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• A Comparative Performance Analysis of Longene VS Wine

  <b>Longene.org:</b> Test methods:<br> 1. Get a computer with Linux installed.<br> 2. Install Wine and then test it with our test programs.

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• Squid parent cache for text/html only

  - by Salvador

  How do I configure the squid to only request text/html to the parent cache; right now I am using : cache_peer 127.0.0.1 parent 8080 0 no-query no-digest on the second hand I get a lot of direct request that do not use the parent proxy: some queries go like FIRST_UP_PARENT and some like DIRECT, how do I tell the squid to always use parent for text/html BTW .. is a transparent proxy I have tried : cache_peer 127.0.0.1 parent 8080 0 no-query no-digest acl elhtml req_mime_type -i ^text/html$ acl elhtml req_mime_type -i text/html cache_peer_access 127.0.0.1 allow elhtml cache_peer_access 127.0.0.1 deny all and it does not works Thanks in advance for the help.

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• How accurate is "Business logic should be in a service, not in a model"?

  - by Jeroen Vannevel

  Situation Earlier this evening I gave an answer to a question on StackOverflow. The question: Editing of an existing object should be done in repository layer or in service? For example if I have a User that has debt. I want to change his debt. Should I do it in UserRepository or in service for example BuyingService by getting an object, editing it and saving it ? My answer: You should leave the responsibility of mutating an object to that same object and use the repository to retrieve this object. Example situation: class User { private int debt; // debt in cents private string name; // getters public void makePayment(int cents){ debt -= cents; } } class UserRepository { public User GetUserByName(string name){ // Get appropriate user from database } } A comment I received: Business logic should really be in a service. Not in a model. What does the internet say? So, this got me searching since I've never really (consciously) used a service layer. I started reading up on the Service Layer pattern and the Unit Of Work pattern but so far I can't say I'm convinced a service layer has to be used. Take for example this article by Martin Fowler on the anti-pattern of an Anemic Domain Model: There are objects, many named after the nouns in the domain space, and these objects are connected with the rich relationships and structure that true domain models have. The catch comes when you look at the behavior, and you realize that there is hardly any behavior on these objects, making them little more than bags of getters and setters. Indeed often these models come with design rules that say that you are not to put any domain logic in the the domain objects. Instead there are a set of service objects which capture all the domain logic. These services live on top of the domain model and use the domain model for data. (...) The logic that should be in a domain object is domain logic - validations, calculations, business rules - whatever you like to call it. To me, this seemed exactly what the situation was about: I advocated the manipulation of an object's data by introducing methods inside that class that do just that. However I realize that this should be a given either way, and it probably has more to do with how these methods are invoked (using a repository). I also had the feeling that in that article (see below), a Service Layer is more considered as a façade that delegates work to the underlying model, than an actual work-intensive layer. Application Layer [his name for Service Layer]: Defines the jobs the software is supposed to do and directs the expressive domain objects to work out problems. The tasks this layer is responsible for are meaningful to the business or necessary for interaction with the application layers of other systems. This layer is kept thin. It does not contain business rules or knowledge, but only coordinates tasks and delegates work to collaborations of domain objects in the next layer down. It does not have state reflecting the business situation, but it can have state that reflects the progress of a task for the user or the program. Which is reinforced here: Service interfaces. Services expose a service interface to which all inbound messages are sent. You can think of a service interface as a façade that exposes the business logic implemented in the application (typically, logic in the business layer) to potential consumers. And here: The service layer should be devoid of any application or business logic and should focus primarily on a few concerns. It should wrap Business Layer calls, translate your Domain in a common language that your clients can understand, and handle the communication medium between server and requesting client. This is a serious contrast to other resources that talk about the Service Layer: The service layer should consist of classes with methods that are units of work with actions that belong in the same transaction. Or the second answer to a question I've already linked: At some point, your application will want some business logic. Also, you might want to validate the input to make sure that there isn't something evil or nonperforming being requested. This logic belongs in your service layer. "Solution"? Following the guidelines in this answer, I came up with the following approach that uses a Service Layer: class UserController : Controller { private UserService _userService; public UserController(UserService userService){ _userService = userService; } public ActionResult MakeHimPay(string username, int amount) { _userService.MakeHimPay(username, amount); return RedirectToAction("ShowUserOverview"); } public ActionResult ShowUserOverview() { return View(); } } class UserService { private IUserRepository _userRepository; public UserService(IUserRepository userRepository) { _userRepository = userRepository; } public void MakeHimPay(username, amount) { _userRepository.GetUserByName(username).makePayment(amount); } } class UserRepository { public User GetUserByName(string name){ // Get appropriate user from database } } class User { private int debt; // debt in cents private string name; // getters public void makePayment(int cents){ debt -= cents; } } Conclusion All together not much has changed here: code from the controller has moved to the service layer (which is a good thing, so there is an upside to this approach). However this doesn't look like it had anything to do with my original answer. I realize design patterns are guidelines, not rules set in stone to be implemented whenever possible. Yet I have not found a definitive explanation of the service layer and how it should be regarded. Is it a means to simply extract logic from the controller and put it inside a service instead? Is it supposed to form a contract between the controller and the domain? Should there be a layer between the domain and the service layer? And, last but not least: following the original comment Business logic should really be in a service. Not in a model. Is this correct? How would I introduce my business logic in a service instead of the model?

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• Test interface implementation

  - by Michael

  I have a interface in our code base that I would like to be able to mock out for unit testing. I am writing a test implementation to allow the individual tests to be able to override the specific methods they are concerned with rather than implementing every method. I've run into a quandary over how the test implementation should behave if the test fails to override a method used by the method under test. Should I return a "non-value" (0, null) in the test implementation or throw a UnsupportedOperationException to explicitly fail the test?

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• How to create a fountain in UDK

  - by user36425

  I'm trying to make a fountain in my level in UDK, I made the base of the fountain by using a Cylinder build and now I'm trying to put water in it. I went to use the fluidSurfaceActor but I notice that this is square but my fountain is a cylinder. Is there a way that I can change the shape of the fluidSurfaceActor to fit the builder brush shape or is there another way to do this? Or is it hopeless and I have to make my fountain into a cube? Here is a link/picture to the screenprint of what I'm talking about:

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• ACE a Session at Oracle OpenWorld

  - by Oracle OpenWorld Blog Team

  By Bob Rhubart Oracle ACE Sessions at Oracle OpenWorldAs you're finalizing your Oracle OpenWorld travel plans and taking advantage of Schedule Builder to plan your week in San Francisco, make sure you add some Oracle ACE sessions to your schedule."What's an Oracle ACE?" you ask. Members of the Oracle ACE Program are the most active members of the Oracle community, frequently sharing their substantial insights and real-world expertise with Oracle technologies through articles, blogs, social networks, and as presenters at Oracle OpenWorld and other events.With so many great sessions at this year's event, building your schedule can involve making a lot of tough choices. But you'll find that the sessions led by Oracle ACEs will be the icing on the cake of your Oracle OpenWorld content experience.To see a full list of Oracle ACE sessions at Oracle OpenWorld and other Oracle conferences that same week, check out this blog post that lists them all.

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• WWDC 2010 : Apple a présenté la nouvelle version de XCode, l'environnement de développement d'Apple

  Apple a dévoilé la nouvelle version de XCode 4 aux développeurs présents à l'édition 2010 de la WWDC. Seuls les développeurs inscrits à la WWDC peuvent actuellement télécharger XCode 4 sur leur Mac. XCode 4 nécessite Mac OS X 10.6.4 Qu'apporte-t-il de neuf ? On ne sait pas encore grand chose, vu que tout ce qui se passe à la WWDC en dehors de la keynote est sous NDA. Mais, malgré la NDA, quelques bruits filtrent sur le net. Il semblerait que XCode 4 apporterait un meilleur support pour le versionning du code. Où on aurait une interface à la Time Machine pour merger son code facilement. Meilleure intégration avec SubVersion, Git. Interface Builder ne serait plus quelque chose qui est à ...

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• Pluggable Rules for Entity Framework Code First

  - by Ricardo Peres

  Suppose you want a system that lets you plug custom validation rules on your Entity Framework context. The rules would control whether an entity can be saved, updated or deleted, and would be implemented in plain .NET. Yes, I know I already talked about plugable validation in Entity Framework Code First, but this is a different approach. An example API is in order, first, a ruleset, which will hold the collection of rules: 1: public interface IRuleset : IDisposable 2: { 3: void AddRule<T>(IRule<T> rule); 4: IEnumerable<IRule<T>> GetRules<T>(); 5: } Next, a rule: 1: public interface IRule<T> 2: { 3: Boolean CanSave(T entity, DbContext ctx); 4: Boolean CanUpdate(T entity, DbContext ctx); 5: Boolean CanDelete(T entity, DbContext ctx); 6: String Name 7: { 8: get; 9: } 10: } Let’s analyze what we have, starting with the ruleset: Only has methods for adding a rule, specific to an entity type, and to list all rules of this entity type; By implementing IDisposable, we allow it to be cancelled, by disposing of it when we no longer want its rules to be applied. A rule, on the other hand: Has discrete methods for checking if a given entity can be saved, updated or deleted, which receive as parameters the entity itself and a pointer to the DbContext to which the ruleset was applied; Has a name property for helping us identifying what failed. A ruleset really doesn’t need a public implementation, all we need is its interface. The private (internal) implementation might look like this: 1: sealed class Ruleset : IRuleset 2: { 3: private readonly IDictionary<Type, HashSet<Object>> rules = new Dictionary<Type, HashSet<Object>>(); 4: private ObjectContext octx = null; 5:  6: internal Ruleset(ObjectContext octx) 7: { 8: this.octx = octx; 9: } 10:  11: public void AddRule<T>(IRule<T> rule) 12: { 13: if (this.rules.ContainsKey(typeof(T)) == false) 14: { 15: this.rules[typeof(T)] = new HashSet<Object>(); 16: } 17:  18: this.rules[typeof(T)].Add(rule); 19: } 20:  21: public IEnumerable<IRule<T>> GetRules<T>() 22: { 23: if (this.rules.ContainsKey(typeof(T)) == true) 24: { 25: foreach (IRule<T> rule in this.rules[typeof(T)]) 26: { 27: yield return (rule); 28: } 29: } 30: } 31:  32: public void Dispose() 33: { 34: this.octx.SavingChanges -= RulesExtensions.OnSaving; 35: RulesExtensions.rulesets.Remove(this.octx); 36: this.octx = null; 37:  38: this.rules.Clear(); 39: } 40: } Basically, this implementation: Stores the ObjectContext of the DbContext to which it was created for, this is so that later we can remove the association; Has a collection - a set, actually, which does not allow duplication - of rules indexed by the real Type of an entity (because of proxying, an entity may be of a type that inherits from the class that we declared); Has generic methods for adding and enumerating rules of a given type; Has a Dispose method for cancelling the enforcement of the rules. A (really dumb) rule applied to Product might look like this: 1: class ProductRule : IRule<Product> 2: { 3: #region IRule<Product> Members 4:  5: public String Name 6: { 7: get 8: { 9: return ("Rule 1"); 10: } 11: } 12:  13: public Boolean CanSave(Product entity, DbContext ctx) 14: { 15: return (entity.Price > 10000); 16: } 17:  18: public Boolean CanUpdate(Product entity, DbContext ctx) 19: { 20: return (true); 21: } 22:  23: public Boolean CanDelete(Product entity, DbContext ctx) 24: { 25: return (true); 26: } 27:  28: #endregion 29: } The DbContext is there because we may need to check something else in the database before deciding whether to allow an operation or not. And here’s how to apply this mechanism to any DbContext, without requiring the usage of a subclass, by means of an extension method: 1: public static class RulesExtensions 2: { 3: private static readonly MethodInfo getRulesMethod = typeof(IRuleset).GetMethod("GetRules"); 4: internal static readonly IDictionary<ObjectContext, Tuple<IRuleset, DbContext>> rulesets = new Dictionary<ObjectContext, Tuple<IRuleset, DbContext>>(); 5:  6: private static Type GetRealType(Object entity) 7: { 8: return (entity.GetType().Assembly.IsDynamic == true ? entity.GetType().BaseType : entity.GetType()); 9: } 10:  11: internal static void OnSaving(Object sender, EventArgs e) 12: { 13: ObjectContext octx = sender as ObjectContext; 14: IRuleset ruleset = rulesets[octx].Item1; 15: DbContext ctx = rulesets[octx].Item2; 16:  17: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Added)) 18: { 19: Object entity = entry.Entity; 20: Type realType = GetRealType(entity); 21:  22: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 23: { 24: if (rule.CanSave(entity, ctx) == false) 25: { 26: throw (new Exception(String.Format("Cannot save entity {0} due to rule {1}", entity, rule.Name))); 27: } 28: } 29: } 30:  31: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted)) 32: { 33: Object entity = entry.Entity; 34: Type realType = GetRealType(entity); 35:  36: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 37: { 38: if (rule.CanDelete(entity, ctx) == false) 39: { 40: throw (new Exception(String.Format("Cannot delete entity {0} due to rule {1}", entity, rule.Name))); 41: } 42: } 43: } 44:  45: foreach (ObjectStateEntry entry in octx.ObjectStateManager.GetObjectStateEntries(EntityState.Modified)) 46: { 47: Object entity = entry.Entity; 48: Type realType = GetRealType(entity); 49:  50: foreach (dynamic rule in (getRulesMethod.MakeGenericMethod(realType).Invoke(ruleset, null) as IEnumerable)) 51: { 52: if (rule.CanUpdate(entity, ctx) == false) 53: { 54: throw (new Exception(String.Format("Cannot update entity {0} due to rule {1}", entity, rule.Name))); 55: } 56: } 57: } 58: } 59:  60: public static IRuleset CreateRuleset(this DbContext context) 61: { 62: Tuple<IRuleset, DbContext> ruleset = null; 63: ObjectContext octx = (context as IObjectContextAdapter).ObjectContext; 64:  65: if (rulesets.TryGetValue(octx, out ruleset) == false) 66: { 67: ruleset = rulesets[octx] = new Tuple<IRuleset, DbContext>(new Ruleset(octx), context); 68: 69: octx.SavingChanges += OnSaving; 70: } 71:  72: return (ruleset.Item1); 73: } 74: } It relies on the SavingChanges event of the ObjectContext to intercept the saving operations before they are actually issued. Yes, it uses a bit of dynamic magic! Very handy, by the way! So, let’s put it all together: 1: using (MyContext ctx = new MyContext()) 2: { 3: IRuleset rules = ctx.CreateRuleset(); 4: rules.AddRule(new ProductRule()); 5:  6: ctx.Products.Add(new Product() { Name = "xyz", Price = 50000 }); 7:  8: ctx.SaveChanges(); //an exception is fired here 9:  10: //when we no longer need to apply the rules 11: rules.Dispose(); 12: } Feel free to use it and extend it any way you like, and do give me your feedback! As a final note, this can be easily changed to support plain old Entity Framework (not Code First, that is), if that is what you are using.

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• Tömörítés becslése - Compression Advisor

  - by lsarecz

  Az Oracle Database 11g verziójától már OLTP adatbázisok is hatékonyan tömöríthetok az Advanced Compression funkcióval. Nem csak a tárolandó adatok mennyisége csökken ezáltal felére, vagy akár negyedére, de az adatbázis teljesítménye is javulhat, amennyiben I/O korlátos a rendszer (és általában az). Hogy pontosan mekkora tömörítés várható az Advanced Compression bevezetésével, az kiválóan becsülheto a Compression Advisor eszközzel. Ez nem csak az OLTP tömörítés mértékét, de 11gR2 verziótól kezdve a HCC tömörítés arányát is becsülni tudja, amely Exadata Database Machine, Pillar Axiom illetve ZFS Storage alkalmazásával érheto el. A HCC tömörítés becsléséhez csak 11gR2 adatbázisra van szükség, nem kell hozzá a speciális célhardver (Exadata, Pillar, ZFS). A Compression Advisor valójában a DBMS_COMPRESSION package használatával érheto el. A package-hez tartozik 6 konstans, amellyel a kívánt tömörítési szintek választhatók ki: Constant Type Value Description COMP_NOCOMPRESS NUMBER 1 No compression COMP_FOR_OLTP NUMBER 2 OLTP compression COMP_FOR_QUERY_HIGH NUMBER 4 High compression level for query operations COMP_FOR_QUERY_LOW NUMBER 8 Low compression level for query operations COMP_FOR_ARCHIVE_HIGH NUMBER 16 High compression level for archive operations COMP_FOR_ARCHIVE_LOW NUMBER 32 Low compression level for archive operations A GET_COMPRESSION_RATIO tárolt eljárás elemzi a tömöríteni kívánt táblát. Mindig csak egy táblát, vagy opcionálisan annak egy partícióját tudja elemezni úgy, hogy a tábláról készít egy másolatot egy külön erre a célra kijelölt/létrehozott táblatérre. Amennyiben az elemzést egyszerre több tömörítési szintre futtatjuk, úgy a tábláról annyi másolatot készít. A jó közelítésu becslés (+-5%) feltétele, hogy táblánként/partíciónként minimum 1 millió sor legyen. 11gR1 esetében még a DBMS_COMP_ADVISOR csomag GET_RATIO eljárása volt használatos, de ez még nem támogatta a HCC becslést. Érdemes még megnézni és kipróbálni a Tyler Muth blogjában publikált formázó eszközt, amivel a compression advisor kimenete alakítható jól értelmezheto formátumúvá. Végül összegezném mit is tartalmaz az Advanced Compression opció, mivel gyakran nem világos a felhasználóknak miért kell fizetni: Data Guard Network Compression Data Pump Compression (COMPRESSION=METADATA_ONLY does not require the Advanced Compression option) Multiple RMAN Compression Levels (RMAN DEFAULT COMPRESS does not require the Advanced Compression option) OLTP Table Compression SecureFiles Compression and Deduplication Ez alapján RMAN esetében például a default compression (BZIP2) szint ingyen használható, viszont az új ZLIB Advanced Compression opciót igényel. A ZLIB hatékonyabban használja a CPU-t, azaz jóval gyorsabb, viszont kisebb tömörítési arány érheto el vele.

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• Dynamically changing DVT Graph at Runtime

  - by mona.rakibe(at)oracle.com

  I recently came across this requirement where the customer wanted to change the graph type at run-time based on some selection. After some internal discussions we realized this can be best achieved by using af:switcher to toggle between multiple graphs. In this blog I will be sharing the sample that I build to demonstrate this.[Note] : In the below sample, every-time user changes graph type there is a server trip, so please use this approach with performance implications in mind.This sample can be downloaded  from DynamicGraph.zipSet-up: Create a BAM data control using employees DO (sample)(Refer this entry)Steps:Create the View Create a new JSF page .From component palette drag and drop "Select One Radio" into this page Enter some Label and click "Finish"In Property Editor set the "AutoSubmit" property to trueNow drag and drop "Switcher" from components into this page.In the Structure pane select the af:switcher right click and surround with "PanelGroupLayout"In Property Editor set the "PartialTriggers"  property of PanelGroupLayout to the id of af:selectOneRadioAgain in the Structure pane select the af:switcher right click and select "Insert inside af:switcher->facet"Enter Facet name (ex: pie)Again in the Structure pane select the af:switcher right click and select "Insert inside af:switcher->facet" Enter  another Facet name (ex: bar)From "Data Controls" drag and drop "Employees->Query"  into the pie facet as "Graph->Pie" (Pie: Sales_Number and Slices: Salesperson)From "Data Controls" drag and drop "Employees->Query"  into the bar facet as "Graph->Bar" (Bars :Sales_Number and X-axis : Salesperson).Now wire the switcher to the af:selectOneRadio using their "facetName" and "value" property respectively.Now run the page, notice that graph renders as per the selection by user.

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• Blazing Keywords - The Google Blazing Keywords Review

  Many people who are currently attempting different methods of online marketing in order to promote and build their business have heard that keyword research is extremely vital to the success of your online marketing. Unfortunately most online marketing companies do not properly teach their members how to effectively do their keyword research in order to get good results and because of that many people are left to look for services that promise to do this for them.

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• How do I fix Handbrake mp4s that produce Error -2041 when loaded in QuickTime?

  - by magnifico

  After encoding a DVD video to MP4 using Handbrake 0.9.4(2009112300) using the High Profile preset, my video will not open in QuickTime. I receive the following error: Error -2041: An invalid sample description was found in the movie (Movie.mp4) Here is the preset used to encode the video: <Preset> <Category>Regular</Category> <Name>High Profile</Name> <Query>-e x264 -q 20.0 -a 1,1 -E faac,ac3 -B 160,160 -6 dpl2,auto -R 48,Auto -D 0.0,0.0 -f mp4 --detelecine --decomb --loose-anamorphic -m -x b-adapt=2:rc-lookahead=50</Query> <PictureSettings>true</PictureSettings> <Version>0.9.4</Version> </Preset> How can I adjust this preset or fix the files so that they will play in QuickTime?

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• How to filter a mysql database with user input on a website and then spit the filtered table back to the website? [migrated]

  - by Luke

  I've been researching this on google for literally 3 weeks, racking my brain and still not quite finding anything. I can't believe this is so elusive. (I'm a complete beginner so if my terminology sounds stupid then that's why.) I have a database in mysql/phpmyadmin on my web host. I'm trying to create a front end that will allow a user to specify criteria for querying the database in a way that they don't have to know sql, basically just combo boxes and checkboxes on a form. Then have this form 'submit' a query to the database, and show the filtered tables. This is how the SQL looks in Microsoft Access: PARAMETERS TEXTINPUT1 Text ( 255 ), NUMBERINPUT1 IEEEDouble; // pops up a list of parameters for the user to input SELECT DISTINCT Table1.Column1, Table1.Column2, Table1.Column3,* // selects only the unique rows in these three columns FROM Table1 // the table where this query is happening WHERE (((Table1.Column1) Like TEXTINPUT1] AND ((Table1.Column2)<=[NUMBERINPUT1] AND ((Table1.Column3)>=[NUMBERINPUT1])); // the criteria for the filter, it's comparing the user input parameters to the data in the rows and only selecting matches according to the equal sign, or greater than + equal sign, or less than + equal sign What I don't get: WHAT IN THE WORLD AM I SUPPOSED TO USE (that isn't totally hard)!? I've tried google fusion tables - doesn't filter right with numerical data or empty cells in rows, can't relate tables I've tried DataTables.net, can't filter right with numerical data and can't use SQL without a bunch of indepth knowledge, not even sure it can if you have that.. I've looked into using jQuery with google spreadsheets, doesn't work at all either I have no idea how I'm supposed to build a front end with my database. Every place that looks promising (like zohocreator) is asking for money, and is far too simplified to be able to do the LIKE criteria or SELECT DISTINCT stuff.

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• What do you do before you start programming?

  - by SterAllures

  Heya, I'm not sure this question belongs here, it's not so much I problem I'm having with programming but rather a problem of what to do before I start programming. I want a visual representation of what variables I need and what classes have what methods.I know there is UML but I'm not sure if that is the best way, so what do you guys use before you start programming, which method? I don't want to start a flamewar about what is better just what are several approaches?

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• What is the correct term for - server/client database sync via API?

  - by Daniel

  Forgive the vague question title. I've been programming mobile apps for 3 years now, and I've got a little too far from the web services and server side code then I probably should have. Anyway, I'm doing a personal project now and I want to create an web API for it. One of my requirements is to check for updates from my app, so I would send a timestamp to the API. I've used many APIs that my clients prepared for me and only now am I appreciating their work ! What is the term or technique used to create an API backed by a database which tracks changes via dates/timestamps, basically an effective way for me to query changes occurring since a timestamp. Simply put, I want that my app can call my API in order to sync new data and changed data from the server, to the app. The app would only have a timestamp of the last time it synced with the server. Would I have a log table for each data table in my database which adds a record for each change? Then I could query all changes with a timestamp superior to the one passed to the API. Can anyone point me in the right direction on this?

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• More Fun with C# Iterators and Generators

  - by James Michael Hare

  In my last post, I talked quite a bit about iterators and how they can be really powerful tools for filtering a list of items down to a subset of items.  This had both pros and cons over returning a full collection, which, in summary, were:   Pros: If traversal is only partial, does not have to visit rest of collection. If evaluation method is costly, only incurs that cost on elements visited. Adds little to no garbage collection pressure.    Cons: Very slight performance impact if you know caller will always consume all items in collection. And as we saw in the last post, that con for the cost was very, very small and only really became evident on very tight loops consuming very large lists completely.    One of the key items to note, though, is the garbage!  In the traditional (return a new collection) method, if you have a 1,000,000 element collection, and wish to transform or filter it in some way, you have to allocate space for that copy of the collection.  That is, say you have a collection of 1,000,000 items and you want to double every item in the collection.  Well, that means you have to allocate a collection to hold those 1,000,000 items to return, which is a lot especially if you are just going to use it once and toss it.   Iterators, though, don't have this problem.  Each time you visit the node, it would return the doubled value of the node (in this example) and not allocate a second collection of 1,000,000 doubled items.  Do you see the distinction?  In both cases, we're consuming 1,000,000 items.  But in one case we pass back each doubled item which is just an int (for example's sake) on the stack and in the other case, we allocate a list containing 1,000,000 items which then must be garbage collected.   So iterators in C# are pretty cool, eh?  Well, here's one more thing a C# iterator can do that a traditional "return a new collection" transformation can't!   It can return **unbounded** collections!   I know, I know, that smells a lot like an infinite loop, eh?  Yes and no.  Basically, you're relying on the caller to put the bounds on the list, and as long as the caller doesn't you keep going.  Consider this example:   public static class Fibonacci {     // returns the infinite fibonacci sequence     public static IEnumerable<int> Sequence()     {         int iteration = 0;         int first = 1;         int second = 1;         int current = 0;         while (true)         {             if (iteration++ < 2)             {                 current = 1;             }             else             {                 current = first + second;                 second = first;                 first = current;             }             yield return current;         }     } }   Whoa, you say!  Yes, that's an infinite loop!  What the heck is going on there?  Yes, that was intentional.  Would it be better to have a fibonacci sequence that returns only a specific number of items?  Perhaps, but that wouldn't give you the power to defer the execution to the caller.   The beauty of this function is it is as infinite as the sequence itself!  The fibonacci sequence is unbounded, and so is this method.  It will continue to return fibonacci numbers for as long as you ask for them.  Now that's not something you can do with a traditional method that would return a collection of ints representing each number.  In that case you would eventually run out of memory as you got to higher and higher numbers.  This method, though, never runs out of memory.   Now, that said, you do have to know when you use it that it is an infinite collection and bound it appropriately.  Fortunately, Linq provides a lot of these extension methods for you!   Let's say you only want the first 10 fibonacci numbers:       foreach(var fib in Fibonacci.Sequence().Take(10))     {         Console.WriteLine(fib);     }   Or let's say you only want the fibonacci numbers that are less than 100:       foreach(var fib in Fibonacci.Sequence().TakeWhile(f => f < 100))     {         Console.WriteLine(fib);     }   So, you see, one of the nice things about iterators is their power to work with virtually any size (even infinite) collections without adding the garbage collection overhead of making new collections.    You can also do fun things like this to make a more "fluent" interface for for loops:   // A set of integer generator extension methods public static class IntExtensions {     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> Every(this int start)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; ++i)         {             yield return i;         }     }     // Begins counting to infinity by the given step value, use To() to     public static IEnumerable<int> Every(this int start, int byEvery)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; i += byEvery)         {             yield return i;         }     }     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> To(this int start, int end)     {         for (var i = start; i <= end; ++i)         {             yield return i;         }     }     // Ranges the count by specifying the upper range of the count.     public static IEnumerable<int> To(this IEnumerable<int> collection, int end)     {         return collection.TakeWhile(item => item <= end);     } }   Note that there are two versions of each method.  One that starts with an int and one that starts with an IEnumerable<int>.  This is to allow more power in chaining from either an existing collection or from an int.  This lets you do things like:   // count from 1 to 30 foreach(var i in 1.To(30)) {     Console.WriteLine(i); }     // count from 1 to 10 by 2s foreach(var i in 0.Every(2).To(10)) {     Console.WriteLine(i); }     // or, if you want an infinite sequence counting by 5s until something inside breaks you out... foreach(var i in 0.Every(5)) {     if (someCondition)     {         break;     }     ... }     Yes, those are kinda play functions and not particularly useful, but they show some of the power of generators and extension methods to form a fluid interface.   So what do you think?  What are some of your favorite generators and iterators?

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• Remote Data connection in iphone app

  - by Tariq- iPHONE Programmer

  Hello, i am working with Social Networking iphone app which require remote data connection. So i hired a php developer in order to provide me RESTful services. But when i start working with him, he arguing me that he will not make stored procedures and web services. Instead of he suggested me to pass query as a parameter. Suppose If I have to call Search service, he told me to send POST request with 3 parameters: Query="select * from users", username=abd and password = 123 And i thing there is no such architecture in order to use remote data. Then he is saying it is possible through socket programming. And I am 100% sure this is not an appropriate way to access remote data. This is simply illogical. Thousands of iphone application using REST/SOAP services to make remote data connection He just declined me to provide RESTful services. Please its my heartily advice to all developers that post your own views over here. So that I can show to that developers that these are the views from all developers worldwide.

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• Which web framework to use under Backbonejs?

  - by egidra

  For a previous project, I was using Backbonejs alongside Django, but I found out that I didn't use many features from Django. So, I am looking for a lighter framework to use underneath a Backbonejs web app. I never used Django built in templates. When I did, it was to set up the initial index page, but that's all. I did use the user management system that Django provided. I used the models.py, but never views.py. I used urls.py to set up which template the user would hit upon visiting the site. I noticed that the two features that I used most from Django was South and Tastypie, and they aren't even included with Django. Particularly, django-tastypie made it easy for me to link up my frontend models to my backend models. It made it easy to JSONify my front end models and send them to Tastypie. Although, I found myself overriding a lot of tastypie's methods for GET, PUT, POST requests, so it became useless. South made it easy to migrate new changes to the database. Although, I had so much trouble with South. Is there a framework with an easier way of handling database modifications than using South? When using South with multiple people, we had the worse time keeping our databases synced. When someone added a new table and pushed their migration to git, the other two people would spend days trying to use South's automatic migration, but it never worked. I liked how Rails had a manual way of migrating databases. Even though I used Tastypie and South a lot, I found myself not actually liking them because I ended up overriding most Tastypie methods for each Resource, and I also had the worst trouble migrating new tables and columns with South. So, I would like a framework that makes that process easier. Part of my problem was that they are too "magical". Which framework should I use? Nodejs or a lighter Python framework? Which works best with my above criteria?

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• Back up a single table in SQL Server

  - by BuckWoody

  SQL Server doesn’t have an easy way to take a table backup, so I often use the bcp (Bulk Copy Program) to accomplish the same goal. I’ve mentioned this before, and someone told me when they tried it they couldn’t restore the table – ah the dangers of telling people half the information! I should have mentioned that you need to have a “format file” ready if the table does not exist at the destination. In my case I already had the table, in this person’s case they did not. The format file can be used to rebuild that table structure before the data is bcp’d in, and you can read more about it here: http://msdn.microsoft.com/en-us/library/ms191516.aspx There’s another way to back up a table, and that’s to create a Filegroup and place the table there. Then you can take a Filegroup backup to back up a single table. Of course, there are other methods of moving a single table’s data in an out, including SQL Server Integration Services and even the older Data Transformation Services, or simply by using hte SQLCMD or PowerShell utilities to run a query and just save the output to a file. In fact, these days I’m using a PowerShell script to build INSERT statements from that query. That could also easily be modified to create the table structure (or modify one if needed) quite easily. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• C#/.NET Little Wonders: Use Cast() and TypeOf() to Change Sequence Type

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. We’ve seen how the Select() extension method lets you project a sequence from one type to a new type which is handy for getting just parts of items, or building new items.  But what happens when the items in the sequence are already the type you want, but the sequence itself is typed to an interface or super-type instead of the sub-type you need? For example, you may have a sequence of Rectangle stored in an IEnumerable<Shape> and want to consider it an IEnumerable<Rectangle> sequence instead.  Today we’ll look at two handy extension methods, Cast<TResult>() and OfType<TResult>() which help you with this task. Cast<TResult>() – Attempt to cast all items to type TResult So, the first thing we can do would be to attempt to create a sequence of TResult from every item in the source sequence.  Typically we’d do this if we had an IEnumerable<T> where we knew that every item was actually a TResult where TResult inherits/implements T. For example, assume the typical Shape example classes: 1: // abstract base class 2: public abstract class Shape { } 3:  4: // a basic rectangle 5: public class Rectangle : Shape 6: { 7: public int Widtgh { get; set; } 8: public int Height { get; set; } 9: } And let’s assume we have a sequence of Shape where every Shape is a Rectangle… 1: var shapes = new List<Shape> 2: { 3: new Rectangle { Width = 3, Height = 5 }, 4: new Rectangle { Width = 10, Height = 13 }, 5: // ... 6: }; To get the sequence of Shape as a sequence of Rectangle, of course, we could use a Select() clause, such as: 1: // select each Shape, cast it to Rectangle 2: var rectangles = shapes 3: .Select(s => (Rectangle)s) 4: .ToList(); But that’s a bit verbose, and fortunately there is already a facility built in and ready to use in the form of the Cast<TResult>() extension method: 1: // cast each item to Rectangle and store in a List<Rectangle> 2: var rectangles = shapes 3: .Cast<Rectangle>() 4: .ToList(); However, we should note that if anything in the list cannot be cast to a Rectangle, you will get an InvalidCastException thrown at runtime.  Thus, if our Shape sequence had a Circle in it, the call to Cast<Rectangle>() would have failed.  As such, you should only do this when you are reasonably sure of what the sequence actually contains (or are willing to handle an exception if you’re wrong). Another handy use of Cast<TResult>() is using it to convert an IEnumerable to an IEnumerable<T>.  If you look at the signature, you’ll see that the Cast<TResult>() extension method actually extends the older, object-based IEnumerable interface instead of the newer, generic IEnumerable<T>.  This is your gateway method for being able to use LINQ on older, non-generic sequences.  For example, consider the following: 1: // the older, non-generic collections are sequence of object 2: var shapes = new ArrayList 3: { 4: new Rectangle { Width = 3, Height = 13 }, 5: new Rectangle { Width = 10, Height = 20 }, 6: // ... 7: }; Since this is an older, object based collection, we cannot use the LINQ extension methods on it directly.  For example, if I wanted to query the Shape sequence for only those Rectangles whose Width is > 5, I can’t do this: 1: // compiler error, Where() operates on IEnumerable<T>, not IEnumerable 2: var bigRectangles = shapes.Where(r => r.Width > 5); However, I can use Cast<Rectangle>() to treat my ArrayList as an IEnumerable<Rectangle> and then do the query! 1: // ah, that’s better! 2: var bigRectangles = shapes.Cast<Rectangle>().Where(r => r.Width > 5); Or, if you prefer, in LINQ query expression syntax: 1: var bigRectangles = from s in shapes.Cast<Rectangle>() 2: where s.Width > 5 3: select s; One quick warning: Cast<TResult>() only attempts to cast, it won’t perform a cast conversion.  That is, consider this: 1: var intList = new List<int> { 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 }; 2:  3: // casting ints to longs, this should work, right? 4: var asLong = intList.Cast<long>().ToList(); Will the code above work?  No, you’ll get a InvalidCastException. Remember that Cast<TResult>() is an extension of IEnumerable, thus it is a sequence of object, which means that it will box every int as an object as it enumerates over it, and there is no cast conversion from object to long, and thus the cast fails.  In other words, a cast from int to long will succeed because there is a conversion from int to long.  But a cast from int to object to long will not, because you can only unbox an item by casting it to its exact type. For more information on why cast-converting boxed values doesn’t work, see this post on The Dangers of Casting Boxed Values (here). OfType<TResult>() – Filter sequence to only items of type TResult So, we’ve seen how we can use Cast<TResult>() to change the type of our sequence, when we expect all the items of the sequence to be of a specific type.  But what do we do when a sequence contains many different types, and we are only concerned with a subset of a given type? For example, what if a sequence of Shape contains Rectangle and Circle instances, and we just want to select all of the Rectangle instances?  Well, let’s say we had this sequence of Shape: 1: var shapes = new List<Shape> 2: { 3: new Rectangle { Width = 3, Height = 5 }, 4: new Rectangle { Width = 10, Height = 13 }, 5: new Circle { Radius = 10 }, 6: new Square { Side = 13 }, 7: // ... 8: }; Well, we could get the rectangles using Select(), like: 1: var onlyRectangles = shapes.Where(s => s is Rectangle).ToList(); But fortunately, an easier way has already been written for us in the form of the OfType<T>() extension method: 1: // returns only a sequence of the shapes that are Rectangles 2: var onlyRectangles = shapes.OfType<Rectangle>().ToList(); Now we have a sequence of only the Rectangles in the original sequence, we can also use this to chain other queries that depend on Rectangles, such as: 1: // select only Rectangles, then filter to only those more than 2: // 5 units wide... 3: var onlyBigRectangles = shapes.OfType<Rectangle>() 4: .Where(r => r.Width > 5) 5: .ToList(); The OfType<Rectangle>() will filter the sequence to only the items that are of type Rectangle (or a subclass of it), and that results in an IEnumerable<Rectangle>, we can then apply the other LINQ extension methods to query that list further. Just as Cast<TResult>() is an extension method on IEnumerable (and not IEnumerable<T>), the same is true for OfType<T>().  This means that you can use OfType<TResult>() on object-based collections as well. For example, given an ArrayList containing Shapes, as below: 1: // object-based collections are a sequence of object 2: var shapes = new ArrayList 3: { 4: new Rectangle { Width = 3, Height = 5 }, 5: new Rectangle { Width = 10, Height = 13 }, 6: new Circle { Radius = 10 }, 7: new Square { Side = 13 }, 8: // ... 9: }; We can use OfType<Rectangle> to filter the sequence to only Rectangle items (and subclasses), and then chain other LINQ expressions, since we will then be of type IEnumerable<Rectangle>: 1: // OfType() converts the sequence of object to a new sequence 2: // containing only Rectangle or sub-types of Rectangle. 3: var onlyBigRectangles = shapes.OfType<Rectangle>() 4: .Where(r => r.Width > 5) 5: .ToList(); Summary So now we’ve seen two different ways to get a sequence of a superclass or interface down to a more specific sequence of a subclass or implementation.  The Cast<TResult>() method casts every item in the source sequence to type TResult, and the OfType<TResult>() method selects only those items in the source sequence that are of type TResult. You can use these to downcast sequences, or adapt older types and sequences that only implement IEnumerable (such as DataTable, ArrayList, etc.). Technorati Tags: C#,CSharp,.NET,LINQ,Little Wonders,TypeOf,Cast,IEnumerable<T>

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• Understanding and Benefiting from Code Contracts in .NET 4.0

  One of the fundamental programming challenges is managing state. Chances are you have written dozens and dozens of methods that at the beginning check that certain conditions are met, and that another set of conditions is met when the method returns. With Code Contracts in .NET 4.0, you can make things considerably easier. Read on to learn how.

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• http proxy caching headers

  - by David Hagan

  I have a service for which I'm about to upgrade the authentication. However, I'm trying to ensure that I make the right decision about where the encryption algorithms occur. I currently have two options: option 1) the authentication module is deployed to the client as a javascript library over https and executes client-side, so that the client can POST back an encrypted string. option 2) the authentication module is kept server-side so that the client need only POST back an unencrypted string. I know that many http proxies cache/log the query-string (and therefore any query parameters), but does anyone know of any http proxies that cache the headers as well? If the headers are being cached, then I'll clearly want to encrypt the password inside the SSL encryption, because to my understanding the headers of an HTTPS request may not always be encrypted (depending on the capabilities of the browser etcetera). Can anyone shed any light on the caching of headers by http proxies? Do you have one that does, or know of one that does?

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• The Great Ball Contraption: A Massive Automated LEGO Construction

  - by Jason Fitzpatrick

  This massive LEGO construction combines 17 distinct modules into a lengthy factory-like conveyance system for five hundred LEGO balls. The variety and creativity of the methods employed is, dare we say, dazzling. Slotted robotic arms? Screw lifts? Handshake object transfers? Catapults that shoot baskets? The sheer number of creative and novel solutions LEGO builder Akiyuky employs to move the balls through his machine left us mesmerized for the whole seven minute video. Akiyuky’s LEGO Blog (Google Translate Interpreted)[via Make] How To Create a Customized Windows 7 Installation Disc With Integrated Updates How to Get Pro Features in Windows Home Versions with Third Party Tools HTG Explains: Is ReadyBoost Worth Using?

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• Granting rights to the sa account using osql

  - by Jan Jongboom

  I'm installing sql instances through script, and after creating a certain instance, I cannot get the sa account to be enabled through osql. What I've tried osql -S .\INSTANCENAME -E use master ALTER LOGIN sa ENABLE GO Using SSMS to enable the account (by logging in using Windows Auth., 'New query', and exactly the same query as in 1.) Suggestions in this issue No. 2. is actually working; and the account is enabled instantly. No 1 is not working, not even with the suggestions provided in 3., I have restarted the SQL services after executing the commands in osql. Additional info Windows 2003 Server, Microsoft SQL Server 2005 Enterprise, No password policies apply to the account.

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• C# - How to store and reuse queries

  - by Jason Holland

  I'm learning C# by programming a real monstrosity of an application for personal use. Part of my application uses several SPARQL queries like so: const string ArtistByRdfsLabel = @" PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> SELECT DISTINCT ?artist WHERE {{ {{ ?artist rdf:type <http://dbpedia.org/ontology/MusicalArtist> . ?artist rdfs:label ?rdfsLabel . }} UNION {{ ?artist rdf:type <http://dbpedia.org/ontology/Band> . ?artist rdfs:label ?rdfsLabel . }} FILTER ( str(?rdfsLabel) = '{0}' ) }}"; string Query = String.Format(ArtistByRdfsLabel, Artist); I don't like the idea of keeping all these queries in the same class that I'm using them in so I thought I would just move them into their own dedicated class to remove clutter in my RestClient class. I'm used to working with SQL Server and just wrapping every query in a stored procedure but since this is not SQL Server I'm scratching my head on what would be the best for these SPARQL queries. Are there any better approaches to storing these queries using any special C# language features (or general, non C# specific, approaches) that I may not already know about?

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