Tuesday, June 12, 2012

Know The 3 Model-View-Whatever UI Design Patterns MVC MVP MVVM!




  1. You Need To Know These 3 UI Design Patterns MVC MVP MVVM!

     Model-view-controller MVC The model–view–controller framework separates the representation of information in a computer program from the user's interaction with it.[1][2] The model consists of application data and business rules, and the controller mediates input, converting it to commands for the model or view.[3] A view can be any output representation of data, such as a chart or a diagram. Multiple views of the same data are possible, such as a pie chart for management and a tabular view for accountants.
    §  Model-view-presenter MVP is a user interface design pattern derived from MVC engineered to facilitate automated unit testing and improve the separation of concerns in presentation logic
    Model View ViewModel MVVM was designed to make use of data binding functions in WPF to better facilitate the separation of view layer development from the rest of the pattern by removing virtually all GUI code (“code-behind”) from the view layer

    Model–view–presenter - Wikipedia, the free encyclopedia

    en.wikipedia.org/wiki/Model–view–presenter
    Jump to Pattern description‎: MVP is a user interface design pattern engineered to facilitate automated unit testing and improve the separation of concerns ...
    Model–view–presenter
    From Wikipedia, the free encyclopedia
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    Model–view–presenter (MVP) is a derivative of the model–view–controller(MVC) software pattern, also used mostly for building user interfaces.
    In MVP the presenter assumes the functionality of the "middle-man" (played by the controller in MVC). Additionally, the view is responsible for handling the UI events (like mouseDown, keyDown, etc.), which used to be the controller's job. Eventually, the model becomes strictly a domain model.
    Contents
      [hide
    ·         1 Pattern description
    ·         2 History
    ·         3 Implementation in .NET
    ·         4 Implementation in Java
    ·         5 See also
    ·         6 References
    ·         7 External links
    [edit]Pattern description
    MVP is a user interface design pattern engineered to facilitate automated unit testing and improve the separation of concerns in presentation logic:
    §  The model is an interface defining the data to be displayed or otherwise acted upon in the user interface.
    §  The view is an interface that displays data (the model) and routes user commands (events) to the presenter to act upon that data.
    §  The presenter acts upon the model and the view. It retrieves data from repositories (the model), and formats it for display in the view.
    Normally, the view implementation instantiates the concrete presenter object, providing a reference to itself. The following C# code demonstrates a simple view constructor, where ConcreteDomainPresenter implements the IDomainPresenter interface:
    public class DomainView: IDomainView
    {
        private IDomainPresenter domainPresenter;

        public DomainView()   // Constructor
        {
            this.domainPresenter = new ConcreteDomainPresenter(this);
        }
    }
    The degree of logic permitted in the view varies among different implementations.
    At one extreme, the view is entirely passive, forwarding all interaction operations to the presenter. In this formulation, when a user triggers an event method of the view, it does nothing but invoke a method of the presenter which has no parameters and no return value. The presenter then retrieves data from the view through methods defined by the view interface. Finally, the presenter then operates on the model and updates the view with the results of the operation.
    Other versions of model-view-presenter allow some latitude with respect to which class handles a particular interaction, event, or command. This is often more suitable for web-based architectures, where the view, which executes on a client's browser, may be the best place to handle a particular interaction or command.
    From a layering point of view, the presenter class might be considered as belonging to the application layer in a multilayered architecture system with common layers but it can also be seen as a presenter layer of its own between the application layer and theuser interface layer.
    [edit]History
    The model-view-presenter software pattern originated in the early 1990s at Taligent, a joint venture of AppleIBM, and HP, and was the underlying programming model for application development in Taligent's C++-based CommonPoint environment. The pattern was later migrated by Taligent to Java and popularized in a paper by Taligent CTO Mike Potel.[1] After Taligent's demise in 1997, Andy Bower and Blair McGlashan of Dolphin Smalltalk adapted the MVP pattern to form the basis for their Smalltalk user interface framework.[2] In 2006,Microsoft began incorporating MVP into their documentation and examples for user interface programming in the .NET framework.[3] The evolution and multiple variants of the MVP pattern, including the relationship of MVP to other design patterns such as MVC, were analyzed in detail in an article by Martin Fowler[4] and another by Derek Greer[5]
    [edit]Implementation in .NET
    The .NET environment supports the MVP pattern much like any other development environment. The same model and presenter class can be used to support multiple interfaces, such as an ASP.NET Web application, a Windows Forms application, or a Silverlightapplication. The presenter gets and sets information from/to the view through an interface that can be accessed by the interface (view) component.
    In addition to manually implementing the pattern, a model-view-presenter framework may be used to support the MVP pattern in a more automated fashion. Below is a list of such frameworks under the .NET platform.
    [edit]Frameworks
    §  Claymore
    [edit]Implementation in Java
    In a Java (AWT/Swing/SWT) application, the MVP pattern can be used by letting the user interface class implement a view interface.
    The same approach can be used for Java web-based applications since modern Java component-based web frameworks allow development of client side logic using the same component approach as thick clients.
    Implementing MVP in Google Web Toolkit requires only that some component implement the view interface. The same approach is possible using the Echo2 web framework.
    MVP can be implemented in Java SE (Swing and AWT) applications using the Biscotti framework.
    [edit]Frameworks
    §  Echo2
    §  JFace
    §  Swing
    §  Vaadin
    §  ZK
    [edit]See also
    [edit]References
    6.     ^ Large scale application development and MVP from GWT project's web site. It explains how to use MVP within GWT.

    Model View ViewModel
    From Wikipedia, the free encyclopedia
    The Model View ViewModel (MVVM) is an architectural pattern used in software engineering that originated from Microsoft as a specialization of the presentation model design pattern introduced by Martin Fowler.[1] Largely based on the model–view–controllerpattern (MVC), MVVM is targeted at modern UI development platforms which support Event-driven programming, such as HTML5,[2][3]Windows Presentation Foundation (WPF), Silverlight and the ZK framework.
    MVVM facilitates a clear separation of the development of the graphical user interface (either as markup language or GUI code) from the development of the business logic or back end logic known as the model (also known as the data model to distinguish it from the view model). The view model of MVVM is a value converter[4] meaning that the view model is responsible for exposing the data objects from the model in such a way that those objects are easily managed and consumed. In this respect, the view model is more model than view, and handles most if not all of the view’s display logic (though the demarcation between what functions are handled by which layer is a subject of ongoing discussion[5] and exploration). The view model may also implement a mediator pattern organising access to the backend logic around the set of use cases supported by the view.
    MVVM was designed to make use of data binding functions in WPF to better facilitate the separation of view layer development from the rest of the pattern by removing virtually all GUI code (“code-behind”) from the view layer.[6] Instead of requiring user interface (UXi)developers to write GUI code, they can use the framework markup language (e.g., XAML) and create bindings to the view model, which is written and maintained by application developers. This separation of roles allows interactive designers to focus on UX needs rather than programming or business logic, allowing for the layers of an application to be developed in multiple work streams for higher productivity. Even when a single developer works on the entire code base a proper separation of the view from the model is more productive as the user interface typically changes frequently and late in the development cycle based on end-user feedback.
    Contents
      [hide
    ·         1 History
    ·         2 Pattern description
    ·         4 Timeline
    ·         5 Criticism
    ·         6 Open source MVVM frameworks
    ·         7 Free MVVM frameworks
    ·         8 Commercial MVVM frameworks
    ·         9 Java MVVM frameworks
    ·         10 See also
    ·         11 References
    ·         12 External links
    [edit]History
    Microsoft MVP Josh Smith reported[6] that
    "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."
    The MVVM pattern was conceived to support WPF and Silverlight, both pieces that debuted with the .NET Framework 3.0 which was released on 21 November 2006. This pattern is now being more broadly applied in other technology domains, much as happened with the earlier MVC or Model View Presenter (MVP) patterns.
    Several Microsoft architects working on WPF have written extensively about MVVM in online media, including creator John Gossman, Microsoft MVP Josh Smith, and Microsoft Program Manager Karl Shifflett.
    As the understanding of the pattern disseminates through the industry, discussion continues regarding what tools can be developed to support the pattern, selection of where to place different kinds of supporting code in the pattern, the best methods for data binding, and how to expose data within the view model, how appropriate the pattern is for use within JavaScript, and other topics.
    More recently the pattern has been described as model-view-binder (MVB) when implemented outside of the Microsoft stack.[7]
    [edit]Pattern description
    Broadly speaking,[6][8][9] the model-view-view-model pattern attempts to gain both the advantages of separation of functional development provided by MVC as well as leveraging the advantages of data bindings and the framework by binding data as far back (meaning as close to the pure application model) as possible while using the binder, view model, and any business layer’s inherent data checking features to validate any incoming data. The result is that the model and framework drive as much of the operations as possible, eliminating or minimizing application logic which directly manipulates the view (e.g., code-behind). Whilst the pattern was pioneered at Microsoft, as a pure concept it is independent of any given implementation. As such the pattern can be used in any language and with any presentation framework which provides a declarative data binding capability.
    Elements of the MVVM pattern include:
    Model: as in the classic MVC pattern, the model refers to either (a) a domain model which represents the real state content (an object-oriented approach), or (b) the data access layer that represents that content (a data-centric approach).
    View: as in the classic MVC pattern, the view refers to all elements displayed by the GUI such as buttons, labels, and other controls
    View model: the view model is a “model of the view” meaning it is an abstraction of the view that also serves in mediating between the view and the model which is the target of the view data bindings. It could be seen as a specialized aspect of what would be a controller (in the MVC pattern) that acts as a converter that changes model information into view information and passes commands from the view into the model. The view model exposes public properties, commands, and abstractions. The view model has been likened to a conceptual state of the data as opposed to the real state of the data in the model.[10] The term "View model" is a major cause of confusion in understanding the pattern when compared to the more widely implemented MVC or MVP patterns. The role of the controller or presenter of the other patterns has been substituted with the framework binder (e.g., XAML) and view model as mediator and/or converter of the model to the binder.
    Controller: some references for MVVM also include a controller layer or illustrate that the view model is a specialized functional set in parallel with a controller, while others do not. This difference is an ongoing area of discussion regarding the standardization of the MVVM pattern.
    Binder: the use of a declarative databinding and command bind technology is an implicit part of the pattern. Within the Microsoft stack this is the XAML technology.[11] Essentially this architectural component frees the developer from being obliged to write boiler plate logic to synchronise the view model and view. It is the organisation of code to make best use of this capability which distinguishes the pattern from both MVC and MVP. When implemented outside of the Microsoft stack the presence of a declarative databinding technology is a key enabler of the pattern.[12][7]
    [edit]An implementation of the view model
    Snippet: here a simple implementation of the pattern realized using TDD (test-driven development) on WPF How to implement MVVM (Model-View-ViewModel) in TDD, on Code MSDN.
    An implementation of the view model in C#.
    public class CustomerViewModel
            : ViewModelBase<CustomerViewModel>
    {
            private readonly IDialogService dialogService;
            private Customer currentCustomer;
            private int i;

            public CustomerViewModel()
            {
                    CustomerList = new ObservableCollection<Customer>();
                    AddNewCustomer = new RelayCommand(PerformAddNewCustomer);
            }

            public CustomerViewModel(IDialogService dialogService)
                    : this()
            {
                    this.dialogService = dialogService;
            }

            public Customer CurrentCustomer
            {
                    get { return currentCustomer; }

                    set { SetProperty(ref currentCustomer, value, x => x.CurrentCustomer); }
            }

            public ObservableCollection<Customer> CustomerList
            {
                    get;
                    private set;
            }

            public ICommand AddNewCustomer { get; private set; }

            private void PerformAddNewCustomer()
            {
                    CustomerList.Add(new Customer { Name = "Name" + i });
                    i++;

                    if (dialogService != null)
                    {
                            dialogService.Show("Customer added");
                    }
            }
    }
    Snippet: here a simple implementation of the pattern realized in Java using the ZK framework from the ZK ToDo2 patterns demo application:
    public class ZkToDoViewModel  {

            protected ReminderService reminderService;

            public void setReminderService(ReminderService reminderService) {
                    this.reminderService = reminderService;
            }

            protected ListModelList<Reminder> reminders = new ListModelList<Reminder>();

            public ListModelList<Reminder> getReminders() {
                    List<Reminder> rs = this.reminderService.findAll();
                    this.reminders.clear();
                    this.reminders.addAll(rs);
                    return this.reminders;
            }

            protected Reminder selectedReminder = new Reminder();

            public Reminder getSelectedReminder() {
                    return this.selectedReminder;
            }

            @NotifyChange
            public void setSelectedReminder(Reminder reminder) {
                    this.selectedReminder = reminder;
            }

            @Command
            @NotifyChange({"reminders","selectedReminder"})
            public void delete() {
                    if( this.selectedReminder.getId() != null ){
                            try {
                                    this.reminderService.delete(selectedReminder);
                                    this.selectedReminder = new Reminder();
                            } catch (EntityNotFoundException e) {
                                    // no doubt someone else deleted it at the same time. nothing to do.
                            }
                    }
            }

            @Command
            @NotifyChange({"reminders","selectedReminder"})
            public void save() {
                    if( this.selectedReminder.getId() != null ){
                            try {
                                    this.reminderService.merge(selectedReminder);
                            } catch (EntityNotFoundException e) {
                                    // hum. some else deleted this. should really send this
                                    // up to the user and ask them to reload the page.
                                    e.printStackTrace();
                            }
                    } else {
                            this.reminderService.persist(this.selectedReminder);
                    }
            }

            @Command
            @NotifyChange({"reminders","selectedReminder"})
            public void create() {
                    this.selectedReminder = new Reminder();
            }
    }
    [edit]Timeline
    - November 2010 - The Microsoft patterns & practices team published guidance on using MVVM, under the name Prism v4.
    [edit]Criticism
    A criticism of the pattern comes from MVVM creator John Gossman himself,[13] who points out that the overhead in implementing MVVM is “overkill” for simple UI operations. He also states that for larger applications, generalizing the View layer becomes more difficult. Moreover, he illustrates that data binding, if not managed well, can result in considerable memory consumption in an application.
    [edit]Open source MVVM frameworks
    §  IaxiomI. "Carbon MVVM".
    §  IdeaBlade. "Cocktail".
    §  Josh Smith. "MVVM Foundation".
    §  Sacha Barber. "Cinch".
    §  Daniel Vaughan. "Calcium SDK".
    §  Karl Shifflett. "Ocean".
    §  Tony Sneed. "Simple MVVM Toolkit".
    §  Laurent Bugnion. "MVVM Light Toolkit".
    §  Eye.Soft. "Hyperion SDK".
    §  Lester Lobo. "CoreMVVM".
    §  Paul Betts. "ReactiveUI".
    §  Rob Eisenberg. "Caliburn".
    §  Rob Eisenberg. "Caliburn Micro".
    §  William e Kempf. "Onyx".
    §  Peter O’Hanlon. "GoldLight".
    §  Michael L Perry. "Update Controls".
    §  Steve Sanderson. "KnockoutJS".
    §  Geert van Horrik. "Catel".
    §  Jeremy Likness. "Jounce".
    §  Xomega.Net. "Xomega Framework".
    §  Marcus Egger, EPS Software. "Code Framework".
    §  Volkov V.S. "Mugen MVVM Toolkit".
    §  Riana Rambonimanana. "Lakana".
    [edit]Free MVVM frameworks
    §  2sky (Visual Studio Partner). "Vidyano".
    [edit]Commercial MVVM frameworks
    §  Intersoft Solutions (Visual Studio Partner). "ClientUI".
    §  MVVM framework for Unity 3D. "NData / EZData / iData".
    [edit]Java MVVM frameworks
    §  Potix. "ZK".
    [edit]See also

  2. Design PatternsModel View Presenter

    msdn.microsoft.com/en-us/magazine/cc188690.aspx
    The MVP pattern helps you separate your logic and keep your UI layer free of clutter. This month learn how.
  3. Model-View-Presenter Pattern

    msdn.microsoft.com/en-us/library/ff647543.aspx
    How to: Implement the Model-View-Presenter Pattern. How to: Unit Test a Presenter. Model-View-Presenter QuickStarts. Separator. Expand Minimize. MSDN ...
  4. MVC or MVP Pattern – Whats the difference? - Todd Snyder ...

    blogs.infragistics.com › Blogs › Todd Snyder
    Oct 17, 2007 – The MVP pattern is a UI presentation pattern based on the concepts of the MVC pattern. The pattern separates responsibilities across four ...
  5. Retirement note for Model View Presenter Pattern

    martinfowler.com/eaaDev/ModelViewPresenter.html
    Jul 11, 2006 – Retirement note for Model View Presenter Pattern. Last significant update: 11 Jul 06. Upon further study and reflection, I decided that pattern ...
  6. Dot Net Facts: The MVP pattern

    dotnetfacts.blogspot.com/2009/10/mvp-pattern.html
    Oct 19, 2009 – The MVP pattern. The MVP stands for Model-View-Presenter and it is a user interface (UI) design pattern engineered to facilitate automated unit ...
  7. Everything You Wanted To Know About MVC and MVP But Were ...

    haacked.com/.../everything-you-wanted-to-know-about-mvc-and-mv...
    Jun 15, 2008 – Many consider the MVP pattern to simply be a variant of the MVC pattern. The key difference is suggested by the problem that the MVP pattern ...
  8. Model View Presenter with ASP.NET - CodeProject

    www.codeproject.com › ... › Design and Architecture › General
     Rating: 4.9 - 185 reviews
    Jul 2, 2006 – This article describes using the Model-View-Presenter pattern within ASP.NET 2.0 to encourage proper separation of concerns between ...
  9. Model View Presenter (MVP) design pattern close look – Part 2 ...

    blog.vuscode.com/.../model-view-presenter-mvp-design-pattern-clos...
    Nov 4, 2007 – If you are new to Model View Presenter pattern at all, you should check the Model View Presenter entry level post which explains the most ...
  10. The MVP Pattern

    www.dsoftworld.com/2011/03/mvp-pattern.html
    MVP is a derivative of MVC aimed at providing a cleaner separation between the view, the model, and the controller. The most relevant change from MVC is that ...

starts like this:


MVC or MVP Pattern – Whats the difference?

Over the years I have mentored many developers on using design patterns and best practices. One question that keeps coming up over and over again is: What are the differences between the Model View Controller (MVC) and Model View Presenter (MVP) patterns? Surprisingly the answer is more complex than what you would suspect. Part of reasons I think many developers shy away from using either pattern is the confusion over the differences.
Before we dig into the differences let’s examine how the patterns work and the key benefits to using either one. Both (MVC & MVP) patterns have been use for several years and address a key OO principal namely separation of concerns between the UI and the business layers. There are a number of frameworks is use today that based on these patterns including: JAVA StrutsRORMicrosoft Smart Client Software Factory (CAB)Microsoft Web Client Software Factory, and the recently announced ASP.Net MVC framework.
Model View Controller (MVC) Pattern
The MVC pattern is a UI presentation pattern that focuses on separating the UI (View) from its business layer (Model). The pattern separates responsibilities across three components: the view is responsible for rending UI elements, the controller is responsible for responding to UI actions, and the model is responsible for business behaviors and state management. In most implementation all three components can directly interact with each other and in some implementations the controller is responsible for determining which view to display (Front Controller Pattern),
Model View Presenter (MVP) Pattern
 
The MVP pattern is a UI presentation pattern based on the concepts of the MVC pattern. The pattern separates responsibilities across four components: the view is responsible for rending UI elements, the view interface is used to loosely couple the presenter from its view, the presenter is responsible for interacting between the view/model, and the model is responsible for business behaviors and state management. In some implementations the presenter interacts with a service (controller) layer to retrieve/persist the model. The view interface and service layer are commonly used to make writing unit tests for the presenter and the model easier.


and the punch line:


Here are the key differences between the patterns:

·         MVP Pattern
o    View is more loosely coupled to the model. The presenter is responsible for binding the model to the view.
o    Easier to unit test because interaction with the view is through an interface
o    Usually view to presenter map one to one. Complex views may have multi presenters.

·         MVC Pattern
o    Controller are based on behaviors and can be shared across views
o    Can be responsible for determining which view to display (Front Controller Pattern)


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