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  • python equivalent of filter() getting two output lists

    - by FX
    Let's say I have a list, and a filtering function. Using something like >>> filter(lambda x: x > 10, [1,4,12,7,42]) [12, 42] I can get the elements matching the criterion. Is there a function I could use that would output two lists, one of elements matching, one of the remaining elements? I could call the filter() function twice, but that's kinda ugly :) Edit: the order of elements should be conserved, and I may have identical elements multiple times.

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  • python-wordmatching

    - by challarao
    Write two functions, called countSubStringMatch and countSubStringMatchRecursive that take two arguments, a key string and a target string. These functions iteratively and recursively count the number of instances of the key in the target string. You should complete definitions for def countSubStringMatch(target,key): and def countSubStringMatchRecursive (target, key): For the remaining problems, we are going to explore other substring matching ideas. These problems can be solved with either an iterative function or a recursive one. You are welcome to use either approach, though you may find iterative approaches more intuitive in these cases of matching linear structures.

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  • My php script only reads the first row from mysql and doesn't check the rest of the rows for matches

    - by RobertH
    I'm trying to write a script for users to register to a club, and it does all the validation stuff properly and works great until it gets to the part where its supposed to check for duplicates. I'm not sure what is going wrong. HELP PLEASE!!! Thank you in Advance, <?php mysql_connect ("sqlhost", "username", "password") or die(mysql_error()); mysql_select_db ("databasename") or die(mysql_error()); $errormsgdb = ""; $errordb = "Sorry but that "; $error1db = "Name"; $error2db = "email"; $error3db = "mobile number"; $errordbe = " is already registered"; $pass1db = "No Matching Name"; $pass2db = "No Matching Email"; $pass3db = "No Matching Mobile"; $errorcount = 0; $qResult = mysql_query ("SELECT * FROM table"); $nRows = mysql_num_rows($qResult); for ($i=1; $i< $nRows+1; $i++){ $result = mysql_query("SELECT id,fname,lname,dob,email,mobile,agree,code,joindate FROM table WHERE fname = '$ffname"); if ($result > 0) { $errorcount = $errorcount++; $passdb = 0; $errormsgdb = $error1db; echo "<div class=\"box red\">$errordb $errormsgdb } else { $pass = 1; $errormsgdb = $pass1db; echo "<div class=\"box green\">$errormsgdb</div><br />"; } //--------------- Check if DB checks returned errors ------------------------------------> if($errorcount <= 0){ $dobp = $_REQUEST['day'].'/'.$_REQUEST['month'].'/'.$_REQUEST['year']; $dob = $_REQUEST['year'].$_REQUEST['month'].$_REQUEST['day']; //header('Location: thankyou.php?ffname='.$ffname.'&flname='.$flname.'&dob='.$dob.'&femail='.$femail.'&fmobile='.$fmobile.'&agree='.$agree.'&code='.$code.'&dobp='.$dobp); echo "<div class='box green'>Form completed! Error Count = $errorcount</div>"; } else { echo "<div class='box red'>There was an Error! Error Count = $errorcount</div>"; } } ?>

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  • Adding Related Entities without using navigation properties

    - by Barisa Puter
    I have the following classes, set for testing: public class Company { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } public string Name { get; set; } } public class Employee { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } public string Name { get; set; } public int CompanyId { get; set; } public virtual Company Company { get; set; } } public class EFTestDbContext : DbContext { public DbSet<Employee> Employees { get; set; } public DbSet<Company> Companies { get; set; } } For the sake of testing, I wanted to insert one company and one employee for that company with single SaveChanges call, like this: Company company = new Company { Name = "Sample company" }; context.Companies.Add(company); // ** UNCOMMENTED FOR TEST 2 //Company company2 = new Company //{ // Name = "Some other company" //}; //context.Companies.Add(company2); Employee employee = new Employee { Name = "Hans", CompanyId = company.Id }; context.Employees.Add(employee); context.SaveChanges(); Even though I am not using navigational properties, but instead I've made relation over Id, this somehow mysteriously worked - employee was saved with proper foreign key to company which got updated from 0 to real value, which made me go ?!?! Some hidden C# feature? Then I've decided to add more code, which is commented in the snippet above, making it to be inserting of 2 x Company entity and 1 x Employee entity, and then I got exception: Unable to determine the principal end of the 'CodeLab.EFTest.Employee_Company' relationship. Multiple added entities may have the same primary key. Does this mean that in cases where foreign key is 0, and there is a single matching entity being inserted in same SaveChanges transaction, Entity Framework will assume that foreign key should be for that matching entity? In second test, when there are two entities matching the relation type, Entity Framework throws an exception as it is not able to figure out to which of the Companies Employee should be related to.

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  • how do I get the SDK version for an app running on the simulator programmatically?

    - by newbiez
    I am trying to get the version/build that is running on the simulator via code. Basically I am checking various features of my app using the simulator, and want to switch code paths on and off based on which SDK do I have set as current, instead than doing it by hand every time (my testing machine has different version of the SDK on it and I switch the current for testing purposes between 4.1 and 5.1). So the idea is that when the app launch on the simulator, I can read the build of the SDK and know trough matching (I have a function that does the matching and turn on and off the features) if I should run a specific code path or not. I know how to figure out if I am running on the sim or on a device, but cannot find references about how to get the version of the SDK via code, so I am basically stuck. Is there any function that I can call and that returns me the build or version of the currently installed iOS, while I am running the app on the simulator?

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  • Why does this Bash regex match return an Exit Status of "2"?

    - by PreservedMoose
    I'm writing a Bash script that needs to scan for the existence of non-ASCII characters in filenames. I'm using the POSIX bracket regex syntax to match the non-ASCII characters, but for some reason, when I test for the match in an if/then statement, the test always returns an Exit Status of 2, and never matches my test string. Here's the code in question: FILEREQ_SOURCEFILE="Filename–WithNonAScII-Charàcters-05sec_23.98.mov" REGEX_MATCH_NONASCII="[^[:ascii:]]" if [[ $FILEREQ_SOURCEFILE =~ $REGEX_MATCH_NONASCII ]]; then echo "Exit Status: $?" echo "Matched!" else echo "Exit Status: $?" echo "No Match" fi This code always returns: Exit Status: 2 No Match I've read and re-read the bash-hackers.org explanation of how regex matching works, as well as this previous question on SO regarding matching non-ASCII characters, but for the life of me, I can't get this to work. What am I missing here?

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  • Do abstractions have to reduce code readability?

    - by Martin Blore
    A good developer I work with told me recently about some difficulty he had in implementing a feature in some code we had inherited; he said the problem was that the code was difficult to follow. From that, I looked deeper into the product and realised how difficult it was to see the code path. It used so many interfaces and abstract layers, that trying to understand where things began and ended was quite difficult. It got me thinking about the times I had looked at past projects (before I was so aware of clean code principles) and found it extremely difficult to get around in the project, mainly because my code navigation tools would always land me at an interface. It would take a lot of extra effort to find the concrete implementation or where something was wired up in some plugin type architecture. I know some developers strictly turn down dependency injection containers for this very reason. It confuses the path of the software so much that the difficulty of code navigation is exponentially increased. My question is: when a framework or pattern introduces so much overhead like this, is it worth it? Is it a symptom of a poorly implemented pattern? I guess a developer should look to the bigger picture of what that abstractions brings to the project to help them get through the frustration. Usually though, it's difficult to make them see that big picture. I know I've failed to sell the needs of IOC and DI with TDD. For those developers, use of those tools just cramps code readability far too much.

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  • ASP.NET MVC Framework

    - by Aamir Hasan
     MVC is a design pattern. A reusable "recipe" for constructing your application. Generally, you don't want your user interface code and data access code to be mixed together, it makes changing either one more difficult. By placing data access code into a "Model" object and user interface code into a "View" object, you can use a "Controller" object to act as a go-between, sending messages/calling methods on the view object when the data changes and vice versa. Model-view-controller (MVC) is an architectural pattern used in software engineering. In complex computer applications that present a large amount of data to the user, a developer often wishes to separate data (model) and user interface (view) concerns, so that changes to the user interface will not affect data handling, and that the data can be reorganized without changing the user interface. The model-view-controller solves this problem by decoupling data access and business logic from data presentation and user interaction, by introducing an intermediate component: the controller.Model:    The domain-specific representation of the information that the application operates. Domain logic adds meaning to raw data (e.g., calculating whether today is the user's birthday, or the totals, taxes, and shipping charges for shopping cart items).    Many applications use a persistent storage mechanism (such as a database) to store data. MVC does not specifically mention the data access layer because it is understood to be underneath or encapsulated by the Model.View:    Renders the model into a form suitable for interaction, typically a user interface element. Multiple views can exist for a single model for different purposes.Controller:    Processes and responds to events, typically user actions, and may invoke changes on the model.    

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  • Getting Query Parameters in Javascript

    - by PhubarBaz
    I find myself needing to get query parameters that are passed into a web app on the URL quite often. At first I wrote a function that creates an associative array (aka object) with all of the parameters as keys and returns it. But then I was looking at the revealing module pattern, a nice javascript design pattern designed to hide private functions, and came up with a way to do this without even calling a function. What I came up with was this nice little object that automatically initializes itself into the same associative array that the function call did previously. // Creates associative array (object) of query params var QueryParameters = (function() {     var result = {};     if (window.location.search)     {         // split up the query string and store in an associative array         var params = window.location.search.slice(1).split("&");         for (var i = 0; i < params.length; i++)         {             var tmp = params[i].split("=");             result[tmp[0]] = unescape(tmp[1]);         }     }     return result; }()); Now all you have to do to get the query parameters is just reference them from the QueryParameters object. There is no need to create a new object or call any function to initialize it. var debug = (QueryParameters.debug === "true"); or if (QueryParameters["debug"]) doSomeDebugging(); or loop through all of the parameters. for (var param in QueryParameters) var value = QueryParameters[param]; Hope you find this object useful.

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  • What design patters are the worst or most narrowly defined?

    - by Akku
    For every programming project, Managers with past programming experience try to shine when they recommend some design patterns for your project. I like design patterns when they make sense or if you need a scalbale solution. I've used Proxies, Observers and Command patterns in a positive way for example, and do so every day. But I'm really hesitant to use say a Factory pattern if there's only one way to create an object, as a factory might make it all easier in the future, but complicates the code and is pure overhead. So, my question is in respect to my future career and my answer to manager types throwing random pattern-names around: Which design patterns did you use, that threw you back overall? Which are the worst design patterns, that you shouldn't have a look at if it's not that only single situation where it makes sense (read: which design patterns are very narrowly defined)? (It's like I was looking for the negative reviews of an overall good product of amazon to see what bugged people most in using design patterns). And I'm not talking about Anti-Patterns here, but about Patterns that are usually thought of as "good" patterns.

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  • DEEP DIVE MVVM at #MIX11

    - by Laurent Bugnion
    The public (you!) has spoken, and “Deep Dive MVVM” was selected (along with 11 other open call talks) out of 217 proposals. There were 17’000 votes! These are pretty amazing numbers, and believe me when I tell you that I still didn’t completely realize what just happened! I want to really underline the outstanding quality of many of the talks that were proposed. I decided not to reveal my votes, because I just know too many of the candidates and I had only 10 votes but let’s just say that some of my favorites were picked, and some were not, and I really wish that I can see them all either at MIX or in another conference. I already started putting down ideas for the talk (not too many, because I didn’t want to jinx it) and it should be a really great session. We will, as the title shows, dive deep into the subtleties of MVVM, and explore some techniques that allow to overcome some of the hurdles presented by this pattern. This session will be shaped by many emails that I received over the past year, since “Understanding the MVVM pattern” was presented, and offered, for many, a first look into Model-View-ViewModel. So now’s the chance, comment and let me know what topics you would like to discuss. If you had not done so before, go ahead and watch last year’s session, it will be a great preparation. Let’s talk real life development, let’s explore the problems and find solutions. I already have a nice collection of emails asking questions around MVVM and my goal is to answer as many as I can. Leave a comment and I will do my best to answer these as well. The date/time was not announced yet, so watch this space for details. I am really looking forward to seeing many of you in Las Vegas, and for those who cannot make it, don’t worry, all the sessions will be published in video by the amazing MIX team a few hours after the session actually takes place. Thanks for your confidence and in the meantime, Happy Coding! Laurent Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Implement Budget Allocation in DAX for Power Pivot and Tabular #powerpivot #tabular #ssas #dax

    - by Marco Russo (SQLBI)
    Comparing sales and budget, or costs and budget, is a very common operation. However, it is often the case that you have different granularities for different tables containing budget and the data to compare with. There are two ways to do that: you can limit the comparison to the granularity that is common to the two tables, or you can allocate the budget where it’s not defined. For example, if you have a budget defined by quarter and category, you might want to allocate it by month and product. In this way, you will do the comparison as you had a more granular definition of the budget, without actually having to do the manual job of allocating data (usually in an Excel worksheet!). If you want to do budget allocation in DAX, you can use the Budget Patterns we published on DAX Patterns. If you come from and MDX/OLAP background, at first you might find it hard to solve the problem of not having attribute hierarchies that helps you in propagating the budget values to lower hierarchical levels. However, I think that once you get used to DAX, you will find the behavior very predictable and easy to “debug” also for more complex allocation formula. You just have to be careful in writing the DAX formula, but probably the pattern we wrote should help you designing the right data model, without creating physical relationships to the budget table! This pattern is also based on the Handling Different Granularities scenario I discussed a couple of weeks ago.

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  • Book Review: Getting Started With Window 8 Apps By Ben Dewey

    - by Tim Murphy
    When O’Reilly gave me an opportunity to review this book I was excited.  It gave me a reason to finally put some time into this new platform and what developers will need to learn in order to be successful. This book by Ben Dewey is only 92 pages long, so if you were looking for an in-depth treatment of Windows 8 development you will need supplemental materials.  It is also due for an update from the perspective of recent changes made by Microsoft prior to the final release of the OS and tools.  This causes a few issues if you try to run the code samples because of namespace changes. I was encouraged by the fact that the author didn’t do the typical “hello world” app.  He uses a lot of pattern based development techniques and hits many of the main topics including: Application lifecycle Charms integration Tiles Sensors The lifecycle is critical for anyone who hasn’t done mobile development before.  Limited resources on these devices mean that the OS can suspend or kill your app altogether if it decides it needs to.  He covers tombstoning which is the key to Windows 8 and Windows Phone lifecycle management. He also dedicates a chapter to marketing and distributing the application you build.  From my experience with Windows Phone development this is crucial information.  You need to know how to test your application so that it is going to pass certification and present your app so that it is going to get noticed amongst thousands of other apps. The main things that I wish had been in the book explanations of more of the common controls and more complete explanation of patterns that were implemented. In the end this book is a good foundation getting exposure to the concepts that underlie this new version of the Windows platform and how it effects developers.  It isn’t a book that I would suggest for someone just getting into development with no understanding of pattern based development. del.icio.us Tags: Windows 8,O'Reilly,Ben Dewey,Book Review,Review

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  • Dissecting ASP.NET Routing

    The ASP.NET Routing framework allows developers to decouple the URL of a resource from the physical file on the web server. Specifically, the developer defines routing rules, which map URL patterns to a class or ASP.NET page that generates the content. For instance, you could create a URL pattern of the form Categories/CategoryName and map it to the ASP.NET page ShowCategoryDetails.aspx; the ShowCategoryDetails.aspx page would display details about the category CategoryName. With such a mapping, users could view category about the Beverages category by visiting www.yoursite.com/Categories/Beverages. In short, ASP.NET Routing allows for readable, SEO-friendly URLs. ASP.NET Routing was first introduced in ASP.NET 3.5 SP1 and was enhanced further in ASP.NET 4.0. ASP.NET Routing is a key component of ASP.NET MVC, but can also be used with Web Forms. Two previous articles here on 4Guys showed how to get started using ASP.NET Routing: Using ASP.NET Routing Without ASP.NET MVC and URL Routing in ASP.NET 4.0. This article aims to explore ASP.NET Routing in greater depth. We'll explore how ASP.NET Routing works underneath the covers to decode a URL pattern and hand it off the the appropriate class or ASP.NET page. Read on to learn more! Read More >

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  • Dissecting ASP.NET Routing

    The ASP.NET Routing framework allows developers to decouple the URL of a resource from the physical file on the web server. Specifically, the developer defines routing rules, which map URL patterns to a class or ASP.NET page that generates the content. For instance, you could create a URL pattern of the form Categories/CategoryName and map it to the ASP.NET page ShowCategoryDetails.aspx; the ShowCategoryDetails.aspx page would display details about the category CategoryName. With such a mapping, users could view category about the Beverages category by visiting www.yoursite.com/Categories/Beverages. In short, ASP.NET Routing allows for readable, SEO-friendly URLs. ASP.NET Routing was first introduced in ASP.NET 3.5 SP1 and was enhanced further in ASP.NET 4.0. ASP.NET Routing is a key component of ASP.NET MVC, but can also be used with Web Forms. Two previous articles here on 4Guys showed how to get started using ASP.NET Routing: Using ASP.NET Routing Without ASP.NET MVC and URL Routing in ASP.NET 4.0. This article aims to explore ASP.NET Routing in greater depth. We'll explore how ASP.NET Routing works underneath the covers to decode a URL pattern and hand it off the the appropriate class or ASP.NET page. Read on to learn more! Read More >Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • C#: Why Decorate When You Can Intercept

    - by James Michael Hare
    We've all heard of the old Decorator Design Pattern (here) or used it at one time or another either directly or indirectly.  A decorator is a class that wraps a given abstract class or interface and presents the same (or a superset) public interface but "decorated" with additional functionality.   As a really simplistic example, consider the System.IO.BufferedStream, it itself is a descendent of System.IO.Stream and wraps the given stream with buffering logic while still presenting System.IO.Stream's public interface:   1: Stream buffStream = new BufferedStream(rawStream); Now, let's take a look at a custom-code example.  Let's say that we have a class in our data access layer that retrieves a list of products from a database:  1: // a class that handles our CRUD operations for products 2: public class ProductDao 3: { 4: ... 5:  6: // a method that would retrieve all available products 7: public IEnumerable<Product> GetAvailableProducts() 8: { 9: var results = new List<Product>(); 10:  11: // must create the connection 12: using (var con = _factory.CreateConnection()) 13: { 14: con.ConnectionString = _productsConnectionString; 15: con.Open(); 16:  17: // create the command 18: using (var cmd = _factory.CreateCommand()) 19: { 20: cmd.Connection = con; 21: cmd.CommandText = _getAllProductsStoredProc; 22: cmd.CommandType = CommandType.StoredProcedure; 23:  24: // get a reader and pass back all results 25: using (var reader = cmd.ExecuteReader()) 26: { 27: while(reader.Read()) 28: { 29: results.Add(new Product 30: { 31: Name = reader["product_name"].ToString(), 32: ... 33: }); 34: } 35: } 36: } 37: }            38:  39: return results; 40: } 41: } Yes, you could use EF or any myriad other choices for this sort of thing, but the germaine point is that you have some operation that takes a non-trivial amount of time.  What if, during the production day I notice that my application is performing slowly and I want to see how much of that slowness is in the query versus my code.  Well, I could easily wrap the logic block in a System.Diagnostics.Stopwatch and log the results to log4net or other logging flavor of choice: 1:     // a class that handles our CRUD operations for products 2:     public class ProductDao 3:     { 4:         private static readonly ILog _log = LogManager.GetLogger(typeof(ProductDao)); 5:         ... 6:         7:         // a method that would retrieve all available products 8:         public IEnumerable<Product> GetAvailableProducts() 9:         { 10:             var results = new List<Product>(); 11:             var timer = Stopwatch.StartNew(); 12:             13:             // must create the connection 14:             using (var con = _factory.CreateConnection()) 15:             { 16:                 con.ConnectionString = _productsConnectionString; 17:                 18:                 // and all that other DB code... 19:                 ... 20:             } 21:             22:             timer.Stop(); 23:             24:             if (timer.ElapsedMilliseconds > 5000) 25:             { 26:                 _log.WarnFormat("Long query in GetAvailableProducts() took {0} ms", 27:                     timer.ElapsedMillseconds); 28:             } 29:             30:             return results; 31:         } 32:     } In my eye, this is very ugly.  It violates Single Responsibility Principle (SRP), which says that a class should only ever have one responsibility, where responsibility is often defined as a reason to change.  This class (and in particular this method) has two reasons to change: If the method of retrieving products changes. If the method of logging changes. Well, we could “simplify” this using the Decorator Design Pattern (here).  If we followed the pattern to the letter, we'd need to create a base decorator that implements the DAOs public interface and forwards to the wrapped instance.  So let's assume we break out the ProductDAO interface into IProductDAO using your refactoring tool of choice (Resharper is great for this). Now, ProductDao will implement IProductDao and get rid of all logging logic: 1:     public class ProductDao : IProductDao 2:     { 3:         // this reverts back to original version except for the interface added 4:     } 5:  And we create the base Decorator that also implements the interface and forwards all calls: 1:     public class ProductDaoDecorator : IProductDao 2:     { 3:         private readonly IProductDao _wrappedDao; 4:         5:         // constructor takes the dao to wrap 6:         public ProductDaoDecorator(IProductDao wrappedDao) 7:         { 8:             _wrappedDao = wrappedDao; 9:         } 10:         11:         ... 12:         13:         // and then all methods just forward their calls 14:         public IEnumerable<Product> GetAvailableProducts() 15:         { 16:             return _wrappedDao.GetAvailableProducts(); 17:         } 18:     } This defines our base decorator, then we can create decorators that add items of interest, and for any methods we don't decorate, we'll get the default behavior which just forwards the call to the wrapper in the base decorator: 1:     public class TimedThresholdProductDaoDecorator : ProductDaoDecorator 2:     { 3:         private static readonly ILog _log = LogManager.GetLogger(typeof(TimedThresholdProductDaoDecorator)); 4:         5:         public TimedThresholdProductDaoDecorator(IProductDao wrappedDao) : 6:             base(wrappedDao) 7:         { 8:         } 9:         10:         ... 11:         12:         public IEnumerable<Product> GetAvailableProducts() 13:         { 14:             var timer = Stopwatch.StartNew(); 15:             16:             var results = _wrapped.GetAvailableProducts(); 17:             18:             timer.Stop(); 19:             20:             if (timer.ElapsedMilliseconds > 5000) 21:             { 22:                 _log.WarnFormat("Long query in GetAvailableProducts() took {0} ms", 23:                     timer.ElapsedMillseconds); 24:             } 25:             26:             return results; 27:         } 28:     } Well, it's a bit better.  Now the logging is in its own class, and the database logic is in its own class.  But we've essentially multiplied the number of classes.  We now have 3 classes and one interface!  Now if you want to do that same logging decorating on all your DAOs, imagine the code bloat!  Sure, you can simplify and avoid creating the base decorator, or chuck it all and just inherit directly.  But regardless all of these have the problem of tying the logging logic into the code itself. Enter the Interceptors.  Things like this to me are a perfect example of when it's good to write an Interceptor using your class library of choice.  Sure, you could design your own perfectly generic decorator with delegates and all that, but personally I'm a big fan of Castle's Dynamic Proxy (here) which is actually used by many projects including Moq. What DynamicProxy allows you to do is intercept calls into any object by wrapping it with a proxy on the fly that intercepts the method and allows you to add functionality.  Essentially, the code would now look like this using DynamicProxy: 1: // Note: I like hiding DynamicProxy behind the scenes so users 2: // don't have to explicitly add reference to Castle's libraries. 3: public static class TimeThresholdInterceptor 4: { 5: // Our logging handle 6: private static readonly ILog _log = LogManager.GetLogger(typeof(TimeThresholdInterceptor)); 7:  8: // Handle to Castle's proxy generator 9: private static readonly ProxyGenerator _generator = new ProxyGenerator(); 10:  11: // generic form for those who prefer it 12: public static object Create<TInterface>(object target, TimeSpan threshold) 13: { 14: return Create(typeof(TInterface), target, threshold); 15: } 16:  17: // Form that uses type instead 18: public static object Create(Type interfaceType, object target, TimeSpan threshold) 19: { 20: return _generator.CreateInterfaceProxyWithTarget(interfaceType, target, 21: new TimedThreshold(threshold, level)); 22: } 23:  24: // The interceptor that is created to intercept the interface calls. 25: // Hidden as a private inner class so not exposing Castle libraries. 26: private class TimedThreshold : IInterceptor 27: { 28: // The threshold as a positive timespan that triggers a log message. 29: private readonly TimeSpan _threshold; 30:  31: // interceptor constructor 32: public TimedThreshold(TimeSpan threshold) 33: { 34: _threshold = threshold; 35: } 36:  37: // Intercept functor for each method invokation 38: public void Intercept(IInvocation invocation) 39: { 40: // time the method invocation 41: var timer = Stopwatch.StartNew(); 42:  43: // the Castle magic that tells the method to go ahead 44: invocation.Proceed(); 45:  46: timer.Stop(); 47:  48: // check if threshold is exceeded 49: if (timer.Elapsed > _threshold) 50: { 51: _log.WarnFormat("Long execution in {0} took {1} ms", 52: invocation.Method.Name, 53: timer.ElapsedMillseconds); 54: } 55: } 56: } 57: } Yes, it's a bit longer, but notice that: This class ONLY deals with logging long method calls, no DAO interface leftovers. This class can be used to time ANY class that has an interface or virtual methods. Personally, I like to wrap and hide the usage of DynamicProxy and IInterceptor so that anyone who uses this class doesn't need to know to add a Castle library reference.  As far as they are concerned, they're using my interceptor.  If I change to a new library if a better one comes along, they're insulated. Now, all we have to do to use this is to tell it to wrap our ProductDao and it does the rest: 1: // wraps a new ProductDao with a timing interceptor with a threshold of 5 seconds 2: IProductDao dao = TimeThresholdInterceptor.Create<IProductDao>(new ProductDao(), 5000); Automatic decoration of all methods!  You can even refine the proxy so that it only intercepts certain methods. This is ideal for so many things.  These are just some of the interceptors we've dreamed up and use: Log parameters and returns of methods to XML for auditing. Block invocations to methods and return default value (stubbing). Throw exception if certain methods are called (good for blocking access to deprecated methods). Log entrance and exit of a method and the duration. Log a message if a method takes more than a given time threshold to execute. Whether you use DynamicProxy or some other technology, I hope you see the benefits this adds.  Does it completely eliminate all need for the Decorator pattern?  No, there may still be cases where you want to decorate a particular class with functionality that doesn't apply to the world at large. But for all those cases where you are using Decorator to add functionality that's truly generic.  I strongly suggest you give this a try!

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  • SQLAuthority News – 2 Whitepapers Announced – AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution

    - by pinaldave
    Understanding AlwaysOn Architecture is extremely important when building a solution with failover clusters and availability groups. Microsoft has just released two very important white papers related to this subject. Both the white papers are written by top experts in industry and have been reviewed by excellent panel of experts. Every time I talk with various organizations who are adopting the SQL Server 2012 they are always excited with the concept of the new feature AlwaysOn. One of the requests I often here is the related to detailed documentations which can help enterprises to build a robust high availability and disaster recovery solution. I believe following two white paper now satisfies the request. AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution by Using AlwaysOn Availability Groups SQL Server 2012 AlwaysOn Availability Groups provides a unified high availability and disaster recovery (HADR) solution. This paper details the key topology requirements of this specific design pattern on important concepts like quorum configuration considerations, steps required to build the environment, and a workflow that shows how to handle a disaster recovery. AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution by Using Failover Cluster Instances and Availability Groups SQL Server 2012 AlwaysOn Failover Cluster Instances (FCI) and AlwaysOn Availability Groups provide a comprehensive high availability and disaster recovery solution. This paper details the key topology requirements of this specific design pattern on important concepts like asymmetric storage considerations, quorum model selection, quorum votes, steps required to build the environment, and a workflow. If you are not going to implement AlwaysOn feature, this two Whitepapers are still a great reference material to review as it will give you complete idea regarding what it takes to implement AlwaysOn architecture and what kind of efforts needed. One should at least bookmark above two white papers for future reference. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, T SQL, Technology Tagged: AlwaysOn

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  • What, if anything, to do about bow-shaped burndowns?

    - by Karl Bielefeldt
    I've started to notice a recurring pattern to our team's burndown charts, which I call a "bowstring" pattern. The ideal line is the "string" and the actual line starts out relatively flat, then curves down to meet the target like a bow. My theory on why they look like this is that toward the beginning of the story, we are doing a lot of debugging or exploratory work that is difficult to estimate remaining work for. Sometimes it even goes up a little as we discover a task is more difficult once we get into it. Then we get into implementation and test which is more predictable, hence the curving down graph. Note I'm not talking about a big scale like BDUF, just the natural short-term constraint that you have to find the bug before you can fix it, coupled with the fact that stories are most likely to start toward the beginning of a two-week iteration. Is this a common occurrence among scrum teams? Do people see it as a problem? If so, what is the root cause and some techniques to deal with it?

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  • Evil DRY

    - by StefanSteinegger
    DRY (Don't Repeat Yourself) is a basic software design and coding principle. But there is just no silver bullet. While DRY should increase maintainability by avoiding common design mistakes, it could lead to huge maintenance problems when misunderstood. The root of the problem is most probably that many developers believe that DRY means that any piece of code that is written more then once should be made reusable. But the principle is stated as "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system." So the important thing here is "knowledge". Nobody ever said "every piece of code". I try to give some examples of misusing the DRY principle. Code Repetitions by Coincidence There is code that is repeated by pure coincidence. It is not the same code because it is based on the same piece of knowledge, it is just the same by coincidence. It's hard to give an example of such a case. Just think about some lines of code the developer thinks "I already wrote something similar". Then he takes the original code, puts it into a public method, even worse into a base class where none had been there before, puts some weird arguments and some if or switch statements into it to support all special cases and calls this "increasing maintainability based on the DRY principle". The resulting "reusable method" is usually something the developer not even can give a meaningful name, because its contents isn't anything specific, it is just a bunch of code. For the same reason, nobody will really understand this piece of code. Typically this method only makes sense to call after some other method had been called. All the symptoms of really bad design is evident. Fact is, writing this kind of "reusable methods" is worse then copy pasting! Believe me. What will happen when you change this weird piece of code? You can't say what'll happen, because you can't understand what the code is actually doing. So better don't touch it anymore. Maintainability just died. Of course this problem is with any badly designed code. But because the developer tried to make this method as reusable as possible, large parts of the system get dependent on it. Completely independent parts get tightly coupled by this common piece of code. Changing on the single common place will have effects anywhere in the system, a typical symptom of too tight coupling. Without trying to dogmatically (and wrongly) apply the DRY principle, you just had a system with a weak design. Now you get a system which just can't be maintained anymore. So what can you do against it? When making code reusable, always identify the generally reusable parts of it. Find the reason why the code is repeated, find the common "piece of knowledge". If you have to search too far, it's probably not really there. Explain it to a colleague, if you can't explain or the explanation is to complicated, it's probably not worth to reuse. If you identify the piece of knowledge, don't forget to carefully find the place where it should be implemented. Reusing code is never worth giving up a clean design. Methods always need to do something specific. If you can't give it a simple and explanatory name, you did probably something weird. If you can't find the common piece of knowledge, try to make the code simpler. For instance, if you have some complicated string or collection operations within this code, write some general-purpose operations into a helper class. If your code gets simple enough, its not so bad if it can't be reused. If you are not able to find anything simple and reasonable, copy paste it. Put a comment into the code to reference the other copies. You may find a solution later. Requirements Repetitions by Coincidence Let's assume that you need to implement complex tax calculations for many countries. It's possible that some countries have very similar tax rules. These rules are still completely independent from each other, since every country can change it of its own. (Assumed that this similarity is actually by coincidence and not by political membership. There might be basic rules applying to all European countries. etc.) Let's assume that there are similarities between an Asian country and an African country. Moving the common part to a central place will cause problems. What happens if one of the countries changes its rules? Or - more likely - what happens if users of one country complain about an error in the calculation? If there is shared code, it is very risky to change it, even for a bugfix. It is hard to find requirements to be repeated by coincidence. Then there is not much you can do against the repetition of the code. What you really should consider is to make coding of the rules as simple as possible. So this independent knowledge "Tax Rules in Timbuktu" or wherever should be as pure as possible, without much overhead and stuff that does not belong to it. So you can write every independent requirement short and clean. DRYing try-catch and using Blocks This is a technical issue. Blocks like try-catch or using (e.g. in C#) are very hard to DRY. Imagine a complex exception handling, including several catch blocks. When the contents of the try block as well as the contents of the individual catch block are trivial, but the whole structure is repeated on many places in the code, there is almost no reasonable way to DRY it. try { // trivial code here using (Thingy thing = new thingy) { //trivial, but always different line of code } } catch(FooException foo) { // trivial foo handling } catch (BarException bar) { // trivial bar handling } catch { // trivial common handling } finally { // trivial finally block } The key here is that every block is trivial, so there is nothing to just move into a separate method. The only part that differs from case to case is the line of code in the body of the using block (or any other block). The situation is especially interesting if the many occurrences of this structure are completely independent: they appear in classes with no common base class, they don't aggregate each other and so on. Let's assume that this is a common pattern in service methods within the whole system. Examples of Evil DRYing in this situation: Put a if or switch statement into the method to choose the line of code to execute. There are several reasons why this is not a good idea: The close coupling of the formerly independent implementation is the strongest. Also the readability of the code and the use of a parameter to control the logic. Put everything into a method which takes a delegate as argument to call. The caller just passes his "specific line of code" to this method. The code will be very unreadable. The same maintainability problems apply as for any "Code Repetition by Coincidence" situations. Enforce a base class to all the classes where this pattern appears and use the template method pattern. It's the same readability and maintainability problem as above, but additionally complex and tightly coupled because of the base class. I would call this "Inheritance by Coincidence" which will not lead to great software design. What can you do against it: Ideally, the individual line of code is a call to a class or interface, which could be made individual by inheritance. If this would be the case, it wouldn't be a problem at all. I assume that it is no such a trivial case. Consider to refactor the error concept to make error handling easier. The last but not worst option is to keep the replications. Some pattern of code must be maintained in consistency, there is nothing we can do against it. And no reason to make it unreadable. Conclusion The DRY-principle is an important and basic principle every software developer should master. The key is to identify the "pieces of knowledge". There is code which can't be reused easily because of technical reasons. This requires quite a bit flexibility and creativity to make code simple and maintainable. It's not the problem of the principle, it is the problem of blindly applying a principle without understanding the problem it should solve. The result is mostly much worse then ignoring the principle.

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  • SEO for Country & Language Specific content.

    - by kecebongsoft
    Currently I am creating a website which has a common topic for an article, but it's going to be different content for each country, and also, each of that content will be provided in several languages. And this mechanism exists in most of the parts in the website. For example, I have an article about tax. This article has to be different for each country, for example china. And tax content for china should be written in china AND english language (for non china-speaker). What is the best URL pattern to handle this? What I've been thinking is, using a sub folder (/country-code/language-code/) such as: www.example.com/cn/cn/tax www.example.com/cn/en/tax Or using top level domain such as: www.example.cn/cn/tax www.example.cn/en/tax Or subdomain such as cn.example.com/cn/tax cn.example.com/en/tax I think I will not prefer the last option since I might need to use subdomain for other purpose. Which left only subfolder and TLDN. I've read some articles saying that TLDN is good for localized content (language-specific content), but in my case, my TLDN will also has english contents (for non local speaker) which is specific only to that particular country (also the purpose of this is to let people from other country easily search it through google). What is the best pattern to pick and why?.

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  • How to implement early exit / return in Haskell?

    - by Giorgio
    I am porting a Java application to Haskell. The main method of the Java application follows the pattern: public static void main(String [] args) { if (args.length == 0) { System.out.println("Invalid number of arguments."); System.exit(1); } SomeDataType d = getData(arg[0]); if (!dataOk(d)) { System.out.println("Could not read input data."); System.exit(1); } SomeDataType r = processData(d); if (!resultOk(r)) { System.out.println("Processing failed."); System.exit(1); } ... } So I have different steps and after each step I can either exit with an error code, or continue to the following step. My attempt at porting this to Haskell goes as follows: main :: IO () main = do a <- getArgs if ((length args) == 0) then do putStrLn "Invalid number of arguments." exitWith (ExitFailure 1) else do -- The rest of the main function goes here. With this solution, I will have lots of nested if-then-else (one for each exit point of the original Java code). Is there a more elegant / idiomatic way of implementing this pattern in Haskell? In general, what is a Haskell idiomatic way to implement an early exit / return as used in an imperative language like Java?

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  • Trying to learn how to use WCF services in a WPF app, using MVVM

    - by Rod
    We're working on a major re-write of a legacy VB6 app, into a WPF app. I've written several WCF services, which are meant to be used with the new WPF app. We want to use the MVVM design pattern to do this, but we don't have experience at that. So, in order to learn MVVM we've watched a video on WindowsClient called How Do I: Build Data-driven WPF Application using the MVVM pattern. This is a great introduction, and we refer to it a lot, but for our situation it doesn't quite give us enough. For example, we're not certain how to use datasets returned by my WCF services in our new WPF app using the ideas that Todd Miranda introduced in the video I referenced. If we did as we think we're supposed to do, then we should design a class that is exactly like the class of data returned in my WCF service. But we're wondering, why do that, when the WCF service already has such a class? And yet, the class in the WPF app has to at least implement the INotifyPropertyChanged interface. So, we're not sure what to do.

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  • What design patterns are the worst or most narrowly defined?

    - by Akku
    For every programming project, Managers with past programming experience try to shine when they recommend some design patterns for your project. I like design patterns when they make sense or if you need a scalbale solution. I've used Proxies, Observers and Command patterns in a positive way for example, and do so every day. But I'm really hesitant to use say a Factory pattern if there's only one way to create an object, as a factory might make it all easier in the future, but complicates the code and is pure overhead. So, my question is in respect to my future career and my answer to manager types throwing random pattern-names around: Which design patterns did you use, that threw you back overall? Which are the worst design patterns, that you shouldn't have a look at if it's not that only single situation where it makes sense (read: which design patterns are very narrowly defined)? (It's like I was looking for the negative reviews of an overall good product of amazon to see what bugged people most in using design patterns). And I'm not talking about Anti-Patterns here, but about Patterns that are usually thought of as "good" patterns. Edit: As some answered, the problem is most often that patterns are not "bad" but "used wrong". If you know patterns, that are often misused or even difficult to use, they would also fit as an answer.

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  • How should I implement a command processing application?

    - by Nini Michaels
    I want to make a simple, proof-of-concept application (REPL) that takes a number and then processes commands on that number. Example: I start with 1. Then I write "add 2", it gives me 3. Then I write "multiply 7", it gives me 21. Then I want to know if it is prime, so I write "is prime" (on the current number - 21), it gives me false. "is odd" would give me true. And so on. Now, for a simple application with few commands, even a simple switch would do for processing the commands. But if I want extensibility, how would I need to implement the functionality? Do I use the command pattern? Do I build a simple parser/interpreter for the language? What if I want more complex commands, like "multiply 5 until >200" ? What would be an easy way to extend it (add new commands) without recompiling? Edit: to clarify a few things, my end goal would not be to make something similar to WolframAlpha, but rather a list (of numbers) processor. But I want to start slowly at first (on single numbers). I'm having in mind something similar to the way one would use Haskell to process lists, but a very simple version. I'm wondering if something like the command pattern (or equivalent) would suffice, or if I have to make a new mini-language and a parser for it to achieve my goals?

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