I've done some research about this topic and i already used the MVVM pattern in few applications.
I'm asking this question because sometimes MVVM is referred as a design and sometimes as an architectural pattern.
In most of the cases, the MVVM Pattern is called a design pattern. However personally I would vote for architectural because for me it clearly defines the architecture of an application (eg. three layer, View, ViewModel, Model and how they interact with each other)
This SO Question & Answer is about the difference between architectural and design pattern. In the answer it is said that MVC is a architectural pattern. Almost every explanation of MVVM contains a comparison with MVC. Is MVVM therefore also an architectural pattern?
This msdn article (which is btw very good) calls the MVVM Pattern a design pattern and is written by someone who really should know the difference.
I'm confused. Design or architectural pattern? is the term just mixed up?
EDIT: i need to know this for my bachelor thesis
I tend to think of architectural patterns as "decisions" with a lasting ramifications. They make up the skeleton of your application and so it is hard to get away from them.
For instance, a methodology for how to build your views is very hard to get away from, so I'd call it an architectural pattern. Microsoft designed ASP.NET WebForms to work a lot like WinForms. It was difficult to switch to a more MVVM approach mid-way through a project. Even choosing WebForms as your technology stack drastically affected what you could do with your application.
I think of design patterns as variants of an implementation - they can be used without impacting the rest of the application. You typically refactor to patterns, with the expectation that the code will change. To the point, design patterns are meant to help facilitate future change.
Obviously there is a fuzzy line between the two. Consider the repository pattern (typically considered an architectural pattern). It is really a facade (or proxy) to your data tier. Here, you pointing out a recurring use of a design pattern - elevating it to an architectural pattern - because it affects how you architect your system. You now have a rule: whenever I hit the database, I will do this, this and this.
MVVM is the UI-related design pattern as per Microsoft. check below link
wpf-apps-with-the-model-view-viewmodel-design-pattern
Architectural patterns are at higher level than design patterns. Architectural patterns are high-level strategies that concerns large-scale components, the global properties and mechanisms of a system.
Or in more simplified term, Architectural pattern define the components involved in the system on a higher level, how are they assembled and organised, and how they communicate with each other.
Design patterns are usually associated with code level commonalities or can say it is on lower level which explains how the software/component is built.
Holistically :
Architectural patterns - fundamental structural organization for software systems **(Deals with separation of concern)
Design patterns - Deals with implementation level details in software/software component construction
Related
I spent short time studing Habanero and i found it good approach for making Enterprise Application in a really short period of time.
The pattern witch Habanero use is "Active Record" as it's developers say.
My questions are:
There any similar application like Habanero witch fully support Domain
Driven Design by determining aggregate roots, entities and value objects
Is it right decision to use such tools in big organizations
Does it worth training our team on such a tool
thank you
Framework support for Domain Driven Design is quite different from frameworks supporting data driven applications. Such framework should increase the productivity of developers that works with an ubiquitous language that evolves with the business and that is learned by a domain-expert.
They should not face concepts like aggregates, root, value objects because they are just modelling concepts, conceptual tools, but ways to ease the development process. Thus a framework exposing abstract classes or interfaces named AggregateRoot, Entity or ValueObject is fundamentally broken. It doesn't provides any real value to an application, just useless indirections.
However:
There are a few frameworks designed to support domain driven design, listed here. Moreover, I'm developing one by myself based on previous experiences that worked very well
It depends, obviosly. For example we used all of the Epic's modeling patterns with success.
We used some "home made" framewoks too, and some of them proved to really increase productivity. However, such frameworks (if useful) always have steep learning curves and it depends very much on how much reliable the software have to be and what are the developers skills.
It depends on the framework, on the complexity of the business (if you don't need a domain expert to understand it, you don't need DDD) and on the developers, too. I faced successful stories and huge failures with different frameworks in different contexts. I've also had a conference that faced the topic (you can see the slides here).
I have an iphone app which is a tabbar based application. What is the design pattern of my app. Sorry for asking a fundamental question, i am not aware of design pattern.
Tabbar doesn't imply any design pattern. It is just UI element that represent some data.
Your app can use several design patterns. For example for data representation it is probably MVC (model-view-controller) pattern.
Read this link. As you can see there are tons of patterns and they are almost always mixed in your app.
A design pattern is just a commonly found approach to commonly occurring problems in computer science. It's usually used in reference to object-oriented programming design patterns such as those described by the Gang of Four. We could not identify the specific design patterns you used without looking at your code as a whole.
I'm working on establishing automated testing practices and test suites in an organization. A peer is telling me that we "should use a framework". To me, a framework is any set of code and/or other tool that helps you create something.
My peer seems to be suggesting that there are industry standard automated testing frameworks.
I've seen the following patterns in designing Test systems before:
Data Driven
Keyword Driven
Model Driven
Query Driven
My counterpart includes "Modular" as one of these. Because of my background in Software Engineering, I hear the word "Modular" and think of modular programming (as opposed to object-oriented, aspect-oriented or procedural programming)... a way of organizing code, not a methodology or framework type in and of itself.
I've seen the wikipedia definition for "Modular Automation" and it looks the same as the programming paradigm.
What am I missing? What can I read to get on the same page as my counterpart? Is it me or him that doesn't understand something? I have over a decade of software engineering experience, my counterpart has been in QA for nearly that long. He's not able to site references. I've searched the google for 6 hours now trying to learn about this "Modular Framework" and can't find a technical example and nothing more than the standard programming paradigm (e.g. organize code into modules).
It turns out the major industry-standard designs for automated testing are:
Data Driven
Keyword Driven
Model Driven
Query Driven
Additionally, "hybrid" approaches are used. These are approaches in which more than one of the above designs are used.
In a number of places on the web (including wikipedia) "Modularity Driven" test case design is mistakenly referred to as if it were one of the automated test case design strategies listed above. The definition of this mistaken term ("Modularity Driven") appears to have more to do with the organizational aspects of coding than the way in which One drives an automated test. "Modularity Driven" automated testing is a misnomer (or mistaken term altogether). In other words, there is no such thing. The term "modular" describes the programming paradigm being used.
The modular aspect of a test is in its organization, storing code in modules as opposed to other programming paradigms like OOP, or Procedural, etc.
I have heard of Modular Automation also referred to as Component Based Test Case Design. HP is a big player in this space. The came up with a Product that is called Business Process Testing.
It consists of:
•Reusable Business Components
•Business Components converted into Business process test
Business components are reusable units that perform a specific task in a business process. (for example – Add to Cart)
A business process tests is a scenario comprising of business components (for example - Place an Order)
In HP's Quality Center the Business Components module enables you to create and manage reusable business components.
Then the Test Plan module enables you to drag and drop the components into business process tests, and debug the components.
I was trying to find an answer for my question today using google and StackOverflow search engines... but no luck :)
I was wondering what are the key features of every framework for end user, and how can you characterize every framework from the end-user point of view (I've looked into Framework Design Guidelines by K. Cwalina, but I've found only concepts and guidelines for framework architects), for me:
it should be extensible
should let build extensible and reusable components
and of course : Simple things should be simple, complex things should be possible. (http://en.wikiquote.org/wiki/Alan_Kay)
I think there is much more out there.
Please share your knowledge.
Here are two good quotes from Ralph Johnson and Brian Foote
A framework is a reusable, ``semi-complete'' application that can be specialized to produce custom applications
One important characteristic of a framework is that the methods defined by the user to tailor the framework will often be called from within the framework itself, rather than from the user's application code. The framework often plays the role of the main program in coordinating and sequencing application activity. This inversion of control gives frameworks the power to serve as extensible skeletons. The methods supplied by the user tailor the generic algorithms defined in the framework for a particular application.
There was a special issue of CACM that you might want to take a look at too.
Here's one more link The Hollywood Principal. "Don't call us, we'll call you." About how the framework inverts the typical control so the framework calls your code instead of you calling some library code.
It sounds like you just want to know what is the defining characteristic of a framework...?
From FOLDOC:
In object-oriented systems, a set of classes that embodies an abstract design for solutions to a number of related problems.
So basically, a class library ("set of classes") that's extensible ("embodies an abstract design"),
I'll attempt a definition based on my own understanding: A framework is a body of code that abstracts a subset of tasks common to some classes of application programs. The intent is to provide, once, proven and tested code so that application programming doesn't have to keep re-inventing code for the common tasks handled by the framework.
In real life, frameworks often spring into being when a programmer or team get carried away with generalizing and future-proofing what started out as a single application. There's an honorable intent to start code re-use, but it often turns out that such frameworks aren't designed with intent from the beginning, don't have consistent design reflecting this intent, and are actually lousy code that ends up not being re-used at all. Most architects who feel qualified to create frameworks, aren't.
The difference between libraries and frameworks: You call libraries. Frameworks call you.
Answering your question covering the depth it deserves is beyond the scope of this forum. All you should do is read this book though its focused on .Net frmaework specifically and written by the designers of the .Net framework, I'm sure the wisdom and information that this book provides would be sufficient to answer your question and satisfy your curiosities on the subject.
Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries (2nd Edition)
alt text http://www.lybrary.com/images/0321605012.jpg
A Framework is for me a other name for a Library (like Boost and many others) that is not about only one Topic (there are Librarys about Math, Networking, whatever out there, but these are no Frameworks) and it is of course Extensible and you can combine the Features of it to do your Job.
I'm in some sort of confusion: at one hand Microsoft architects and surrounding web community promote MVVM pattern for building WPF apps, but from the other hand in Prism patterns and practices they uses absolutely other design patterns - MVP, Presentation Model and Supervising Controller! And not a single example of use pure MVVM! They even say nothing about using MVVM in their PRISM documentation! So, what should one do in this situation? Is it possible to use MVVM pattern in PRISM applications with the same level of freedom as with patterns listed above? I mean would it be more complex or not because of (probably) kind a native architectural optimization for these patterns?
Absolutely. PRISM glues the parts of your composite application together, but those parts may use MVVM or whatever pattern you prefer (as can your Shell).
You can definitely use MVVM with Prism.
Blaine Wastell from the Patterns and Practices group has said that the next version of Prism (v4) will contain more help for the MVVM pattern. I've read somewhere else that this means better support for MVVM in Blend, and more MVVM in the documentation.
http://blogs.msdn.com/blaine/archive/2010/01/15/prism-4-0.aspx