I have a CollaborativeString. I'd like to display each Collaborator's cursor position as they are editing it. I can model a cursor using an IndexReference into the string. And I can allow each Collaborator to maintain their own cursor model inside a CollaborativeMap from Collaborator IDs to cursors.
But, what happens when a Collaborator leaves? Since there's no server component, I guess the other users have to handle cleaning dead items out of the map? And what if everyone has left, and there's nobody to clean up the last one? I guess it'd have to be cleaned up by whoever joins next.
I suppose it's not so bad to have all users listening on CollaboratorLeftEvent and racing to delete the corresponding item, since deleting the same item twice shouldn't be much of a problem. Is it a problem? And then I can make another check over the list if you join and you are the first Collaborator, or every time a Collaborator joins so I don't have to worry about faulty clients messing it up.
Am I overlooking a better way of doing this?
I think you basically have the right idea. You should listen for collaborator leave/join events and update what is being tracked appropriately. As you say, its OK for multiple people to make the changes for leave, as they will do the same thing.
The Realtime Playground has an example of this.
Related
I have been developing some things and you know during early prototyping types and tables change quickly... it would be nice to cleanup the old data and start again in certain meshes.
For now I was using the example HTTP server so I deleted data.json; but I forgot the localStorage in the browser also needs to be cleared.
One might suppose you could put(null)
I asked on gitter and got
https://github.com/amark/gun/wiki/delete
except for deletes , lol, our excuse is "It works like your OS, when you delete >something it just gets tossed in the trash/recycle bin. That's all."
better safe than sorry though
if you are trying to "delete" stuff because you messed up while developing >something, follow this three step process: 1) localStorage.clear() in every >browser tab you have up, 2) Crash the server and rm data.json, 3) restart >everything. You should then have a clean slate. Often times while I'm >devleoping something I put localStorage.clear() at the top of my code so I only >have to worry about clearing the server.
Welcome to the gun community! Thanks for asking questions.
Yes, deleting data is most simply done with gun.put(null). Take:
var gun = Gun();
var users = gun.get('users');
users.put({alice: {name: 'alice'}, bob: {name: 'bob'}});
// now let's delete bob
users.path('bob').put(null);
If (as you mentioned in the question) however, you mean "delete data" as in wanting to clear out mistakes while developing your app. You'll want to do what you mentioned: localStorage.clear() in all browsers, crash the all servers and rm data.json.
For other developers, it might be useful to know that gun uses a type of tombstone method. You can't actually delete nodes themselves, they just get de-referenced, kinda like how your OS just moves files into a trash/recycle-bin. This tombstone method is very important in a distributed environment, such that the "delete" operation is replicated to every peer.
Thanks for answering your own question though! As always, if you get lost or need help hop on the https://gitter.im/amark/gun .
We have multiple projects with multiple portlets and need to send an array of objects between them.
Our situation:
One of the porlets is like a "Master-portlet", it will be responsible for all the REST-calls and consume json-data and parse it to Java-Objects.
All the other portlets will receive an array of objects and show them to the user.
Our thoughts and solution:
We wanted to implement this by sending arrays of objects trough events. One of the "smaller" portlets will send an event to the "Master-portlet" and the "Master-portlet" will then answer with a new event and send the right array of objects back.
Our problem:
We dont know how to send arrays of objects trough events. Is this even possible?
Also we are not sure if this is the right way to solve this. Are events ment to send a bigger amount of data?
Is there a better solution for our case? Maybe it would be better to implement a database and all the portlets get the information from there?
Consider portlet events (and portlets) the UI layer of your application. Based on this, judge if the amount of data that you send back and forth makes sense or not. Also, if you closely couple the portlets, you're just hiding the fact that they can only function together - at least a questionable idea. You rather want them to react to common circumstances (events), but not rely on a specific source of events (master portlet) being available.
That being said: The more complex the data is that you send as payload of a JSR-286 event, the easier you run into classloading problems in cases where your portlets are in different webapplications. If you restrict yourself to Java native types (e.g. String, Map, etc) you will omit problems with the classloader.
Typically you want to communicate changes to the current context (e.g. new "current customer" selected - and an identifier) but not all of the particular data (e.g. the new customer's name and order history). The rest of the data typically comes through the business layer anyway.
That's not to say that you absolutely must not couple your portlets - just that my preference is to rather have them very loosely coupled, so that I can add individual small portlets that replace those that I thought of yesterday.
If you have some time, I've covered a bit of this in a webinar last year, I hope that this adds some clarification where I was too vague in this quick answer.
Many examples on the net show you how to use ng-repeat with in-memory data, but in my case I have long table with infinite scroll that gets data by sending requests to a REST API (scroll down - fetch some data, scroll down again - fetch some more data, etc.). It does work, but I'm wondering how can I integrate that with filters?
Right now I have to call a specific method of API service that makes a request based on text in "search" input box and then controller updates $scope.data.
Is it possible to build a custom filter that would do that? And then my view would be utterly decoupled from the service and I could declaratively tell it how to group and order and filter data, regardless if it's in-memory or comes from a remote server, server that can serve only limited records at a time.
Also later I'm gonna need grouping and ordering as well, I'm so tempted to download the entire dataset and lock parts of the app responsible for grouping, searching and ordering (until all data is on the client), but:
a) that dataset is huge (hundred thousands of records)
b) nobody wants to deal with cache invalidation headaches
c) doing so feels so damn wrong, you don't really expect me to 'keep' all that data in-memory, right?
Can you guys point me to maybe some open-source examples where I can steal some ideas from?
Basically I need to build a service and filters that let me to work with my "pageable" data that comes from api, like it's in memory-data.
Regardless of how you choose to solve it (there are many ways to infinite-scroll with angular, here is one: http://binarymuse.github.io/ngInfiniteScroll/), at its latest current beta version, ng-repeat works really bad with large amount of data - so do filters. The reason is obvious - pulling so much information for changes is a tuff job. Moreover, ng-repeat by default will re-draw your complete list every time something changes.
There are many solutions you can explore in this area, here are the ones I found productive:
http://kamilkp.github.io/angular-vs-repeat/#?tab=8
http://www.williambrownstreet.net/blog/2013/07/angularjs-my-solution-to-the-ng-repeat-performance-problem/
https://github.com/allaud/quick-ng-repeat
You should also consider the following, which really helps with large amounts of data.
https://github.com/Pasvaz/bindonce
Updated
I guess you can't really control your server output, because filtering and ordering large amount of data are better off done on the server side.
I was pointing out the links above since even if you write your own filters (and order-bys), which is quite simple to do - http://jsfiddle.net/gdefpfqL/ - (filter by some company name and then click the "Add More" button - to add more items). ordering by is virtually impossible if you can't control the data coming for the server - the only option is getting it all, ordering and then lazy load from the client's memory. So if each of your list items doesn't have many binding by it self (as in the example I've added) - the list item is a fairly simple one (for instance: you simply present the results as a plain text in a <li>{{item.name}}</li> then angular ng-repeat might work for you. In this case, filters will work as expected - say you filter by searched text:
<li ng-repeat="item in items | filter:searchedText"></li>
even for new items added after the user has searched a text, it will still works because the magic of binding.
I have a WPF application that uses entity framework. I am going to be implementing a repository pattern to make interactions with EF simple and more testable. Multiple clients can use this application and connect to the same database and do CRUD operations. I am trying to think of a way to synchronize clients repositories when one makes a change to the database. Could anyone give me some direction on how one would solve this type of issue, and some possible patterns that would be beneficial for this type of problem?
I would be very open to any information/books on how to keep clients synchronized, and even be alerted of things other clients are doing(The only thing I could think of was having a server process running that passes messages around). Thank you
The easiest way by far to keep every client UI up to date is just to simply refresh the data every so often. If it's really that important, you can set a DispatcherTimer to tick every minute when you can get the latest data that is being displayed.
Clearly, I'm not suggesting that you refresh an item that is being edited, but if you get the fresh data, you can certainly compare collections with what's being displayed currently. Rather than just replacing the old collection items with the new, you can be more user friendly and just add the new ones, remove the deleted ones and update the newer ones.
You could even detect whether an item being currently edited has been saved by another user since the current user opened it and alert them to the fact. So rather than concentrating on some system to track all data changes, you should put your effort into being able to detect changes between two sets of data and then seamlessly integrating it into the current UI state.
UPDATE >>>
There is absolutely no benefit from holding a complete set of data in your application (or repository). In fact, you may well find that it adds detrimental effects, due to the extra RAM requirements. If you are polling data every few minutes, then it will always be up to date anyway.
So rather than asking for all of the data all of the time, just ask for what the user wants to see (dependant on which view they are currently in) and update it every now and then. I do this by simply fetching the same data that the view requires when it is first opened. I wrote some methods that compare every property of every item with their older counterparts in the UI and switch old for new.
Think of the Equals method... You could do something like this:
public override bool Equals(Release otherRelease)
{
return base.Equals(otherRelease) && Title == otherRelease.Title &&
Artist.Equals(otherRelease.Artist) && Artists.Equals(otherRelease.Artists);
}
(Don't actually use the Equals method though, or you'll run into problems later). And then something like this:
if (!oldRelease.Equals(newRelease)) oldRelease.UpdatePropertyValues(newRelease);
And/Or this:
if (!oldReleases.Contains(newRelease) oldReleases.Add(newRelease);
I'm guessing that you get the picture now.
I have a situation where, in a model's afterSave callback, I'm trying to access data from a distant association (it's a legacy data model with a very wonky association linkage). What I'm finding is that within the callback I can execute a find call on the model, but if I exit right then, the record is never inserted into the database. The lack of a record means that I can't execute a find on the related model using data that was just inserted into the current.
I haven't found any mention of when data is actually committed with respect to when the afterSave callback is engaged. I'm working with legacy code, but I see no indication that we're specifically engaging transactions, so I'm trying to figure out what my options might be.
Thanks.
UPDATE
The gist of the scenario is this: We're taking event registrations, but folks can be wait listed. A user can register (or be registered) for a given Date. After a registration is complete, I need to check the wait list for the existence of a record for the registering user (WaitList.user_id) on the date being registered for (WaitList.date_id). If such a record exists, it can be deleted because it's become an active registration.
The legacy schema puts me in a place where the registration isn't directly tied to a date so I can't get the Date.id easily. Instead, Registration->Registrant->Ticket->Date. Unintuitive, I know, but it is what it is for now. Even better (sarcasm included), we have a view named attendees that rolls all of this info up and from which I would be able to use the newly created Registration->id to return Attendee.date_id. Since the record doesn't exist, it's not available in the view.
Hopefully that provides a little more context.
What's the purpose of the find query inside of your afterSave?
Update
Is it at all possible to properly associate the records? Or are we talking about way too much refactoring for it to be worth it? You could move the check to the controller if it's not possible to modify the associations between the records.
Something like (in psuedo code)
if (save->isSuccessful) {
if (onWaitList) {
// delete record
}
}
It's not best practice, but it will get you around your issue.