I have quite a complex class that has three one-to-many relationships and two many-to-many relationships with other classes. What I would like to do is to enable the user to fill all the details one by one - in one step or even better in multiple steps (wizard).
My class is called PeriodicTask - user has to select one Server object (which represents SQL Server instance ) and depending on the selection I need to present the user with the ability to select which databases he wants to use ( the best option would be to use checkboxes). I don't really know how to achieve this.
I would start with creating an action that returns JSON with databases for the selected server. It'll be invoked by jQuery. So far so good, but what to do then?
Should I add <input type="checkbox"> to the form for every database or maybe create another form and post to some other action? How to parse that when the form is submitted? Can I split it somehow into smaller steps ? HTTP is stateless so I somehow need to pass or remember the data that was previously submitted - how?
PS> I'm using Entity Framework here, so part of the class hierarchy is as follows:
You could do it like this:
User selects server instance from
dropdownlist.
After selection dropdownlist fires "change "event, handler of
which loads databases list to form using ajax (your action can provide JSON or html with checkboxes)
User selects checkboxes and presses
submit button
On submit you collect
checked item and post to action
using javascript
I would look at creating helpers for each of the options that would be self contained, they could maintain the state themselves.
Another cool option would be to create a tree view, where the root level is your server and next level is database. Load the data into a ViewModel so that it can be used as the data source for a tree view. It seems like a nice interface for what you have.
Believe it or not the Microsoft site is a great place to start when learning MVC
http://www.asp.net/mvc
Related
Is it possible to have 1 input text field that accepts characters from the user, and as the user types, queries to a webservice are launched, and to update the contents of another component dynamicaly with the results of the webservice (which would be a table below the input text)?
If you prefer to use Wicket form controls and Data Table component then you need to make the call to the REST service in your impl of IDataProvider.
Otherwise, as I explained to you earlier today in your other SO post you can do this directly in JS without Wicket. It is a matter of taste and skills.
I am in the process of modifying forms to account for V9 of Dynamics which is being rolled out currently.
Our environment is using Dialogs but these are being deprecated with V9 which means we have to prepare the forms to be used instead of these Dialogs.
Due to how fragmented our solution is the data is all over the place in different entities and can all be written too at different times.
Is it possible to have multiple entities/records on the same form which are all editable? This way I can run rules to hide and show as people edit specific fields.
From what I can identify, there is no "true" way to achieve this. However, if there are entities which are linked via a relationship within the solution, it is possible to add the "Party List" type field to the form and this will act as the link between the two entities. When you go to search for an existing record within the related entity, there is a new button which allows you too create a new record of that entity which directly associated with the form you were working on initially.
We do have editable subgrids. Add the subgrids of related entities & allow users to edit the related records in main record form at one shot.
I have a working system that lets me build a database containing instances of various entities , all linked together nicely.
Before I knew I would care, I came across a tutorial on using Core Data and bindings, and it went through a complete case where you get a table showing all the entities of some type with a column for each property. It showed both the UI side and the Data model side - not that I need the data model part at this point. Now, darned if I can find it. This is one of those things that is supposed to be easy, and requires virtually no code, but getting exactly the right connections in UIBuilder is not going to happen if I can't find instructions.
Also, I thought I came across an example of something like a query editor where the user could select which properties to sort on, which to match on, etc. Did I imagine that?
Anyone out there know where I can find such?
Sure, you can do this without code:
Add an array controller to your nib.
Bind or connect an outlet for its managed object context
Set the array controller to Entity mode, fill in the entity name, and select Prepares Content.
Bind your table view columns to array controller's arranged objects, and fill in the key name for the model key.
Regarding the query editor, open up the model, and on the Editor menu click Add Fetch Request.
I found at least a partial answer to the query editor question, in this apple tutorial. Not sure how far it will get me, as I prefer to write code where possible, since then I can leave a trail of comments.
I have a web application built on an MVC design.
I have a database which contains a large number of objects (forum threads) which I can't load into memory at once. I now want to display (part of) this collection with different filters in effect (kinda like what stackoverflow does with questions sorted by date, votes, tags etc).
Where do I implement the filtering logic? It seems to me that this must go into the model part of the application, as only models interact with the database (in my implementation). If I make the filtering a part of the view, then the view must access the database directly to get the list of filtered objects, right? I'd like to avoid this, because it exposes the database layout to the view. But at the same time, displaying different views of the same data should be implemented in the view part of the application, as they are just that -- different views of the same data.
So how do I resolve this? Do I create an additional model, say, FilteredThreadsList, and have it remember the filter to use, and then use a FilteredView to display the list of threads that FilteredThreadsList spits out?
Or do I have to build a ThreadQueryier that allows views to query the database for certain thread objects, so I can have the filtering logic in a view without exposing the database backend?
You should never query data from the view. I don't know what framework you are using in particular but as for Ruby on Rails (should be the same for other frameworks) we always pull the necessary data from the controller and store all that information into a variable. The variable will be accessed by the view which can help you avoid querying your database directly from the view.If the code to query the database gets too lengthy in the controller, insert that code into the model instead so it's more maintainable for your project in the future. Additionally, you can call this model method from multiple places in your application if needed. Good luck!
From an architectural point of view, the model should be having the code for filtering. This is so, because in many applications the code for filtering is not trivial and has a good amount of domain logic in it. (Think of filtering top gainers from a list of stocks). From your example as well, it looks the same since you might want to filter by vote or by date or by tags and then by answered or unanswered etc.
In some very simple applications that deal with search/list of entities and allows Create/Read/Update/Delete of an entity, the pagination, sorting and filtering logic is usually very generic and can be implemented in a controller base class that is inherited by all entity-specific controller classes.
The bottom line is this: if your filtering logic is generic put it in the controller else put it in the model.
Model, that's only bunch of entities.
View provides a visual representation of the data from model - use as much of views as you want. If your application is web based, you can fetch data into browser just once (AJAX) using and re-use them for different UI components rendered in the browser.
As for what entities and what view to use for their representation, I think it's work of Controller. If you need some support for it on "model layer", add it but avoid tight coupling.
I have having a little trouble wrapping my head around the design pattern for MVC when the data type of the model property is very different than what I wish to display in a form. I am unsure of where the logic should go.
Realizing that I am not really sure how to ask the question I think I will explain it as a concrete example.
I have a table of Invoices with a second table containing the InvoiceDetails. Each of the InvoiceDetail items has an owner who is responsible for approving the charge. A given invoice has one or more people that will eventually sign off on all the detail rows so the invoice can be approved. The website is being built to provide the approval functionality.
In the database I am storing the employee id of the person who approved the line item. This schema provides me a model with a String property for the Approved column.
However, on the website I wish to provide a CheckBox for the employee to click to indicate they approve the line item.
I guess my question is this -- how do I handle this? The Model being passed to the View has a String property but the form value being passed back to the Controller will be of the CheckBox type. I see two possible ways...
1) Create a new Model object to represent the form fields...say something like FormInvoiceDetails...and have the business logic query the database and then convert the results to the other type. Then after being submitted, the form values need to be converted back so the original Model objects can be updated.
2) Pass the original InvoiceDetails collection to the View and have code there create render the CheckBox based on the value of the String property. I am still not sure how to handle the submission since I still need to map back the form values to the underlying database object.
Maybe there is a third way if not one of these two approaches?
To make the situation a bit more complicated (or maybe it doesn't), I am rendering the form to allow for the editing of multiple rows (i.e. collection).
Thanks for any insight anybody can provide.
You need a ViewModel, like #Justn Niessner suggests.
Your controller loads the complete model from the database, copies just the fields it needs into a ViewModel, and then hands the ViewModel off to the view for rendering.
I'd use Automapper to do the conversion from Model to ViewModel. It automates all the tedious thingA.x = thingY.x; code.
Here is an additional blog post going over in detail the use of ViewModels in the Nerd Dinner sample.
I believe what you are looking for is the ViewModel.
In cases where you are using a ViewModel, you design the ViewModel to match the exact data you need to show on your page.
You then use your Controller to populate and map your data from your Model in to your ViewModel and back again.
The Nerd Dinner ASP.NET MVC Example has some very good examples of using ViewModels.