Can anyone direct me towards some code or a tutorial for implementing the ViewModel in Flex 3?
All I'm finding on the web are examples for Silverlight.
Martin Fowler has also written about these ideas in the past under the term "Presentation Model". So you might find useful tutorials under that search phrase as well since it's not an "MS invented term". :-)
Indeed, this MS overview material acknowledges Fowler's work directly
In 2005, John Gossman, currently one
of the WPF and Silverlight Architects
at Microsoft, unveiled the
Model-View-ViewModel (MVVM) pattern on
his blog. MVVM is identical to
Fowler's Presentation Model, in that
both patterns feature an abstraction
of a View, which contains a View's
state and behavior. Fowler introduced
Presentation Model as a means of
creating a UI platform-independent
abstraction of a View, whereas Gossman
introduced MVVM as a standardized way
to leverage core features of WPF to
simplify the creation of user
interfaces. In that sense, I consider
MVVM to be a specialization of the
more general PM pattern, tailor-made
for the WPF and Silverlight platforms.
I wanted to share a comparison I wrote up of MVVM (Silverlight) vs PresentionModel (Flex). It shows how the two implementations of the same pattern differ/compare:
http://houseofbilz.com/archives/2010/12/29/cross-training-in-silverlight-flexmvvm-vs-presentation-model/
The reason all of the examples your finding are for Silverlight is because MVVM is by-and-large a Microsoft invention. It has to do with the ease of tying WPF views with data. The "ViewModel" is little more than a way of describing a subset of functions performed by the Controller in a traditional MVC design model; some MVVM descriptions even include a controller.
With that said, it doesn't really matter whether your app follows the MVVM or MVC models precisely. It's more of a high-level, organizational idea that should guide your design and development. If you're totally clueless about the models you can find any number of quickie web tutorials, and probably some printed literature on the subject.
Related
I recently worked at HP doing several ASP.NET MVC3 projects as I came from a software background I was relatively new to the inner workings of MVC3 as well as the best practices.
During this time I somewhat adapted the coding style of fellow co-workers and ways of designing my pages that I still stick with to this day. With all of this in mind my main question is what would anyone recommend for learning material; books/videos/tutorials. I can learn from any of those resources and I would love to know that I am coding properly.
I have several projects under my belt and many large scale business solutions that I have coded using Razor and ASP.NET but there are times where I feel that what I am doing is either very hacky or just an inefficient way of coding things. The larger the project is the more difficult it becomes to add new features because of this.
I think this is my lack of experience in coding but at the same time I would like to overcome this and I feel that with the mass experience I do have with MVC3 I could adapt to a easier style or design pattern that would help me not only optimize my code but become a much better web developer. If anyone has any suggestions on books or training sites or anything please let me know as I would love to get better.
Thanks in advance to anyone that has been in my shoes and is willing or capable of recommending anything!
I was dealing with the same issue and found it useful to make a mind map. While it's impossible to give you a full understanding, I can try point you in the right direction with some basic ideas.
download/view (http://www.xmind.net/share/highroad/mvc3-design-pattern/)
Are you familiar with design patterns? Well they exists with MVC applications too :)
If you want to talk the talk and understand what people including myself are talking about, you would need to know the typical design patterns that come with building what they call enterprise level applications. These design patterns are the only real way to begin to understand the concepts.
These patterns structure complex business logic in ways that have become the tried and tested solutions (design patterns) to the design challenges the developer's face.
In the diagram notice there are 3 main layers:
Presentation Layer
Business Logic Layer
Data Access Layer
Some of the highly used design patterns when dealing with Model View Controller in ASP.NET include:
Business Logic Layer Design Patterns:
Active Record. Models relate exactly to the database like in lightweight frameworks e.g. Ruby on Rails). When creating new MVC3 application with ASP.NET and scaffolding views and controllers, this is how it sets it up. Is perfect for less complex applications. So why not just use Ruby on Rails? I would
Domain Logic Layer. Uses MVC with the controller containing very little code and create lots of extra models that can do complex logic, the MVC is only for presentation. Often with this style of layer, a lightweight layer called a Service Layer can be used to call all the functions in the Domain Layer from the controllers i.e. the controller calls the method in the Service Layer class which calls the domain layer. This design pattern seems to be very popular with people who enjoy object oriented programming. See link below to my (quite basic) project designed using Domain layer.
Transaction Script - Use the controller to do a lot of the logic work per action, the problem is a lot of actions need to do the same things so there will be code repetition
For the Data Access Layer:
Something like entity framework models combined with a repository which can perform any SQL queries you need.
Not going into all the patterns for this layer but they include: Data Mapper
With simple apps, there is no real data access layer, it only becomes necessary if you use the Domain Layer in the business layer (which usually is the case)
Depending on what structure your application takes, your Models will mean very different things. In general they will not be models linked to the database (the default when creating a new app makes them like this). Instead they will be ViewModels which are only responsible for holding data that each of the views will need.
I have created a ssample app which you can see here.
https://github.com/testbrian/enterpriseframeworksB
I don't know if this is an example of an enterprise solution, but I have learned a lot from the techniques found in RaccoonBlog. I like how the Layout.cshtml and other razor files use RenderAction to modularize the views.
The project is an example of MVC3 using RavenDb, but it's also one of the best real world applications I've seen since it's actually used in production.
Hope this helps.
From last few days i have been searching the optimal architecture for my new web application, which would be devloped in ASP.Net using C#. Until now, i only find and study following 3
Three Tier Architecture (Note: By
Tier i mean logical layer)
Model View Controller (MVC)
Model View Presenter (MVP)
Now folling are my questions:
1) As far as i understand 3 Tier Architecture and MVP can I say that MVP and 3 Tier are
the same thing? If not, then what is the difference bewtween both? (Note: I only find
the difference between MVC and MVP or MVC and 3 Tier Archi but no one adress the diff
between MVP and 3 Tier Archi)
2) I only discover above three architectural options, is there any other options
available too? (Note: Here i want only the options for overall architecture of web
application,like above 3)
From a software architecture perspective; we use terms because terms mean something. When you use a term like "3-tier", you should use it where it fits it's intended and understood meaning. All sorts of things could be deemed "3-tier" simply by virtue of having three discrete components of some sort. But, if you used that term to describe MVP, you'd be misleading the other person. Why not simply say "MVP"?
3-Tier generally refers to three physical tiers. And Wikipedia has a great article on it here.
With the associated diagram:
Neither MVP nor MVC exclude using these three physical tiers. In fact, simply coining your application as an "MVC" application (or "MVP") doesn't really clarify much anymore. For example, it could be MVC on the server side (as in ASP.NET MVC) or it could be MVC on the client side with Javascript, or both!
As far as your question about architectural options; the playing field is pretty wide-open. The choices you make typically depend on a number of factors which you should be collecting while you collect your application requirements.
Often times you must make a trade off between Scalability and Complexity. However, a number of new technologies are making this trade off negligible - and I'd advise anyone starting a new project to consider them seriously (some discussed below).
It's almost always best to have, physically, a dedicated data tier (SQL, Mongo, Azure, Amazon, take your pick), and a dedicated, scalable, logic tier (usually implemented these days as WCF services in .NET land).
Most times people join their website and logic tiers... but this doesn't have to be the case. Sometimes it makes sense to have a physical tier exclusively for web services which are only accessible by your web site tier. Again, it's all situation-dependent.
As far as logical layers go (within your logic tier) it's almost always best to have some sort of data access layer (DAL), an in-code model (whether implemented manually, or through something like LINQ-to-Entities), and a dedicated business logic layer.
More and more these days people seem to be falling back to classic HTML and Javascript (with the help of things like JQuery, Prototype, DOJO, etc.) and using REST/JSON to chat with web services for retrieving and displaying data on the client side. In this scenario you can have a full-blown application on the client side, and another full-blown application in your back end... each with their own implementations of the logical layers I described above.
Options are wide open.
My take on things:
3-tier is not the same as MVP/MVC.
Many folks interpret the "Model" as a very broad concept that could contain lots of behaviour (including domain logic). I don't. The model is what the view needs to render itself. Sometimes it may have behaviour but, once again, only for behaviour related to view rendering.
With MVP you have a 1-1 mapping between the View and the Presenter. Although conceptually you could have more in reality it probably won't turn out that way. The presenter is only concerned with mediating between other layers and the view.
With MVC there is in all probablity more than 1 view that the controller deals with since it is concerned with flow.
So MVC/MVP can be used together and are front-end related and are part of the n-tier architecture.
Hope that makes sense.
You will see in answers such as this What are MVP and MVC and what is the difference? That MVC and MVP are addressing the structure of the code concerned with UI. They address questions such as:
Which component understands the user's actions?
Which component decides what view to present next?
What is the relationship between View and Model?
Neither MVC nor MVP go into details of what's inside (or beneath) the Model. In some systems the Model is comparatively simple, just a thin skin on top of a database, in other systems there's an awful lot of logic down there, for example integration with Enterprise systems such as SAP and CICs.
In its traditional meaning a 3-tier architecture (or more generally an n-tier architecture) puts additional structure inside the Model.
This wikipedia article discusses MVC v n-tier architectures. I think it's reasonable to substitute MVP for MVC in this article.
As to your application's architecture: my perception is that modern apps tend to have a rich UI presented in the browser, using simple REST services supplied by a Model on some server and then some arbitrarily complex stuff in the model. I guess you can see this as an n-tier architecture. The interesting thing is that as you structure your Javascript (JQuery, Dojo or whatever) in teh browser you find design patterns coming out, and an MVC pattern actually can emerge purely in the presentation tier.
The DevExpress XAF does much basis work for you, it creates a database based on your business objects, and dynamically generates a UI based on these, with basic functions like add, delete, sort etc. already present.
This leaves me wondering how to go about properly designing and modelling an application built on this framework. I could only model my business objects, or I could identify functions provided by the framework and include them in a details model down to sequence diagram level, but so much is being done by 'external' calls that I feel I would be wasting valuable time.
I am hoping someone with experience modelling application designs for this specific framework can give me some advice on what areas I should focus on.
As for DC, as Leon mentioned above, it has many benefits compared to the regular persistent classes. If all goes according to plan, we will release the Domain Components technology in the near future, and resolve all the remaining issues with it.
If you feel that it is hard to learn, please let us know the most difficult parts you experienced. We will be glad to review them and possibly make the things easier for you and other users.
P.S.
I apologize for the delay in responding; I was on sick leave. You will receive more timely responses if you post your questions in the DevExpress Support Center.
#ProfK:
Am I correct that you are looking for something like visual designer for your business models?
If so, then I am afraid that XPO (XAF) does not currently provide such a functionality. However, you can use free third-party tools for modeling, such as Liekhus ADO.NET Entity Data Model XAF Extensions
I hope you find this information helpful.
I'm using XAF for almost two years now and I'm very happy with it. Developing an app is very quick, nice architecture, both Win and Web the same time and great UI. As with all frameworks, it has a learning curve, but if your already familiar with DevExpress controls that it's not very hard.
As Dennis mentioned, most behaviour can be overriden or extended. Regarding your modelling question, if think an important choice you have to make is whether or not you will use their Domain Components technology. Basically they have 2 ways: the old fashion way by inheriting from the XAF or XPO base classes or by using DC. DC allows a clean separation in modules and allows multiple inheritance. They can do that by generating classes runtime, but it still has some issues.
And the framework comes with a Business Class Library, a set of common classes which may be useful.
When I get stuck or cannot find the answer myself, I always use their fantastic Support Center. Most issues I ran into were already asked and answer on that site.
Briefly, each XAF application consists of Modules. There can be standard (system) and extra (user-defined) modules. Each Module can contain business objects, so-called Application Model customizations, Editors, Controllers, and Actions to provide additional business logic, customize UI and provide interaction between framework parts. You can model and customize your application on each level listed above, including but not limited by the underlying framework's metadata and data store ones. You can find more information about the framework's architecture here:
http://documentation.devexpress.com/#Xaf/CustomDocument2559
I should emphasize that it is possible to override behavior of almost every part of the framework. For instance, create your own editors for detail and list forms, override certain standard controllers, etc.
If you experience any further difficulties with our framework, feel free to contact us through our Support Center. We will be always glad to not only answer you questions, but advice a certain technical or design solution, provide some example code, etc.
i want to learn entity framework. i started with some EF tutorials and i also know little about linq to sql.
i want to learn through a pet project. project should be in three layers. web forms (prez), data layer(c# lib), bussiness layer(c# lib). Project can be any, any functionality. just want to learn how to use EF in diff. layers and in UI.
can anyone guide me how do i start to do layering? help me to learn how should i use EF objects from DAL layer to BL and then UI.
I am confused as all tutorials shows direct binding of EF to EF datasource in UI and with controls.
thanks a lot.
In order to maintain a layered architecture I would create partial classes of the generated EF Classes. In these classes I would have methods I could use with objectdatasources in the presentation layer. Thats how I do it anyways, hope it helps!
A couple of things I would recommend:
Rob Conery (with occasional guests) put together a video series on building a storefront site using ASP.NET MVC. He used LINQ-to-SQL, not Entity Framework, but I don't think the difference is significant to what you are interested in learning. One nice thing about this series is that he walks you through the various design decisions he makes, and even backtracks when he later feels that one of them was wrong. Another is that, in addition to MVC and LINQ-to-SQL, he also explores some other development concepts such as inversion of control and test-driven development.
Martin Fowler's book Patterns of Enterprise Application Architecture is a great resource for this sort of thing. He lays out the different patterns that are available in each tier of your application and discusses how to use them and when each is appropriate. Fowler's writing style is friendly and easy to read, and a lot of the patterns in his book are prominent in the vernacular of the software development world today (e.g. Repository pattern, Active Record, Unit of Work).
Hope this helps!
I have started using Presentation Model w/ ASP.NET webforms and like the pattern quite a bit. What I am really having an issue with is where to instantiate some of my classes, mostly the presentation model, my business object, and things like the data for drop down lists. So I could use some tips or a complete example of the Presentation Model (I have only find pieces so far).
Video Links -
Rik Bardof on Design Patterns (including MVP)
Jean Paul Boohdoo on MVP
As far as the rest of your architecture goes, I would recommend reading Jeffrey Palermo's blog series on Onion Architecture. He has a sample project CodeCampServer that illustrates some good practices. This is a web app using ASP.NET MVC, but the principles still apply.