I am still relatively new to development for Windows Store Apps in XAML/C# and I'm currently dealing with a very random and intermittent problem with an app I have written.
Firstly a quick overview of how my app works - user logs on once a day, downloads data from web service and stores the data in xml files. Each time the app opens/resumes the data is loaded from xml, deserialized and stored in memory in the Application.Resouces Resource Dictionary.
The objects I am storing are my own classes which contain Observable Collections of other classes. I have declared these in App.xaml
<localdata:MyClass x:Key="MyClassResource">
When a page needs this data I reference it using
MyClass myClass = (MyClass)App.Current.Resources["MyClassResource"];
and bind it to controls. The user updates the data and these changes would also be saved to file periodically.
I am now starting to doubt whether this is the correct approach for storing my data.
Every so often the users reports problems with the stored data - I don't have enough details to fully discuss the specific problem right now but I wanted advise on whether it is fine to store my own objects in the Application Resource Dictionary.
There's nothing wrong with your approach. It is actually a very common way to create and access the viewmodel. There is an excellent blog post by Paul Stovell describing different approaches to create and access the viewmodel.
Create viewmodel from code-behind within the view
Inject the viewmodel as dependency into the view
Assign viewmodel to view's DataContext property
Set viewmodel via XAML to DataContext property
Define viewmodel as resource in XAML
Use a view model locator in XAML
DataTemplate property in XAML
DataTemplate and view class in XAML
The referenced article describes all 8 approaches with examples. Your approach is number 5.
Related
According to apple doc's Persistent Store Types and Behaviors, the built-in persistent store types of core data are
1. XML
2. Binary
3. SQLite
4. In Memory
My Question is,
Among these which is the default store type when we use core data model in xcode and how can we change it
Well, NSPersistentStore is an abstract base class. One of its four subclasses must be deliberately created in code. So, there is not really a default store type.
There is, however some template code which gets generated when you choose one of the New Project or New Target templates in Xcode. In the current version (Xcode 10), when you switch on the Use Core Data checkbox, you get in the AppDelegate implementation a lazy var persistentContainer property which provides a singleton NSPersistentContainer object. This is by default the store you will use in the new target. But what store type is that? Well, the persistent store(s) of a NSPersistentContainer are specified in its persistentStoreDescriptions array property. By default, this array contains one persistent store of type SQLite, backed by a file in the Application Support folder of your app's container. This is, in a round-about way, the default store type you asked about.
The procedure to change this store type is explained in the Discussion section of the documentation of NSPersistentContainer.persistentstoredescriptions.
So you see the default is actually in the Xcode Project Templates. To get what you want, you can place the code you wrote after reading that documentation into a new Project Template and add it to your ~/Library. You can either override one of the default Project Templates, or create your own with a new name. A basic example is given in this blog post by Jake Craige. If that is not enough for you, Keith Harrison has published a quite thorough reverse engineering of Xcode Project Templates.
To not have to keep repeating some validations, for example, who can see a button in a certain status of a document in the worlflow, I'm using session, scope, and session variables to store the user roles and application variable to store the Status related to each area.
I was evaluating whether it would be better from a performance and build point of view to implement a managed bean, to return the user roles and the possible statuses of each participating workflow area. Would it be the best structure in fact? What do you think? I do not have much experience in java. How could I construct the structure in java, several methods, one for roles and the other for set of status associated with the area that would name the related method? You could return the results of this method in arrays, or there is a better return structure.
Thanks a lot!
My best suggestion is to adopt the pageController Methodology. Then it's more like true MVC. This has been talked about on NotesIn9 screencast many times but basically you have a java object that's bound to your XPage. In effect it's a viewScoped bean that holds all your page logic. Then you can have methods like isGroupMember(), hasRole() etc and calculate that on the pageInit. There's little need to hold onto that in sessionScope in my opinion. So for example I have this in my pageController :
public boolean isGroupMember(String groupName) {
return JSFUtil.getXSPContext().getUser().getGroups().contains(groupName);
}
So that's available to each page. BUT I don't need to copy that snippet onto every page controller. In Java you can have your page controllers extend a more generic class. so I have a "base.pageController" class. All the specific page controllers extend that. So this isGroupMember() code goes into the base and then it's available to be used on every XPage. Doing it this way gives you the ability to have generic functions like this and then hold more specific function that are only for the individual page.
You can also have a hasRole() function etc...
Recommend you check out this video : http://www.notesin9.com/2016/08/25/notesin9-196-no-dependency-page-controllers/
Also for a question like this, I recommend you just use the xpages tag. Adding others like javabeans can bring people in who know nothing about XPages and XPages is unique enough of a beast that outsiders can cause some confusion on occasion.
I am coding an MVC internet application, and I have a question in regards to using the ViewBag.
In many of my controllers, I have SelectList objects, where the user can select an object. The object that is selected is a foreign key value for my model.
My question is this: Should I use ViewBag for this? How secure is the ViewBag? Should I use values in my ViewModel instead of the ViewBag?
Thanks in advance.
Use your view model.
When the ViewBag was implemented (MVC 3) dynamic typing was new (.NET 4.0) and it was put in just as a side-option to ViewData or to quickly generate a view without the need for additional classes.
Any serious MVC project will take advantage of a model/viewmodel with a strongly typed view.
There are no security concerns with either because both essentially only exist through the controllers lifespan.
There are no security concerns with ViewBag since it is disposed once rendered in the View.
I think the answer really should be "it depends". For example, if you have 6 collections required to populate dropdown lists aand you want to get the data posted back, you should definitely use a ViewModel for this. Since 6 collections will be hard to manage if they are stuffed in ViewBag with no strong typing in the view, especially if another developer comes along later needing to do maintenance to the view.
Generically everything should be done inside a view model. That's what a view model is. A class that you specifically define to meet the requirements of your view. Here is an image depecting when to Use TempData, ViewBag or ViewData
I've written a new back-end Java component (extending UIComponentBase) as an alternative for the ExtLib Application Layout control. The control needs to show a collection of data that is looked up from another Notes application. The data is user dependant and doesn't change from page to page so, to avoid repeatedly doing a lookup to the other application, I want to store it in the session scope. (Note that because this is a layout control, there will only ever be one per page.)
I know I could use a session-scoped maanged bean (and have done in previous iterations) but the data only needs to be used in this control and shouldn't be used elsewhere on the page which it could be with a bean. So my question is, what's the best practice approach I should take here? Should I just directly store the data in the sessionMap or am I missing a trick with the component stateHolder? Or am I stuck with using a bean?
Thanks
(Edited for clarification)
It looks like you're talking about your own back-end Java components rather than Custom Controls within a single NSF.
I'm not sure at what level, when you write your own native XPages components, the properties are cached by the stateHolder when calling saveState(). I would presume no higher than View, for the reasons Frantisek says, that otherwise it would be unclear which instance to update if you had multiple on one XPage but one on another. It couldn't update both at the same time on the same page, so I would guess that each is a separate instance. As a result, the same component on multiple pages would be a separate discreet instance.
But there's nothing stopping you, in specific setters of the component, writing to sessionScope as well as the private property, and then doing the reverse on the getter. I'm not sure if you'd want to try the internal property before trying sessionScope or vice versa. It would depend how you wanted to handle the situation of the same sessionScope being updated from multiple pages (if the collection could change).
Has anyone been able to use a SubSonic generated collection as a "business object datasource" with Microsoft report (rdlc)? I have generated the SubSonic class code but for some reason the report datasource window is not seeing the class as a potential object collection datasource.
Is there something I need to do for this to work?
Thanks in advance...vsdotnetguy
I have loaded Reporting Service reports from business objects before (loaded via NHibernate -- which isn't exact but close enough for argument sake).
Couple of key points:
1. return your objects in List, even if you are only returning one object.
2. You want FLAT business objects. You might have to go thru a DTO transformation to get that. By flat, I mean the most complex property you can have in a business object is a string and a number (int, decimal, double). If you are expecting to grab a value like this:
myObject.Customer.Name, forget it. Create a CustomerName property.
3. If you need data from multiple places try to break up your reports into subreports. You key off of the datasource key to figure out what data to return to the report.
I'll add more as I remember, it has been a few months since I've done this.
Yes I've done it, you should only need to make sure the project containing your reports references your SubSonic project (obviously :).
Sometimes I've also found that Visual Studio can get a little borked and require a restart before repopulating the datasource window with SubSonic generated objects.
Thx Chris and Adam,
Here is the answer I found.
In my case I wanted to dynamically set the main and subreport datasources at run time using the SubSonic object collections. However, I also wanted to design the report layout using drag and drop of the datasource columns.
But I was unable to design the report using drag&drop because none of my SubSonic collections were showing up in the Website Data Sources.
However, later while I was doing some control binding using the ObjectDataSource control, I noticed that NOW my SubSonic collections were showing up in the Website DataSources window and I could drag and drop the report layout.
So if you are dynamically setting the report datasources at run time and ARE NOT using the ObjectDataSource control already in your project, you MUST add a dummy ObjectDataSource control to one of your aspx pages. This will then make the business object datasources show up in the report designer.