my head against the desk a few times, and I have an angular app with 3 actual HTML pages, each HTML page with 2 views.
Before you go there, understand we can't use it unless we can do multi-page JS apps. Some of the applications that this will be worked into have been in development for a decade or more and its simply not financially practical to scrap an the entire UI and start over again. We would instead be doing things like taking these 50 struts pages and converting them to angular/rest and linking them seamlessly back into the remaining 800 struts pages of the application.
So in my exercise of playing with this, I encounter my old nemesis. Back button view state issues.
I have been playing with the UI-route system. The fact that I can deep link using the route system solves part of my problems. But, if say I have a search page like this:
view-search
combo: search type [member,nonmember]
combo: result type [detail,summary]
combo: search state {all the states]
textbox: contract number
etc etc etc
And various combinations of combo box selections and text entries comes up with a list of 1000 people. Now the user selects one of those people on the data grid and it takes you to view-detail. Well the fact that you can use routing to do something like index.html#detail/bob is cool, but if the user realizes thats the wrong bob and hits the back button, they get a blank search screen again and they have to enter everything over and worse yet, send another search to the database to rebuild the datagrid. Some of these screens have 50 or more options to choose from when searching for data so trying to put all of them into the URL routing sounds completely impractical to me.
Now in my research I found this post:
Preserve state with Angular UI-Router
And that has promise mainly because I have a view state object that I can store into a Redis database or a session EJB for cases when the user actually jumps out of angular and into the legacy Struts application, then back buttons back into the angular application, but the fact still remains that on some of these pages, that is a huge amount of boilerplate code that we would have to write in order to make it work.
I don't really mind the idea of having to manually save off the view state object and read it back in from a Redis server or something anytime a user enters or leaves an HTML page in the system. What i'm really looking for is a way to automatically generate the object that is to be saved without having to write volumes of boiler code.
Is this possible? I keep reading the ui-route documentation but it doesn't look like this is addressed, at least not that i've translated yet.
If this is possible, what controls should I be looking at?
thanks
-------------- Edit
I just thought of something. There is one central scope to each of the single page applications. (Im basically going to be building a multiple single page apps and hooking them together) So if i use a naming convention, something like this
$scope.viewstate.view-search.searchType
$scope.viewstate.view-search.resultType
$scope.viewstate.view-search.searchState
Then the viewstate object should simply be a js array and when I create a function to move to struts.do, i can simply save that array off to the Redis server as a nested map object. Then when my user back buttons back into the angular app, i can capture that using the route system and retrieve that viewstate object from Redis and insert it back into my scope, thereby rebuilding the scope for the entire single page app in one shot.
Would that work?
I believe that you have a very complicated issue of trying to keep the view states between your varying pages with the amount of data in your pages. I think that the only real effective way to do this is to write an angular service that you can then pass to your various pages. as You already know the service is a singleton that you can use in various controllers and could be utilized to maintain the view state as you described. here take a look that this link and see if it will help: http://txt.fliglio.com/2013/05/angularjs-state-management-with-ui-router/
After some thought what you suggest in your edit might work, but I would still use a service to retrieve that array of data, as it would make it easier to reinsert in to angular scope
I am exploring something similar for an Angular app that I am writing. Keeping a user login during a page refresh is easy. Displaying the state on the page after a refresh is an entirely different problem.
How long must the state be persisted? I'm evaluating two possibilities.
First, saving the state (current form values or whatever) to the database. As the page changes, incrementally save the state to the database. On a browser refresh check the database for saved values.
Second is to use local browser storage. This is 5 megs of storage. 5 megs is a lot of text. Again this data would incrementally be saved into storage. When the browser refreshed, simply load data from localStorage.
I have a nontrivial Angular SPA that uses ui-router to manage multiple views, many of which are visible at the same time. I need models to be visible across controllers, so I have services written that allow me to have controllers pull down fresh copies of model data that has been updated.
I apologize in advance for the length of the question, but I will state the problem then state what I have done to address issues I'm sure others in the Angular community have struggled with.
I believe my problem is not understanding the lifecycle of controllers / views, because I get behavior where a controller initializes correctly the first time I go there, but then seems to never run again, even when I navigate to it using something like $state.go("state name").
In one view (contrived example), I show a summary of information about a customer, and in another view I allow a user to update that customer's more detailed profile. I want a user to edit, say, the customer last name in the detailed view, and have the summary view automatically recognize the change and display it.
I have a fiddle that shows 3 views and a simple password changing Service. The flow goes like this:
You can see each view gets initialized and displays the initial password retrieved from the service. All views are in sync with the DataService.
The middle view allows you to enter a new password and change the one stored in the service. Console logging confirms that the service picks up the new password just like you would expect.
(odd behavior #1) When the DataService receives the new password, I would expect the other 2 views (top and bottom) to display the new one. They don't... they still display the initial password.
There is a button to allow a user to go to another state via $state.go("state name") (a child state of the original) which also retrieves the password and displays it. This works the first time (see #5). Now the top view shows the outdated password, the middle view shows the new one, and the bottom one shows the new one as well. This seems normal, since the new view is invoked after the DataService contains a new password value.
(odd behavior #2) If I click back in the middle view and change the password again, and click the button to change states again, the bottom view (which updated just fine in step #4) no longer updates its copy of the password. Now all 3 views show different passwords, even though I am using a single service to pass values between controllers as suggested pretty much everywhere you look for Angular best practices.
Some possible solutions:
Tim Kindberg has an excellent slideshow here that seems to recommend using ui-router's state heirarchy to "pass" data among views that need to pick up values from other views. For a smaller-scale app I think I would settle on this, but I expect our application to have 30+ views displaying data from over 100 REST endpoints. I don't feel comfortable maintaining an application where all the data is being shared by a complex inheiritance tree. Especially using a routing framework that is at version 0.2.8.
I can use events to have controllers listen for changes in the data model. This actually works well. To accommodate performance concerns, I am using $rootScope.emit() and a $scope.$onRootScope('event name') decorator I found on here. With this approach I am less concerned about event performance than I am about wiring this huge app with a bunch of event listeners tying everything together. There is a question about the wisdom of wiring a large app using angular events here.
Using $watch on the value in the DataService? I have not tried this but I am hesitant to hinge an app this size on hundreds of $watches for performances reasons.
A third-party library like bacon.js (or any of a dozen others) that may simplify the event spaghetti, or create observable models that my controllers can watch without the risk of $digestageddon. Of course, if there is a concise way to handle my issue using Angular, I'd prefer not to muddy the app with 3rd party dependencies.
Something that lets controllers actually reference .service modules by reference, so I don't have to depend on tons of event wiring, complex state hierarchies, 3rd party libraries, or seeding the app with hundreds of $watches and then kicking off $digests to update controllers' references to Angular services?
Some solution that relies on time-tested OO and design patterns and not a 3rd-party library or framework that has a version that starts with 0.*.
Thanks in advance... I appreciate the help!
This is no problem of ui.router. If you intend for your model (your data service) to be a single source of truth, you have to refrain from destroying it.. err.. the reference to it that is. And in your case, assigning a primitve (a string) directly to the scope, instead of a reference to it. In other words...
var password = {pw:'initial value'};
and then later setting/binding only on
password.pw = newpassword
{{password.pw}}
Heres a fiddle. And also here is a short little read on scopes, It also includes a video of an angular meetup where Misko talks about "always have(ing) a dot in your model" link and how the $scope is a place to expose your model, not be your model. (aka not a place to assign primitives like password = 'initial value')
Hope this helps!
try remove the animation property of your ion nav view.
remove the property
animation="slide-left-right"
it would be ok.