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• Creating content for rails-based applications

  - by Matthias Hryniszak

  Hi, I'm facing a problem of cleaning up my application in Ruby on Rails. What I have is a pretty standard 3-panel, header and footer layout where different parts of the screen contain different functionality. By that I mean for example that the header contains (among others) a select that allows one to select parts of the application and a context-dependent menu. The main content area contains obviously the most interactive stuff whereas side panels contain quick-links with stuff like shopping-cart preview, list of potentially attractive products for the customer, a selector to narrow down the list of options... I was wondering how do I go about simplifying the design. Right now I have the stuff that provides data for the "common" stuff (as opposed to direct content that's placed in the center) called from all the actions (with a filter) but that doesn't feel right for me. I've read that "components" are also not the way to go for obvious performance reasons. Is there something that's more like component-oriented (other frameworks do have that kind of stuff - Grails: <ui:include ../>, ASP.NET MVC: <% Html.RenderAction() %>)? Best regards, Matthias.

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• Is NUnit's ExpectedExceptionAttribute only way to test if something raises an exception?

  - by Dariusz Walczak

  Hello, I'm completely new at C# and NUnit. In Boost.Test there is a family of BOOST_*_THROW macros. In Python's test module there is TestCase.assertRaises method. As far as I understand it, in C# with NUnit (2.4.8) the only method of doing exception test is to use ExpectedExceptionAttribute. Why should I prefer ExpectedExceptionAttribute over - let's say - Boost.Test's approach? What reasoning can stand behind this design decision? Why is that better in case of C# and NUnit? Finally, if I decide to use ExpectedExceptionAttribute, how can I do some additional tests after exception was raised and catched? Let's say that I want to test requirement saying that object has to be valid after some setter raised System.IndexOutOfRangeException. How would you fix following code to compile and work as expected? [Test] public void TestSetterException() { Sth.SomeClass obj = new SomeClass(); // Following statement won't compile. Assert.Raises( "System.IndexOutOfRangeException", obj.SetValueAt( -1, "foo" ) ); Assert.IsTrue( obj.IsValid() ); } Edit: Thanks for your answers. Today, I've found an It's the Tests blog entry where all three methods described by you are mentioned (and one more minor variation). It's shame that I couldn't find it before :-(.

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• Creating Mobile Cross-Platform Scripting Solution

  - by Aplomb

  I am having the dream to design a Mobile cross-platform scripting solution to achieve Developer only need to code once by scripting language(it's possible be Javascript or others need further investigation), then the solution will be able to generate the installation files for multiple mobile platforms like J2me, Android, Symbian, BlackBerry, Palm, Windows Mobile/Phone, iPhone, etc. Using the scripting language, developer can code with unified platform API. And other extension frameworks under scripting language, like, 1. 2D UI framework Most probably using for Mobile Applications, the UI style will compete with native UI framework and no longer every application in particular platform looks similar. 2. 3D UI framework Provide the platforms who has 3D capability can represent their Mobile Application with more fashion 3D style which will be much more abstractive. 3. Variable game engine Developers can can use it for easily and high-quality build games. 4. etc This Mobile solution is providing three points, 1. Cross-Platform 2. Scripting 3. Middleware So guys, what do you think about this idea, is it good for Developers? is it profitable? where is the better direction for this idea?

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• Is jQuery forcing Adobe ColdFusion to abandon the dead flash product line?

  - by crosenblum

  I have been reading a lot about how flash development/design had died, and as jQuery and in the near future html5 comes out, will this start to push Adobe/Coldfusion away from flash towards less product linking? I mean, I love coldfusion, and want that to continue to grow, however, if Adobe only bought Coldfusion from Macromedia, so they can bundle flash and coldfusion together, does the death of flash mean the death of coldfusion? http://topnews.us/content/221385-jobs-says-adobes-flash-waning-and-had-its-day http://aext.net/2010/03/javascript-jquery-killing-flash-tutorial-jquery-plugin/ I really don't mind if Flash dies, I do mind greatly if coldfusion does. Is the success of Flash linked to Coldfusion? If so, why? or why not? The purpose of this isn't to start some war about flash pro's and con's. I was only worried that Adobe would cause problems for Coldfusion, if flash had some market/financial problems. That was my main concern... And no I am not anti-flash... But my financial sanity depends on Coldfusion being a success, so that is why I stated my question. Because I WANT EVERYONE ELSE'S OPINION OF THIS SITUATION. Thank You.

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• JSF Templating without RAD

  - by Jeffrey Knight

  I have a set of jsp's based off a jtpl template. The template (jtpl file) looks like this: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <%-- tpl:metadata --%> <%-- jsf:codeBehind language="java" location="/JavaSource/pagecode/my.java" --%> <%-- /jsf:codeBehind --%> <%-- /tpl:metadata --%> <%@taglib uri="http://www.ibm.com/jsf/html_extended" prefix="hx"%> <%@taglib uri="http://java.sun.com/jsf/html" prefix="h"%> <HTML> <%@taglib uri="http://java.sun.com/jsf/core" prefix="f"%> <%@page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <f:view> <HEAD> ... Without using RAD, how can I change the jtpl (template) and regenerate jsp? I'm looking for a command line solution. Related question: is the jsp intended to be rendered from the template design-time in the IDE, or runtime on the server?

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• Designing DAOs around a JSON API for iPhone Development

  - by Bob Spryn

  So I've been trying to design a clean way of grabbing data for my models in iPhone land. All the data for my application is coming from JSON API's. So right now when a VC needs some models, it does the JSON call itself (asynch) and when it receives the data, it builds the models. It works, but I'm trying to think of a cleaner method whereby the DAO's retrieve the information for me and return the models, all in an async manner. My initial thought is build a protocol for my DAOs, such that the VC would instantiate a DAO and make itself the delegate. When you requested data [DAOinstance getAllUsers] the DAO would do all the network request stuff, and then when it had the data, it would call a method on its delegate (the VC) to pass the data. So I think that's a cool solution, but realized that if I needed to use the same DAO for different purposes in the same VC, my delegate method would have to branch logic depending on which DAO instance initiated the request. So my second thought was to be able to pass 'handler' selectors to the DAO object a la typical javascript patterns. So instead of an official protocol, I would say something like [DAOinstance getAllUsersWithSelector:"TheHandlerFunctionOnMyVC:"] Then when the DAO completed its network activities, it would call the passed selector on the VC, and pass the data back. So am I headed in the wrong direction entirely here? Seems like maybe an ok way to go. Any pointers or articles on designing this kind of data layer would be sweet. Thanks! Bob

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• 500 Worker Threads, what kind of thread pool?

  - by Submerged

  I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } The code that is executing is really simple and basically just this class aThread extends Thread { public void run(){ while(true){ Thread.sleep(ONE_MINUTE); //Lots of computation every minute } } } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful! Well, the design is arguably flawed. The threads implement Genetic-Programming or GP, a type of learning algorithm. Each thread analyzes advanced trends makes predictions. If the thread ever completes, the learning is lost. That said, I was hoping that sleep() would allow me to share some of the resources while one thread isn't "learning"

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• Dynamically created controls and the ASP.NET page lifecycle

  - by Dirk

  I'm working on an ASP.NET project in which the vast majority of the forms are generated dynamically at run time (form definitions are stored in a DB for customizability). Therefore, I have to dynamically create and add my controls to the Page every time OnLoad fires, regardless of IsPostBack. This has been working just fine and .NET takes care of managing ViewState for these controls. protected override void OnLoad(EventArgs e) { base.OnLoad(e); RenderDynamicControls() } private void RenderDynamicControls(){ //1. call service layer to retrieve form definition //2. create and add controls to page container } I have a new requirement in which if a user clicks on a given button (this button is created at design time) the page should be re-rendered in a slightly different way. So in addition to the code that executes in OnLoad (i.e. RenderDynamicControls()), I have this code: protected void MyButton_Click(object sender, EventArgs e) { RenderDynamicControlsALittleDifferently() } private void RenderDynamicControlsALittleDifferently() (){ //1. clear all controls from the page container added in RenderDynamicControls() //2. call service layer to retrieve form definition //3. create and add controls to page container } My question is, is this really the only way to accomplish what I'm after? It seems beyond hacky to effectively render the form twice simply to respond to a button click. I gather from my research that this is simply how the page-lifecycle works in ASP.NET: Namely, that OnLoad must fire on every Postback before child events are invoked. Still, it's worthwhile to check with the SO community before having to drink the kool-aid. On a related note, once I get this feature completed, I'm planning on throwing an UpdatePanel on the page to perform the page updates via Ajax. Any code/advice that make that transition easier would be much appreciated. Thanks

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• Voting on Hacker News stories programmatically?

  - by igorgue

  I decided to write an app like: http://michaelgrinich.com/hackernews/ but for Android devices, my idea will use a web application backend (because I rather code in Python and for the web than completely in Java for Android devices). What I have right now implemented is something like this: $ curl -i http://localhost:8080/stories.json?page=1\&stories=1 HTTP/1.0 200 OK Date: Sun, 25 Apr 2010 07:59:37 GMT Server: WSGIServer/0.1 Python/2.6.5 Content-Length: 296 Content-Type: application/json [{"title": "Don\u2019t talk to aliens, warns Stephen Hawking", "url": "http://www.timesonline.co.uk/tol/news/science/space/article7107207.ece?", "unix_time": 1272175177, "comments": 15, "score": 38, "user": "chaostheory", "position": 1, "human_time": "Sun Apr 25 01:59:37 2010", "id": "1292241"}] The next step (and final I think) is voting, my design is doing something like this: $ curl -i http://localhost:8080/stories/1?vote=up -u username:password Will vote up and: $ curl -i http://localhost:8080/stories/1?vote=down -u username:password Down. I have no idea how to do it though... I was planning to use Twill but the login link is always different, e.g.: http://news.ycombinator.com/x?fnid=7u89ccHKln Later the Android app will consume this API. Any experience with programmatically browsing Hacker News?

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• URL naming conventions

  - by LookitsPuck

  So, this may be a can of worms. But I'm curious what your practices are? For example, let's say your website consists of the following needs (very basic): A landing page An information page for an event (static) A listing of places for that event (dynamic) An information page for each place With that said, how would you design your URLs? Typically, I'd do something like the following: www.domain.com/ - landing page [also accessible via www.domain.com/home] www.domain.com/event - event information page www.domain.com/places - listing of all places www.domain.com/places/{id} - place information page Now, here's a question. Just grammatically speaking, I have a hangup of referring to a given place in a url as being plural. Shouldn't it make more sense to go with this: www.domain.com/place/{id} as opposed to www.domain.com/places/{id} In some frameworks, you have a convention to follow (for example, ASP.NET MVC) by default. Yes, you can define custom routes to have /place/{id} route to the PlacesController. However, I'm just trying to keep this a bit abstract in discussion. With that being said, let's see for instance on another page of your site, you have a link, that when clicked, would open a modal popup populated with place information. Where you place that information? We could go with something like this: www.domain.com/ajax/places/{id} OR www.domain.com/places/{id} and serve based on the request header (that is, if requesting JSON, return JSON?}. Finally, for SEO reasons, typically I use a slug associated with a given resource. So, something like such: www.domain.com/ajax/places/{id}/london Where london is only there to add decoration to the link for SEO reasons. Is this sound? I ask all of these questions, because these are practices that I've been using for awhile, and I'd just like to see what other developers are doing or if I'm approaching things incorrectly. Thanks!

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• jQuery: Stop browser scrolling on event update beyond the fold?

  - by neezer

  I have several links at the bottom of my page that update content at the top of my page (more than a viewport away). Here's the gist of what the update looks like: $('#private-photo div').fadeOut(function() { $(this).html('<%= escape_javascript(image_tag current_user.private_photo.image.url(:profile)) %>'); }).fadeIn(); Basically it's just fading out the old content and fading in the new content. My problem is that when this happens, the browser window automatically scrolls up just far enough so that the bottom of the updated content (#private-photo div) appears at the top of the browser viewport. I do not want this to happen. I want the content to be updated (still fading in and out), but without the browser viewport realigning its focus. I want to keep the animation because if the user has a big enough screen, or if they are using a link closer to the top of the page, I still want them to see the animation. Any ideas about how to prevent the browser from scrolling as described? If not, any suggestions for workarounds? FYI, I have this same problem in Safari 4, Chrome (for Mac), & Firefox 3.5. EDIT: Here's the link that calls the update action, which is itself inside a Colorbox: $('a.edit-photo').colorbox({ title: function() { return 'Edit Photo in ' + $(this).attr('rel'); }, overlayClose: false, onComplete: function() { $('#edit-photo-modal').submit(function(e) { $('#photo_submit').after('<span id="saving">Saving...</span>'); e.preventDefault(); $.post($(this).attr('action'), $(this).serialize(), function() { $('#edit-photo-modal #saving').text('Saved!'); }, "script"); }); } }); The lightbox opens, presents a form fetched through an AJAX request, then (on submit) triggers the update action mentioned above. I had these links outside of the Colorbox in an earlier design revision, and they exhibited the same problem, so I've ruled out Colorbox itself as a cause. If you need anymore info, let me know!

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• Why the composite component fails to parent controls?

  - by lyborko

  Hi, I created my own Component : TPage , which Contains Subcomponent TPaper (TPanel). The problem is, that when I put controls such as TMemo or TButton on the TPaper (which fills up nearly whole area), the controls do not load at all. see example below TPaper = class(TPanel) protected constructor Create(AOwner: TComponent);override; destructor Destroy;override; public procedure Paint; override; end; TPage = class(TCustomControl) private FPaper:TPaper; protected procedure CreateParams(var Params:TCreateParams); override; public constructor Create(AOwner: TComponent);override; destructor Destroy;override; published property Paper: TPaper read FPaper write FPaper; end; constructor TPage.Create(AOwner: TComponent); begin inherited Create(AOwner); PaperOrientation:=poPortrait; PaperSize:=psA4; PaperBrush:=TBrush.Create; PaperBrush.Color:=clWhite; PDFDocument:=Nil; FPaper:=TPaper.Create(Self); FPaper.Parent:=Self; FPaper.SetSubComponent(True); end; ... Memo1 is parented in TPaper (TPanel) at design-time, but after pressing "Run" it does not exist. procedure TForm1.btn1Click(Sender: TObject); begin if not Assigned(Memo1) then ShowMessage('I do not exist'); //Memo1 is nil end; Have you any idea what's wrong? Thanks a lot P.S Delphi 7 When I put TMemo inside TPaper and save the unit (Unit1), after inspection of associated dfm file, there is no trace of TMemo component. (Thats why it can not load to app.)

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• SQL, MVC, Entity Framework

  - by Anthony

  Hi Im using the above technologies and have ran into what I presume is a design issue I have made. I have an Artwork table in my DB and have been able to add art (I now think of these as Digital Products) to a shopping cart + CartLine table fine. The system I have that adds art to galleries and user accounts etc works fine. Now the client wants to sell T-shirts, Mugs and Pens etc, 'HardwareProducts' so I have created a 'HardwareProducts' table. Now I have two different product types in two tables. I use GUID's as the PK's in both the HardwareProducts table and Artwork table. When a customer adds an item to their cart I store the GUID in the ProductID column in the CartItems table. The issue is the database will not know which table to reference when I bring the LineItem object up through my ORM to the front end. In OOP I can see how you would have a base class of Product, and then a DigitalProduct class and HardwareProduct class drived from it, but how do you model this in SQL Server and the Entity Framework please, or is there another way?

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• Refactor throwing not null exception if using a method that has a dependency on a certain contructor

  - by N00b

  In the method below the second constructor accepts a ForumThread object which the IncrementViewCount() method uses. There is a dependency between the method and that particular constructor. Without extracting into a new private method the null check in IncrementViewCount() and LockForumThread() (plus other methods not shown) is there some simpler re-factoring I can do or the implementation of a better design practice for this method to guard against the use of the wrong constructor with these dependent methods? Thank you for any suggestions in advance. private readonly IThread _forumLogic; private readonly ForumThread _ft; public ThreadLogic(IThread forumLogic) : this(forumLogic, null) { } public ThreadLogic(IThread forumLogic, ForumThread ft) { _forumLogic = forumLogic; _ft = ft; } public void Create(ForumThread ft) { _forumLogic.SaveThread(ft); } public void IncrementViewCount() { if (_ft == null) throw new NoNullAllowedException("_ft ForumThread is null; this must be set in the constructor"); lock (_ft) { _ft.ViewCount = _ft.ViewCount + 1; _forumLogic.SaveThread(_ft); } } public void LockForumThread() { if (_ft == null) throw new NoNullAllowedException("_ft ForumThread is null; this must be set in the constructor"); _ft.ThreadLocked = true; _forumLogic.SaveThread(_ft); }

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• Why use Entity Framework over Linq2SQL ...

  - by Refracted Paladin

  To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason to use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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• Forward declaration of derived inner class

  - by Loom

  I ran into problem implementing some variations of factory method. // from IFoo.h struct IFoo { struct IBar { virtual ~IBar() = 0; virtual void someMethod() = 0; }; virtual IBar *createBar() = 0; }; // from Foo.h struct Foo : IFoo { // implementation of Foo, Bar in Foo.cpp struct Bar : IBar { virtual ~Bar(); virtual void someMethod(); }; virtual Bar *createBar(); // implemented in Foo.cpp }; I'd like to place declaration of Foo::Bar in Foo.cpp. For now I cannot succeed: struct Foo : IFoo { //struct Bar; //1. error: invalid covariant return type // for ‘virtual Foo::Bar* //struct Bar : IBar; //2. error: expected ‘{’ before ‘;’ token virtual Bar *createBar(); // virtual IBar *createBar(); // Is not acceptable by-design }; Is there a trick to have just forward declaration of Boo in Foo.hpp and to have full declaration in Foo.cpp?

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• Recommend me an architecture for this Facebook application

  - by andybaird

  Firstly, this question is subjective. There is not a right answer for this question and it really depends on what works for you. I'm hoping to use this thread as a breeding ground for ideas. I hope this is acceptable in this medium. I'm working on building a Facebook app that will be replacing an already popular app that gets ~50k hits a day. The original app is using a very typical LAMP setup with help from some Zend libraries for database layer extraction. For the most part the app worked well, except to solve a lot of issues I ended up fragmenting tables to speed things up. As a result, I couldn't do a lot of things with the app that I wanted to (namely any processing using aggregate data that needed to be returned quickly) So I'm starting to design plans for the next version of this application, and I have a whole bunch of new and cool features that I know would choke my current setup. I'm looking for technological recommendations of data storage methods that scale well. The database does not necessarily need to be relational, simple key/value storage would suffice (although at present time I know little to nothing about KV stores) What's your recommendation? How would you tackle this? I'd like to take a completely free approach to this -- although I am most familiar and comfortable using PHP, I want to leave all technical options open.

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• Volatile fields in C#

  - by Danny Chen

  From the specification 10.5.3 Volatile fields: The type of a volatile field must be one of the following: A reference-type. The type byte, sbyte, short, ushort, int, uint, char, float, bool, System.IntPtr, or System.UIntPtr. An enum-type having an enum base type of byte, sbyte, short, ushort, int, or uint. First I want to confirm my understanding is correct: I guess the above types can be volatile because they are stored as a 4-bytes unit in memory(for reference types because of its address), which guarantees the read/write operation is atomic. A double/long/etc type can't be volatile because they are not atomic reading/writing since they are more than 4 bytes in memory. Is my understanding correct? And the second, if the first guess is correct, why a user defined struct with only one int field in it(or something similar, 4 bytes is ok) can't be volatile? Theoretically it's atomic right? Or it's not allowed simply because that all user defined structs(which is possibly more than 4 bytes) are not allowed to volatile by design?

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• Advanced All In One .NET Framework

  - by alfredo dobrekk

  Hi, i m starting a new project that would basically take input from user and save them to database among about 30 screens, and i would like to find a framework that will allow the maximum number of these features out of the box : .net c#. windows form. unit testing continuous integration screens with lists, combo boxes, text boxes, add, delete, save, cancel that are easy to update when you add a property to your classes or a field to your database. auto completion on controls to help user find its way use of an orm like nhibernate easy multithreading and display of wait screens for user easy undo redo tabbed child windows search forms ability to grant access to some functionnalities according to user profiles mvp/mvvm or whatever design patterns either some code generation from database to c# classe or generation of database schema from c# classes some kind of database versioning / upgrade to easily update database when i release patches to application once in production automatic control resizing code metrics analysis some code generator i can use against my entities that would generate some rough form i can rearrange after code documentation generator ... Any ideas ? I know its lot but i really would like to use existing code to build upon so i can focus on business rules. Could splitting the requirements on 3 or 4 existing open source framework be possible ? Do u have any suggestion to add to the list before starting ? What open source tools would u use to achieve these ?

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• Bespoke Development or Leverage SharePoint With Web Parts etc?

  - by Asim

  Hi all, We are currently in the process of drawing up a solution for an existing client, creating a number of eServices. The client currently have MOSS 2007. The proposed solution is to use MOSS as the launching pad for the eServices… The requirement involves drawing up several online forms which provide registration facilities as well as facilitating a workflow of some sort. I have been told that the proposed solution requires complex web forms. Most are complex forms with parent child details that have multiple windows. The proposed solution is to do some bespoke development, developing ASP .NET forms. These forms would be deployed under the _layouts folder of the current MOSS portal, inheriting the master page design on the current site. I have been told that this approach make development and deployment more simple, as well has having ‘complete integration’ with MOSS. My questions are: Is this the best way to leverage SharePoint – it seems like the proposed solution is not leveraging MOSS at all..! I thought perhaps utilizing Web Parts would be better, but I have been told that this is more complex and developing more smarter intuitive UI is more difficult. Is this really the case? If not, what should be the recommended approach? We will be utilizing Ultimus as the workflow engine. However, I have been recommended K2 Workflows. Anyone used both/have any opinions on either? Many thanks in advance! Kind Regards,

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• Is my method for avoiding dynamic_cast<> faster than dynamic_cast<> itself ?

  - by ereOn

  Hi, I was answering a question a few minutes ago and it raised to me another one: In one of my projects, I do some network message parsing. The messages are in the form of: [1 byte message type][2 bytes payload length][x bytes payload] The format and content of the payload are determined by the message type. I have a class hierarchy, based on a common class Message. To instanciate my messages, i have a static parsing method which gives back a Message* depending on the message type byte. Something like: Message* parse(const char* frame) { // This is sample code, in real life I obviously check that the buffer // is not NULL, and the size, and so on. switch(frame[0]) { case 0x01: return new FooMessage(); case 0x02: return new BarMessage(); } // Throw an exception here because the mesage type is unknown. } I sometimes need to access the methods of the subclasses. Since my network message handling must be fast, I decived to avoid dynamic_cast<> and I added a method to the base Message class that gives back the message type. Depending on this return value, I use a static_cast<> to the right child type instead. I did this mainly because I was told once that dynamic_cast<> was slow. However, I don't know exactly what it really does and how slow it is, thus, my method might be as just as slow (or slower) but far more complicated. What do you guys think of this design ? Is it common ? Is it really faster than using dynamic_cast<> ? Any detailed explanation of what happen under the hood when one use dynamic_cast<> is welcome !

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• Segmentation in Linux : Segmentation & Paging are redundant?

  - by claws

  Hello, I'm reading "Understanding Linux Kernel". This is the snippet that explains how Linux uses Segmentation which I didn't understand. Segmentation has been included in 80 x 86 microprocessors to encourage programmers to split their applications into logically related entities, such as subroutines or global and local data areas. However, Linux uses segmentation in a very limited way. In fact, segmentation and paging are somewhat redundant, because both can be used to separate the physical address spaces of processes: segmentation can assign a different linear address space to each process, while paging can map the same linear address space into different physical address spaces. Linux prefers paging to segmentation for the following reasons: Memory management is simpler when all processes use the same segment register values that is, when they share the same set of linear addresses. One of the design objectives of Linux is portability to a wide range of architectures; RISC architectures in particular have limited support for segmentation. All Linux processes running in User Mode use the same pair of segments to address instructions and data. These segments are called user code segment and user data segment , respectively. Similarly, all Linux processes running in Kernel Mode use the same pair of segments to address instructions and data: they are called kernel code segment and kernel data segment , respectively. Table 2-3 shows the values of the Segment Descriptor fields for these four crucial segments. I'm unable to understand 1st and last paragraph.

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• Finding the right terminology for a dictionary table

  - by Karl Forner

  My concern is about what I currently call "dictionary tables", that are database tables containing a list of controlled vocabulary. Let's use an example: Suppose you have a table User containing fields: user_id : primary key first_name last_name user_type_id : foreign key to the UserType table and another table UserType with just two fields: user_type_id : primary key name : the name/value of a particular type of user. For instance, the UserType table may contain (1, Administrator), (2, PowerUser), (3, Normal)... My question is: what is the canonical term for a table like UserType, that only contains a list of (dictinct) words. I want to publish some code that help managing this kind of tables, but first I have to name them ! Thanks for your help. Current state of thought: For now I feel Lookup Tables is a good term. It is also used with the same meaning in these posts: http://dbix-class.35028.n2.nabble.com/RFC-Component-for-Lookup-tables-td3504085.html http://tonyandrews.blogspot.de/2004/10/otlt-and-eav-two-big-design-mistakes.html Lookup Tables Best Practices: DB Tables... or Enumerations The only problem is that lookup table is also sometimes used to name a junction table.

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• Winsock WSAAsyncSelect sending without an infinite buffer

  - by Xexr

  Hi, This is more of a design question than a specific code question, I'm sure I am missing the obvious, I just need another set of eyes. I am writing a multi-client server based on WSAAsyncSelect, each connection is made into an object of a connection class I have written which contains associated settings and buffers etc. My question concerns FD_WRITE, I understand how it operates: One FD_WRITE is sent immediately after a connection is established. Thereafter, you should send until WSAEWOULDBLOCK is received at which point you store what is left to send in a buffer, and wait to be told that it is ok to send again. This is where I have a problem, how large do I make this holding buffer within each connections object? The amount of time until a new FD_WRITE is received is unknown, I could be attempting to send a lot of stuff during this period, all the time adding to my outgoing buffer. If I make the buffer dynamic, memory usage could spiral out of control if for whatever reason, I am unable to send() and reduce the buffer. So my question is how do you generally handle this situation? Note I am not talking about the network buffer itself which winsock uses, but one of my own creation used to "queue" up sends. Hope I explained that well enough, thanks all!

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• retrieving object information with Doctrine

  - by ajsie

  i want to fetch information from the database using objects. i really like this approach cause this is more OOP: $user = Doctrine_Core::getTable('User')->find(1); echo $user->Email['address']; echo $user->Phonenumbers[0]->phonenumber; rather than: $q = Doctrine_Query::create() ->from('User u') ->leftJoin('u.Email e') ->leftJoin('u.Phonenumbers p') ->where('u.id = ?', 1); $user = $q->fetchOne(); echo $user->Email['address']; echo $user->Phonenumbers[0]['phonenumber']; the problem is that the first one uses 3 queries (3 different tables), while the second one uses only 1 (and is therefore recommended technique). but i feel that it destroys the object oriented design. cause ORM is meant to give us an OOP approach so that we could focus on objects and not the relational database. but now they want us to go back to use SQL like pattern. there isn't a way to get information form multiple tables not using DQL? the above examples are taken from the documentation: doctrine

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