its said that 1 ViewModel has 1 View.
1 View is for me a UserControl. What if my UserControl has different areas filled with data from different entities, do I have then several Views and need to build several ViewModels?
e.g: I display in a UserControl 3 entities: customer(listbox),order(datagrid),product(datagrid). Each of those "data areas" has add+remove buttons and textboxes to enter data.
Actually each of those "data areas" are put in its own GRID having so the posibility to set a individual datacontext.
1.) Should I now create 3 ViewModels CustomerVM,OrderVM and ProductVM?
2.) Are those 3 "data areas" seen as an own sort of separated View, although I have not put them in 3 UserControls.xaml files ???
3.) When this one UserControl is inside a TabControl`s tabpage where do I load the 3 entities related data? Inside the MainViewModel? I want to show/load that data only when the user clicks the tabheader.
No, you can do all that in the one viewmodel. The job of the viewmodel is to hold the data for the view, and if necessary transform that data so the view can consume it. There is nothing that says a viewmodel has to hold specific types of information, i.e. there are no rules that state "it may only hold customer info and not order info".
Having said that, there is also no reason why the viewmodel cannot be consumed by several different views (give them all different instances, of course) - this would show that you have a good separation of concerns between your views and viewmodel. Personally, i code my viewmodels so that they have no idea that the view exists. There is also no reason why the view has to consume everything that the viewmodel exposes, although binding a CustomerView to a CustomerOrderProductViewModel is going a little too far.
Edit: let me explain that last paragraph a little more.
Example 1: i have a new V which shows customer information, and i have an existing VM which has customer info AND order info
I would be reluctant to use this VM for this V, because while it does have the client info i need, it has too much info - i'm using the VM out of the context is was originally intended for.
Example 2: i have a VM that contains full client info, like their postal and residential address, their phone numbers, their girlfriend's names*, and a bunch of other client type info. I have a V which shows the client's name, birthday, and maybe two other properties.
I would consider using that VM for that V, this illustrates my point that the V doesn't have to show all the info contained within the VM. This concept becomes more apparent when you change the V (as in, do some maintenance and change the UI of the view, because someone has decided that they want a bunch of fields removed and now they want to represent the client's age as an image) - i can still use the same VM, and just change the V (i could use a ValueConverter to represent the age as an image, thus avoiding a change to the VM).
At what point would i stop using the current ClientViewModel, and write a new one that was more specific to the needs of the modified ClientView?
There is no clear cut answer to that - it depends on the amount of time i have available to do the changes, the amount of time available for testing, and the trade-off in complexity between using a full blown Client object for the VM, and writing a new leaner version of the Client object while still retaining the old one.
*that should be a collection of independant objects incorporated in the client object, but just work with me here it's a made up example :)
Related
I am new to Google App maker and I don't have a lot of experience with coding either (sorry :/). Since App maker is marked as low-coding app builder tool, I assumed it was not that hard to make a very simple app with it. However, for me it is.
I need to make a simple app for demonstrations purposes only (so Cloud SQL and other complex database solutions are not in my interest here). I want to make it using calculated models (correct me if I am wrong, calculated models are just temporary solutions, since apps need to have like real databases to be fully functional?).
My app is basically made of 2 datas: 1) Employees and 2) Departments
-> Fields for "Employees" are: First name, Last name and Department.
-> Field for "Departments" is just Department name.
My app is supposed to look like this:
1st page: Table with current employees that has a button to add new employee,
2st page: Table with all department names (e.g. marketing, finance...) that has a button to add new department name,
3rd page: Form that opens when I click on add new employee button in which I can insert their first name, last name and from drop down menu choose department,
4th page: Form that opens when I click on add new department button in which I can insert new department name.
5th page: Form (or some other widget, not sure here) that has option to insert first and last name in order to find out what department that employee is assigned to.
I tried to make first 4 pages, but I end up with forms that I cannot insert anything into them. 5th page is still too much for me.
I hope you understand my struggles and if you know how to do it please share your knowledge. Thank you very much!
Calculated models are kind of like SQL views - they are not necessarily for temporary solutions. Every time you load a calculated model the script you write under that model's datasource is ran. That script usually loads data from an external source (I.e. grabbing stock prices from an API, loading data from an external SQL server, or generating random placeholder data).
You could use the cloud SQL models for this application that you are building - your table with all department names that is supposed to be displayed in the second page could just be a cloud SQL table with one single field for a department name.
I suggest you work through the example apps so you can get a better understanding of how the different components work. Here is a link to one for you to get started.
In short, you're going to create a few models to store information (I suggest using cloud SQL as the calculated models will require code whereas cloud SQL is more plug and play through app maker's bindings). Before you create any pages try to lay out how your databases will look as that will dictate how you set bindings or program your scripts.
Asking to completely make what is essentially a combination of the tutorials already provided by Google is pretty counter intuitive - you should ask more specific questions in regards to implementation.
As for App Maker being a low-code environment, that's only partially true. For very, very simple apps (think glorified forms) you will need only a couple lines of code and can probably do everything through drag-and-drop. However, anything more complicated than a simple form will almost certainly require a good chunk of actual code. There are plenty of resources online to learn Javascript.
You might want to try a google partner like AppSynergy for building stuff like this. It might be overkil for what you need (or maybe not if you intend to build a lot more stuff).
I have a problem I'm trying to solve and I'm really not sure I'm, A) solving it the correct way, and B) able to do what I want.
I have a List Page that is a basically a summary table (transportation table) that has a record in it for every Sales, Purchase, and Transfer order that we will ship. With it is a pile of rolled up information and such that's common from the 3 sources. We use this table on a few list pages and link out to where we need to. This was all built by someone else, but I'm maintaining some parts around it.
I've gotten a request to have the preview pane on a summary table based list page show the lines from the source order. So, if a "sales order" is selected in the grid, show the lines in the preview pane for the "sales order" that was selected. Same for a purchase order and transfer order.
So, my idea, based on pure ignorance and not a ton of experience with Dynamics is that I would just swap out the preview pane based on the source order. The SalesTableListPagePreviewPane for instance has already been updated to work with linking to this summary table. So, I wanted to just change the part reference at runtime.
I've managed to get the FormRun on a list page interaction class from the datasource. I've managed to get a list of the parts via the PartList object. But, I have no idea how to continue on to actually swap out a part reference.
Am I heading down the correct path? Is this a completely wrong Dynamics AX pattern?
Your assumption, that you can dynamically (run-time) change the parts of the form, is wrong.
Listpages especially are quite static, the only code available through interaction classes. It has the benefit that a listpage can be easily deployed on Sharepoint Enterprise Portal.
You have several options:
Use 3 different listpages for each type of transport
Use a common relation table with 3 sub-tables (sales, purchase and transfer)
The last option will enable you to do an outer join on the 3 sub-tables.
The common relation table could be a union view, but I doubt it will perform well.
I am just starting out with mobile development and the data handling for Flex mobile applications seem to be plain horror. I have spent two days on it, tried about 10 different approaches and still can't find a clen working solution.
So i have a TabbedViewNavigatorApplication with many views and subviews. All of them should be able to access the same data that i want to store in a model (so basically they need to access the same model class to add, edit and retrieve some data from there).
I create one instance of a model, pass it as data to all view stacks
If i change something in one view stack and switch to another one, i see the changes and all is fine.
But if I change the model data in one view and restart the application, I see changed data in that view but if i switch to another view, it has the old (unmodified) model. I would assume that the model would be the same instance but apparently each view has its own "model" when saving persistance data.
So how do you manage shared model over all views ? Ideally i would create it once on the first app launch, and then just add / remove items from any view or subview.
Or do i need to use the SQLite for that ? In this case it seems i would need to fetch the data for each view each time a view changes to stay up-to-date with the current data in the database ?
Please help :)
I've learning ASP.Net and Entity Framework 4 by a practical example. To trial this, I'm using the example of User sending in devices for Repair. They create an account online, add in a set of Details (address, phone, fax etc), and create the return form (RMA) online.
The concept I am struggling with, is assigning Details to the Returns. A Return has a set of Details, one for contact, delivery and billing. These can be foreign keys to the Detail table, as shown below.
The problem is, that if a User edits their Details online, it will update the Details used on the Return. This is not the desired behaviour. The Return should uses the Details which were available at the time it was created.
The question is, how do you make the entity framework create a new Detail object, instead of updating the existing one. That is if the user updates Detail 23 with a new postcode, Detail 23 is not changed, instead a new Detail is created (i.e. 45). Detail 23 is removed from the User, and the new Detail 45 is added to the User. Whilst an existing RMA using Detail 23 is unaffected, meanings if you query the RMA you get the details which were supplied at the time it was created.
If on reading this question, you think the concept is flawed, and instead the DB should be designed differently (i.e. copying Detail data to columns in RMA table, or adding in a form of composite key to Detail table to create a history of revisions). I'm happy to listen to those wise words as well.
If you have complex data editing rules that are outside of the realm of basic CRUD, then you essentially have two choices with Entity Framework.
Give up on simple data binding and build your special handling into a business rule layer that sits between your GUI and your data layer (EF).
Give up the simplicity of a thin EF layer and put your special data handling rules into stored procedures and then set the CRUD procedures in your EF model to the stored procs you've defined.
Either way, you are making a compromise because no ORM, EF or otherise, can accomodate both "codeless" databinding and non-trivial CRUD processing. Pick the approach that suits your project and perferences the best. Some people can't live without databinding, some can't live with it. Some love stored procs and others loath them.
I am in the process of migrating an Access application to Sharepoint 2010 (Enterprise). I would like to use as much Sharepoint "out of the box" funcationality as possible, but I am not opposed to creating some Web Parts.
I am struggling with the design of the "master" table in this application. The application is used to track employee productivity. Daily, about 50 users access the application and basically enter how many "Widgets" they completed that day. There are about 30 types of these "Widgets" and they don't change very often.
The table is designed with individual columns for each of these Widgets. This makes creating the Reports very easy, since all you have to do is select all the fields from the table and dump the result set.
The downside to this approach is obvikously the fact that the schema is "hard coded" (static). I have been asked (in the sake of time) to just normalize the table as much as possible (with CustomerIDs, EmployeeIDs, etc), but keep all the "Widget" fields in there.
I had proposed that we create a Master Detail type relationship where the users would Add a Row (perhaps in a GridView), select the "Widgets" they created that day (from a drop down) and enter their quantity. They generally only make 1 - 3 types of Widgets per day.
The users hate this design and want me to give them a data entry form with ALL the widgets displayed so they can just click in the box (beside the Widget they created that day) and enter their qty and then click save.
I know I could still create this type of Data Entry Form with a Master-Detail type of relationship, but I am pretty sure I couldn't using the SP Out of The Box forms. I would probably have to create a Web Part with a GridView and just populate the GridView with all the possible Wisdgets, then let the user enter the proper Qty(s) beside each widget they are made that day. Once the form is submitted back, I would then have to go through it and find any Qtys that are valid Numbers and add a (child) detail record for that Master record. (The Master Record would contain date, employee, customer, etc. etc.) The "edit" form would also have to work in a similar way.
This is a pretty "ugly" solution and I was looking for an alternative.
If I can't come up with a good alternative (and convice my manager that the code won't be too difficult to maintain or add too much development time to the project to complete it on time) then I will have to bring over this ugly, existing schema with all its wasted space and have "hard coded" stuff thoughout the application. (For instance, if I provide them with a SharePoint View to see how many Widgets of a certain Type were created, I will have to "hard code" all those values in the Drop Down and "Sum" the correct/matching database column. YUK.
Another consideration is the reporting. Right now all the reports just contain a column on the report for every widget. To preserve the look of these reports (if I use a Master/Detail relationship) will require "fancier" queries (Stored Procedures) to buld the proper result set in a "columuar" format. (And I am not sure how I would tackle laying out the SharePoint Views of the data in a similar fashion.)
It certainly would be "easier" to just leave the schema as is (and have all that wasted space in the table). I just hate developing an application that anytime we need to add a new "Widget" to the application, we have to change the application in several places and rebuild. (Although, my manager isn't concerned about that, he just wants to push it out, ASAP...sigh...)
Any help/recommendations on how to do this type of application (specifically how to create the data entry forms and views) in SharePoint would be greatly appreciated!
Shayne
Have you looked at these ideas:
http://paulgalvinsoldblog.wordpress.com/2007/12/24/implementing-master-detail-relationships-using-custom-lists/
http://blogs.msdn.com/b/alexma/archive/2006/04/10/610934.aspx
In my opinion you should be storing the data in list rather than SQL server. If you decide to use SQL server, look at BCS to build Master child view.