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• What makes MVVM uniquely suited to WPF?

  - by Reed Copsey

  The Model-View-ViewModel is very popular with WPF and Silverlight. I've been using this for my most recent projects, and am a very large fan. I understand that it's a refinement of MVP. However, I am wondering exactly what unique characteristics of WPF (and Silverlight) allow MVVM to work, and prevent (or at least make difficult) this pattern from working using other frameworks or technologies. I know MVVM has a strong dependency on the powerful data binding technology within WPF. This is the one feature which many articles and blogs seem to mention as being the key to WPF providing the means of the strong separation of View from ViewModel. However, data binding exists in many forms in other UI frameworks. There are even projects like Truss that provide WPF-style databinding to POCO in .NET. What features, other than data binding, make WPF and Silverlight uniquely suited to Model-View-ViewModel?

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• Does ActiveRecord make Ruby on Rails code hard to test?

  - by Erik Öjebo

  I've spent most of my time in statically typed languages (primarily C#). I have some bad experiences with the Active Record pattern and unit testing, because of the static methods and the mix of entities and data access code. Since the Ruby community probably is the most test driven of the communities out there, and the Rails ActiveRecord seems popular, there must be some way of combining TDD and ActiveRecord based code in Ruby on Rails. I would guess that the problem goes away in dynamic languages, somehow, but I don't see how. So, what's the trick?

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• MVC - Calling Controller Methods

  - by JT703

  Hello, My application is following the MVC design pattern. The problem I keep running into is needing to call methods inside a Controller class from outside that Controller class (ex. A View class wants to call a Controller method, or a Manager class wants to call a Controller method). Is calling Controller methods in this way allowed in MVC? If it's allowed, what's the proper way to do it? According to the version of MVC that I am following (there seems to be so many different versions out there), the View knows of the Model, and the Controller knows of the View. Doing it this way, I can't access the controller. Here's the best site I've found and the one describing the version of MVC I'm following: http://leepoint.net/notes-java/GUI/structure/40mvc.html. The Main Program code block really shows how this works. Thanks for any answers.

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• Advantages of Thread pooling in embedded systems

  - by Microkernel

  I am looking at the advantages of threadpooling design pattern in Embedded systems. I have listed few advantages, please go through them, comment and please suggest any other possible advantages that I am missing. Scalability in systems like ucos-2 where there is limit on number of threads. Increasing capability of any task when necessary like Garbage collection (say in normal systems if garbage collection is running under one task, its not possible to speed it up, but in threadpooling we can easily speed it up). Can set limit on the max system load. Please suggest if I am missing anything.

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• Linq-to-sql Compiled Query is returning result from different DataContext

  - by Vladimir Kojic

  Compiled query: public static Func<OperationalDataContext, short, Machine> QueryMachineById = CompiledQuery.Compile((OperationalDataContext db, short machineID) => db.Machines.Where(m => m.MachineID == machineID).SingleOrDefault()); It looks like compiled query is caching Machine object and returning the same object even if query is called from new DataContext (I’m disposing DataContext in the service but I’m getting Machine from previous DataContext). I use POCOs and XML mapping. Revised: It looks like compiled query is returning result from new data context and it is not using the one that I passed in compiled-query. Therefore I can not reuse returned object and link it to another object obtained from datacontext thru non compiled queries. I’m using unit of work pattern : // First Call Using(new DataContext) { Machine from DataContext.Table == machine from cached query } // Do some work // Second Call is failing Using(new DataContext) { Machine from DataContext.Table <> machine from cached query }

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• Algorithm on trajectory analysis.

  - by Arman

  Hello, I would like to analyse the trajectory data based on given templates. I need to stack the similar trajectories together. The data is a set of coordinates xy,xy,xy and the templates are again the lines defined by the set of control points. I don't know to what direction to go, maybe to Neural Networks or pattern recognition? Could you please advace me page, book or library to start with? kind regards Arman. PS. Is it the right place to ask the question?

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• Are SOLID principles really solid?

  - by Arseny

  The first pattern stands for this acronym is SRP. Here is a quote. the single responsibility principle states that every object should have a single responsibility, and that responsibility should be entirely encapsulated by the class. That's is simple and clear till we start to code ) Suppose we have a class with well defined SRP. To serialize this class instances we need to add special atrributes to that class. So now the class have other responsibility. Dosen't it violate SRP? Let's see other story. Interface implementation. Then we implement an interface we simply add other responsibility say dispose its resorces or compare its instances or whatever. So my question. Is it possible to keep SRP complete? How can we do it?

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• How do you mock a Sealed class?

  - by Brett Veenstra

  Mocking sealed classes can be quite a pain. I currently favor an Adapter pattern to handle this, but something about just keeps feels weird. So, What is the best way you mock sealed classes? Java answers are more than welcome. In fact, I would anticipate that the Java community has been dealing with this longer and has a great deal to offer. But here are some of the .NET opinions: Why Duck Typing Matters for C# Develoepers Creating wrappers for sealed and other types for mocking Unit tests for WCF (and Moq)

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• String replacement problem.

  - by fastcodejava

  I want to provide some template for a code generator I am developing. A typical pattern for class is : public ${class_type} ${class_name} extends ${super_class} implements ${interfaces} { ${class_body} } Problem is if super_class is blank or interfaces. I replace extends ${super_class} with empty string. But I get extra spaces. So a class with no super_class and interfaces end up like : public class Foo { //see the extra spaces before {? ${class_body} } I know I can replace multiple spaces with single, but is there any better approach?

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• Parsing an RFC822-Datetime in .NETMF 4.0

  - by chris12892

  I have an application written in .NETMF that requires that I be able to parse an RFC822-Datetime. Normally, this would be easy, but NETMF does not have a DateTime.parse() method, nor does it have some sort of a pattern matching implementation, so I'm pretty much stuck. Any ideas? EDIT: "Intelligent" solutions are probably needed. Part of the reason this is difficult is that the datetime in question has a tendency to have extra spaces in it (but only sometimes). A simple substring solution might work one day, but fail the next when the datetime has an extra space somewhere between the parts. I do not have control over the datetime, it is from the NOAA.

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• Passing sql results to views hard-codes views to database column names

  - by Galen

  I just realized that i may not be following best practices in regards to the MVC pattern. My issue is that my views "know" information about my database Here's my situation in psuedo code... My controller invokes a method from my model and passes it directly to the view view.records = tableGateway.getRecords() view.display() in my view each records as record print record.name print record.address ... In my view i have record.name and record.address, info that's hard-coded to my database. Is this bad? What other ways around it are there other than iterating over everything in the controller and basically rewriting the records collection. And that just seems silly. Thanks

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• Selective PHP autoload

  - by Extrakun

  I am writing a add-on module which is integrated with an existing PHP application; Because I am using a MVC pattern, and which may requires lot of inclusion of classes (which might not be used at all depending on the action of the user), I decide to use autoloading of classes. However, I have to ensure that the autoload function does not interferes with the normal operations of the existing applications. Does autoload only kicks in if a class name is not defined? Say I have to write another module which uses its own autoload functions (say, I have an autoload for a module, since they each reside in their own folder), how do I differentiate which module is it for? For #2, I thought of 2 options. Either prefix the class name with the module name (Such as 'MyNewModule_View_Default' and 'AnotherModule_View_Default'), or use file_exists to check the include file exists. Other suggestions are welcomed too!

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• Pyramid.security: Is getting user info from a database with unauthenticated_userid(request) really secure?

  - by yourfriendzak

  I'm trying to make an accesible cache of user data using Pyramid doc's "Making A “User Object” Available as a Request Attribute" example. They're using this code to return a user object to set_request_property: from pyramid.security import unauthenticated_userid def get_user(request): # the below line is just an example, use your own method of # accessing a database connection here (this could even be another # request property such as request.db, implemented using this same # pattern). dbconn = request.registry.settings['dbconn'] userid = unauthenticated_userid(request) if userid is not None: # this should return None if the user doesn't exist # in the database return dbconn['users'].query({'id':userid}) I don't understand why they're using unauthenticated_userid(request) to lookup user info from the database...isn't that insecure? That means that user might not be logged in, so why are you using that ID to get there private info from the database? Shouldn't userid = authenticated_userid(request) be used instead to make sure the user is logged in? What's the advantage of using unauthenticated_userid(request)? Please help me understand what's going on here.

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• ASP.NET MVC Data passing

  - by user295541

  Hi, I need a good example or guideline which could give me a pattern for data passing between view and partial view. For example I have a view which contains several partial views. I refresh these partial view by ajax. So I need to pass data among view and its partial views. The best way would be if I could pass data without using Temp data dictionary. Anybody know a good article about this? l.

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• Pulling and pushing between two google code repositories

  - by Kim L

  I'll start by quoting google's blog Project owners can now create multiple repositories for their project, and they can choose to make any of those new repositories a clone of any of the project's other repositories. These project clones share the same commit access permissions as the original project and make it easier for project members to work together on new features. A common pattern in the Mercurial world is to place each "official" branch into a separate repository with naming conventions like "project-crew", "project-stable", and so on. I've done exactly this. I have my default repository and then I've cloned that repository to a repo named "dev". I intend to use the default repository as my stable repo and then the dev repo as my primary development repo. Now I'm just wondering how on earth I should go about to pull and push between the default and the dev repositories?

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• Compiler optimization of repeated accessor calls

  - by apocalypse9

  I've found recently that for some types of financial calculations that the following pattern is much easier to follow and test especially in situations where we may need to get numbers from various stages of the computation. public class nonsensical_calculator { ... double _rate; int _term; int _days; double monthlyRate { get { return _rate / 12; }} public double days { get { return (1 - i); }} double ar { get { return (1+ days) /(monthlyRate * days) double bleh { get { return Math.Pow(ar - days, _term) public double raar { get { return bleh * ar/2 * ar / days; }} .... } Obviously this often results in multiple calls to the same accessor within a given formula. I was curious as to whether or not the compiler is smart enough to optimize away these repeated calls with no intervening change in state, or whether this style is causing a decent performance hit. Further reading suggestions are always appreciated

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• Postgresql - one database for everyone, or one-database per customer

  - by user337876

  I'm working on a web-based business application where each customer will need to have their own data (think basecamphq.com type model) For scalability and ease-of-upgrades, I'd prefer to have a single database where each customer gets a filtered version of the data. The problem is how to guarantee that they stay sandboxed to their own data. Trying to enforce it in code seems like a disaster waiting to happen. I know Oracle has a way to append a where clause to every query based on a login id, but does Postgresql have anything similar? If not, is there a different design pattern I could use (like creating a view of each table for each customer that filters)? Worse case scenario, what is the performance/memory overhead of having 1000 100M databases vs having a single 1Tb database? I will need to provide backup/restore functionality on a per-customer basis which is dead-simple on a single database but quite a bit trickier if they are sharing the database with other customers.

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• The right way to manage subviews in a UIControl

  - by ed94133

  (iPhone SDK 3.x:) I have a UIControl subclass that creates a different number of subviews depending on the length of an NSArray property. Please take my word for it that this needs to be a UIControl rather than a UIView. Currently I implement subview management in drawRect, beginning by removing all subviews and then creating the appropriate number based on the property. I don't think this is very good memory management and I'm not sure if drawRect is really the appropriate place to add subviews. Any thoughts on the best way to handle this pattern? Thank you.

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• Infopath - changing sql servers

  - by ScottStonehouse

  I have an InfoPath form which has sort of a master-detail pattern, with two tables in the underlying main datasource. I am trying to migrate this to a new SQL Server - same database, just moved from a SQL2005 machine to a SQL2008 machine. If I change the servername, it also wants me to change the database and tables. If I select the same database and master table, the bindings are maintains for the master table. But there doesn't appear to be a way to select multiple tables when you change the datasource, so you lose the detail bindings. Am I missing something - I'm pretty new to InfoPath.

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• sql server 2008 notifications

  - by Alexander Stalt

  C#, VS 2005, Sql Server 2008 I have a database on a remote server. It has a table table1. Several clients works with it. Every(each?) client can change content of table1. Every(each?) client must represent actual content of this table. So I need some algorythm (pattern) to keep clients represent actual content of table1. I know that sql server 2008 supports notification mechanism (reporting services). How can I use it for my task ?

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• I need to Split a string based on a complex delimiter

  - by Jason

  In C# I need to split a string (a log4j log file) into array elements based on a particular sequence of characters, namely "nnnn-nn-nn nn:nn:nn INFO". I'm currently splitting this log file up by newlines, which is fine except when the log statements themselves contain newlines. I don't control the input (the log file) so escaping them somehow is not an option. It seems like I should be able to use a comparator or a regex to identify the strings, but String.Split does not have an option like that. Am I stuck rolling my own, or is there a pattern or framework component that can be of help here?

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• How to handle BL cache for multiple web applications?

  - by Eran Betzalel

  I recently received a project that contains multiple web applications with no MVC structure. For starters I've created a library (DLL) that will contain the main Business Logic. The problem is with Caching - If I use the current web context cache object than I might end up with duplicate caching (as the web context will be different for every application). I'm currently thinking about implementing a simple caching mechanism with a singleton pattern that will allow the different web sites (aka different application domains) to share their "caching wisdom". I'd like to know what is the best way to solve this problem.

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• How do I write a custom validator for a zend form element with customized error messages?

  - by Mallika Iyer

  I have a question field with a list of allowed characters : A-Z,0-9,colon (:), question mark (?), comma(,), hyphen(-), apostrophe ('). I have the regex which works fine, in the fashion : $question->addValidator('regex', true, array(<regular expresstion>)) The default error message is something like ''' does not match against pattern '' I want to write a custom error message that says ' is not allowed in this field' Is there a simple way to do it using the existing zend components that I'm missing? Is writing a custom validator the only way to achieve what I'm trying to achieve? If yes, how do I write a custom validator (I looked at the documentation and didn't quite understand how I can customize the error messages) If there is any other way, I'd most appreciate that input too. Thanks for taking the time to answer this!

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• JUnit Best Practice: Different Fixtures for each @Test

  - by Juri Glass

  Hi I understand that there are @Before and @BeforeClass, which are used to define fixtures for the @Test's. But what should I use if I need different fixtures for each @Test? Should I define the fixture in the @Test? Should I create a test class for each @Test? I am asking for the best practices here, since both solutions aren't clean in my opinion. With the first solution, I would test the initialization code. And with the second solution I would break the "one test class for each class" pattern.

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• Building big, immutable objects without using constructors having long parameter lists

  - by Malax

  Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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