My app is based on notifications from the server, using SignalR I am getting the entities and adding them using
manager.createEntity(entityType, entity, breeze.EntityState.Unchanged);
The UI is based on Angular grid which is bind to all the entities of certain type, how ever when I am adding new entity the grid isn't being updated, my assumption was that I am bind to the cache and not other collection. Same issue when I am removing entity
As #PWKad pointed out in the comments above, the getEntities function builds an array each time it is called, returning the entities from its cache that match the parameters. The resulting array won't be updated when the cache changes.
In your case, you should store the array that's returned by getEntities, then add each new entity to it after that:
scope.gridList = manager.getEntities(entityType);
// ... then later:
scope.gridList.push(manager.createEntity(entityType, entity, breeze.EntityState.Unchanged));
Related
This one is making me crasy : I have an EF model built upon a database that contains a table named Category with 6 rows in it.
I want to display this in a drop down list in WPF, so I need to bind it to the Categories.Local Observable collection.
The problem is that this observable collection never receives the content of the database table. My understanding is that the collection should get in sync with the database when performing a query or saving data with SaveChanges() So I ran the followin 2 tests :
Categories = _db.Categories.Local;
// test 1
Debug.WriteLine(_db.Categories.Count());
Debug.WriteLine(_db.Categories.Local.Count());
// test 2
_categories.Add(new Category() { CategoryName = "test" });
_db.SaveChanges();
Debug.WriteLine(_db.Categories.Count());
Debug.WriteLine(_db.Categories.Local.Count());
Debug.WriteLine(_categories.Count());
The test 1 shows 6 rows in the database, and 0 in local.
The test 2 shows 7 rows in the database, and 1 in local (both versions)
I also atempted to use _db.Category.Load() but as expected, it doesn't work because it is db first, not code first.
I also went through this page https://msdn.microsoft.com/en-us/library/jj574514(v=vs.113).aspx, created an object-based data source and linked my combo box to it, without success.
Does anyone know what I am doing wrong?
Thank you in advance for your help.
The DbSet<T> class is IQueryable<T>, hence DbSet<T>.Count() method maps to Queryable.Count<T> extension method, which in turn is translated to SQL query and returns the count of the records in the database table without loading anything into db context local cache.
While DbSet<T>.Local simply gives you access to the local cache. It contains the entities that you added as well as the ones being loaded by query that returns T instances (or other entities referencing T via navigation property). In order to fully load (populate) the local cache, you need to call Load:
_db.Categories.Load();
The Load is a custom extension method defined in QueryableExtensions class, so you need to include
using System.Data.Entity;
in order to get access to it (as well as to typed Include, XyzAsync and many other EF extension methods). The Load method is equivalent of ToList but without overhead of creating additional list.
Once you do that, the binding will work. Please note that the Local will not reflect changes made to the database through different DbContext instances or different applications/users.
Here is my problem, I hope some one can help me here, I'm developing a mobile app in qx.
In the application.js I call for a JSON in a server through the qx.store.json(url) that creates a model that I bind to a offline model to access the data offline in the app.
Everything good so far then when I try to access the data in the offline model it doesn't let me. The original JSON data is
array(timestamp=>time(),
userdata=>array(
array(userid=>0...),
array(userid=>1...)))
When I debug the JSON or the offline data with obj.getItem(1) it always returns me qx.data.model.userdata.
I'm trying to use the data inside the array of userdata to validate a user in a foreach statement but qx.data.model.userdata always returns undefined.
I try obj.getUserdata(), obj.getItem(1), obj being the offline model.
What am I doing wrong? It isn't a model a store for data, or it can only be used as binding data to an widget?
If the item at index 1 was an Array, obj.getItem(1) would return an instance of qx.data.Array. Since it returns an instance of qx.data.model.userdata, that means the model item is actually an object with a single property named "userdata" and you would access the value by calling obj.getItem(1).getUserdata().
I'm just getting my head around BackboneJS, but one of the (many) things I'm still struggling with is how exactly the Models Sync up and relate to the serverside DB records.
For example, I have a Model "Dvd", now I change an attribute on the "Dvd" Model, the Name for example, and then I call save(), how exactly does the server side know what DB record to update? Does Backbone hold the DB row ID or something else?
Yes, typically you will set up your Backbone models so that they have database row IDs for any objects you're working with. When one of them is brand new on the client side and not yet saved to the server, it will either have a default or no ID, which doesn't matter since the server will be assigning the ID if and when the initial save transaction succeeds.
Upon saving or updating a model item, Backbone expects the server to reply with some JSON that includes any attributes that have changed since the save or update request was made. In the response to the initial save request, the server informs the client of a newly saved item's row ID (and you can also send along any other information you might need to pass to the client at the same time).
By default, the 'id' attribute of a model object is assumed to be its unique identifier, but backbone lets you change this if you're using a different identifier for the primary key. Just give your model an idAttribute parameter (see the docs for Backbone.Model.extend()) to do that.
Meanwhile, either the urlRoot parameter or a url function can be given to your models to characterize the urls that should be used to send the various ajax requests to the server for a given model.
Sorry this is a noob question but if I only need some initial data when the application first loads is a collection always needed or can the model fetch the data and pass it directly to the view?
Nothing in backbone is really "required". It's a very thin, more-than-one-way-to-do-it framework. Jeremy recommends data that can be bootstrapped in the initial page load be handled that way, so your HTML could include you initial data as JSON in a <script> tag. You can pass that JSON to a Backbone.Collection (if it's a list of similar records) or a new Backbone.Model (if it's a single domain object). You can also just use a model and call model.fetch to get your initial data. Model vs. Collection is more about single domain object with name/value pairs vs list of many objects where iterating, sorting, filtering are common.
I have a page where it displays a filtered model instance list and allows users to update some fields of it or add new fields as a form.
I am curious what wpuld be a clever way of doing this, to delete and resave all the input data or make comparison for each data and save edited / new fields& entities.
I would like to mind you that I use postgres for saving these values and I display around 20 entries for this form.
The QuerySet object has the update() method - it's used in ie. Admin Panel for bulk updating multiple selected objects from change lists. Here is the method reference at django's official documentation.
How to use it:
Just create queryset with the models you want to update (assumng that MyModel has field named 'my_field'):
qs = MyModel.objects.all()
qs.update(my_field=value)
That's it - remember that update() method will not send any signals like the save() method - it will just run query directly to database.
As for 'adding fields via form' - I don't know if I got it right? You want to add additional related models or dynamically add fields to the model table on database?
If you want to add related models then use InlineFormset (http://docs.djangoproject.com/en/dev/topics/forms/modelforms/#inline-form) - it's quite easy to handle.
Otherwise you have to add fields to models' _meta as described here: How dynamic add custom field to model.