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• Confusion about inheritance

  - by Samuel Adam

  I know I might get downvoted for this, but I'm really curious. I was taught that inheritance is a very powerful polymorphism tool, but I can't seem to use it well in real cases. So far, I can only use inheritance when the base class is an abstract class. Examples : If we're talking about Product and Inventory, I quickly assumed that a Product is an Inventory because a Product must be inventorized as well. But a problem occured when user wanted to sell their Inventory item. It just doesn't seem to be right to change an Inventory object to it's subtype (Product), it's almost like trying to convert a parent to it's child. Another case is Customer and Member. It is logical (at least for me) to think that a Member is a Customer with some more privileges. Same problem occurred when user wanted to upgrade an existing Customer to become a Member. A very trivial case is the Employee case. Where Manager, Clerk, etc can be derived from Employee. Still, the same upgrading issue. I tried to use composition instead for some cases, but I really wanted to know if I'm missing something for inheritance solution here. My composition solution for those cases : Create a reference of Inventory inside a Product. Here I'm making an assumption about that Product and Inventory is talking in a different context. While Product is in the context of sales (price, volume, discount, etc), Inventory is in the context of physical management (stock, movement, etc). Make a reference of Membership instead inside Customer class instead of previous inheritance solution. Therefor upgrading a Customer is only about instantiating the Customer's Membership property. This example is keep being taught in basic programming classes, but I think it's more proper to have those Manager, Clerk, etc derived from an abstract Role class and make it a property in Employee. I found it difficult to find an example of a concrete class deriving from another concrete class. Is there any inheritance solution in which I can solve those cases? Being new in this OOP thing, I really really need a guidance. Thanks!

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• Why enumerator structs are a really bad idea (redux)

  - by Simon Cooper

  My previous blog post went into some detail as to why calling MoveNext on a BCL generic collection enumerator didn't quite do what you thought it would. This post covers the Reset method. To recap, here's the simple wrapper around a linked list enumerator struct from my previous post (minus the readonly on the enumerator variable): sealed class EnumeratorWrapper : IEnumerator<int> { private LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } If you have a look at the Reset method, you'll notice I'm having to cast to IEnumerator to be able to call Reset on m_Enumerator. This is because the implementation of LinkedList<int>.Enumerator.Reset, and indeed of all the other Reset methods on the BCL generic collection enumerators, is an explicit interface implementation. However, IEnumerator is a reference type. LinkedList<int>.Enumerator is a value type. That means, in order to call the reset method at all, the enumerator has to be boxed. And the IL confirms this: .method public hidebysig newslot virtual final instance void Reset() cil managed { .maxstack 8 L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> EnumeratorWrapper::m_Enumerator L_0007: box [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> L_000c: callvirt instance void [mscorlib]System.Collections.IEnumerator::Reset() L_0011: nop L_0012: ret } On line 0007, we're doing a box operation, which copies the enumerator to a reference object on the heap, then on line 000c calling Reset on this boxed object. So m_Enumerator in the wrapper class is not modified by the call the Reset. And this is the only way to call the Reset method on this variable (without using reflection). Therefore, the only way that the collection enumerator struct can be used safely is to store them as a boxed IEnumerator<T>, and not use them as value types at all.

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• C++ and SDL resource management for 2D game

  - by KuruptedMagi

  My first question is about stateManagers. I do not use the singleton pattern (read many random posts with various reasons not to use it), I have gameStateManager which runs the pointer cCurrentGameState-render(), etc. I want to make a transitioning game, this engine should ideally cover both a platformer and a bird's eye RPG (with some recoding, I just mean the base engine), both of which will load different levels and events, such as world map, dungeon, shops, etc. So I then thought, rather then having to store all this data within all the states, I would break the engine into gameStates, and playStates... when gameState reaches gameStatePlay(), gameStatePlay simply runs the usual handleInput, logic, and render for the playStates, just as the low level gameStateManager does. This lets me store all the player data within the base playstate class without storing useless data in the gameStates. Now I have added a seperate mapEditor, which uses editorStates from gameStateEditor. Is this too much usage of the gameState concept? It seems to work pretty well for me, so I was wondering if I am too far off a common implementation of this. My second question is on image resources. I have my sprite class with nothing but static members, mainly loadImage, applySurface, and my screen pointer. I also have a map pairing imageName enums with actual SDL_Surface pointers, and one pairing clipNumber enums with a wrapper class for a vector of clips, so that each reference in the map can have different amounts of clips with different sizes. I thought it would be better to store all these images, and screen within one static body, since 20 different goblins all use the same sprite sheet, and all need to print to the same screen, and of course, this way I do not need to pass my screen reference to every little entity. The imageMap seems to work very well, I can even add the ability to search through the map at creation of entity type to see if a particular image at creation, creating if it doesnt exist, and destroying the image if the last entity that needs it was just destroyed. The vectored clip map however, seems to take too long to initialize, so if i run past the state that initializes them to fast, the game crashes <. Plus, the clip map call is half of this line =P SPRITE::applySurface( cEditorMap.cTiles[x][y].iX, cEditorMap.cTiles[x][y].iY, SPRITE::mImages[ IMAGE_TILEMAP ], SPRITE::screen, SPRITE::mImageClips[IMAGE_TILEMAP]->clips.at( cEditorMap.cTiles[x][y].iTileType ) ); Again, do I have the right idea? I like the imageMap, but am I better off with each entity storing its own clips? My last question is about collision detection. I only grasp the basics, will look at per-pixel and circular soon, but how can I determine which side the collision comes from with just the basic square collision detection, I tried breaking each entity into 4 collision zones, but that just gave me problems with walking through walls and the like <. Also, is per-pixel color collision a good way to decide what collision just occured, or is checking multiple colors for multiple entities too taxing each cycle?

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• Content API for Shopping Office Hours - June 12, 2012

  Content API for Shopping Office Hours - June 12, 2012 Hangout discussing Product Listing Ads (PLAs) and the Google Affiliate Network (GAN) with guest Mark Coppin (GAN) and Claire Hugo (PLAs) of Google. In the Hangout, we reference the video "How to create a new Product Listing Ads campaign" (www.youtube.com which can be found in the Getting Starting page on the Shopping/Ads integration site (www.google.com Also, check out the GAN site to learn more: www.google.com From: GoogleDevelopers Views: 703 6 ratings Time: 31:23 More in Science & Technology

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• Behavior Trees and Animations

  - by Tom

  I have started working on the AI for a game, but am confused how I should handle animations. I will be using a Behavior Tree for AI behavior and Cocos2D for my game engine. Should my "PlayAnimationWalk" just be another node in the tree? Something similar to this: [Approach Player] - Play Walk animation - Move Towards player - Stop Walk animation Or should the node just update an AnimationState in the blackboard and have some type of animation handler/component reference this for which animation should be playing? This has been driving me nuts :)

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• Why should I not do a masters degree

  - by aurel

  I have left university on July 2010 where I studied web design (as we all know you learn more by your self but that’s not the issue at the moment). Since then I have not managed to find a job (apart from a one month work experience), from the way things are going, and by taking into account the fact that all my university friends are in the same situation, I don’t think that I am going to find a job soon (within the industry) Now as we all do, even though I don’t have a job, I am still working on personal projects and try to keep up to date (I don’t need a job or uni to do this) – but I am thinking, because there is not work available, would it be worth going back to uni for a master degree? I know I don’t need it and I know that is unlikely that I will learn anything important, as I believe in self learning, and in most cases it is a lot more effective (but I have to say I don’t mind going back to school) The only reason I am thinking of doing the master is, (and this is where I need your help): If it takes me a year to get a job, then on the interview, would the employer think “what the hell did this guy do since he left university” – now if I go to university that would solve this problem. Or I’m I making up a problem that does not exist Plus, I know that employers need examples of sites that I have been working on, at the moment I only have 3 (as when working on personal projects, where their is not time limit I tend drag things in order to get them perfect, and they never get perfect) – so by going back to uni, then this problem maybe solved I said all this as I have read a lot about the fact that you don’t need to have a masters degree to work on web design market (and I totally agree) but considering my concern, the question is should I do a masters course to avoid just spending hours in my room working and learning in my own (but that it would be hard to convince employers that I was really learning in my room) Maybe because I’m still young age 22 not that old anyway :), but I don’t have the “dream” of being rich, so if I were to tell the truth I don’t really care of the fact that I don’t have a job (at the moment), because regardless, I am working on what I love every day, but I know that in the future when I will need the job I may find it harder to get one, if I neglect doing so now Every time I ask a question that I’m not sure about, I keep going on and on, but I really hope you get what I am trying to get across. By the way the course that I am looking at for a masters says that it would teach me how to do these: e-commerce e-government e-science e-learning I don’t know any of them, a part from e-commerce Thanks

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• See you at OSCON!

  - by darcy

  In just under a month, I'll be speaking at the OSCON Java conference about various OpenJDK and JDK 7 matters: JDK 7 in a Nutshell The State of JDK and OpenJDK More detailed talks on those topics include Stuart's session on Coin in Action: Using New Java SE 7 Language Features in Real Code and Dalibor's OpenJDK – When And How To Contribute To The Java SE Reference Implementation. See you in Portland!

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• Open Source PHP based secure file download script?

  - by SiddharthP

  Basically I need a self hosted solution where I as the admin can create client areas (which can be simple folders) where I upload files and secure them with username / pass. A client page will then be automatically generated which the client can access the username / pass and download the files. It's relatively simple script but i'm having a hard time finding open source solutions which accomplish what i need. Any help would be appreciated.

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• Beginner C# image loading woes - NullReferenceException

  - by Seth Taddiken

  I keep getting a "NullReferenceExeption was unhandled" with "Object reference not set to an instance of an object." written under it. I have all of the images (png) correct with names and added to references. protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); backGround = Content.Load<Texture2D>("Cracked"); player1.playerBlock = Content.Load<Texture2D>("square"); player2.playerBlock = Content.Load<Texture2D>("square2"); }

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• New Book: "Systems Performance: Enterprise and the Cloud"

  - by uwes

  Brendan Gregg, former Solaris kernel engineer at Sun published his new book "Systems Performance: Enterprise and the Cloud" in October. The book is a modern, very comprehensive guide to general system performance principles and practices, as well as a highly detailed reference for specific UNIX and Linux observability tools used to examine and diagnose operating system behaviour. Read a more detailed abstract and review on Harry J Foxwell's Blog entry "Brendan Gregg's "Systems Performance: Enterprise and the Cloud"

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• Our Favorite Highlights from OpenWorld 2012

  - by Kathy.Miedema

  By Kathy Miedema and Misha Vaughan, Oracle Applications User Experience The Oracle Applications User Experience (UX) team’s activities around OpenWorld expand every year, but this year we certainly raised the bar.   Members of our team helped deliver three, separate, all-day training events in the week prior to OpenWorld. Our Fusion User Experience Advocates (FXA) and Applications UX Sales Ambassadors (SAMBA) have all-new material around the Oracle user experience to deliver at conferences in the coming year - Fusion Applications design patterns, mobile design patterns, and the new face of Fusion. We also delivered a hands-on workshop sharing user experience tools for our customers that is designed to answer this question: "If I have no UX staff, what do I do?" We also spent the weeks just before OpenWorld preparing to talk about the new face of Fusion Applications, a greatly simplified entry experience into Fusion Applications for self-service users, CRM users, and IT managers who want to change the look and feel quickly. Special thanks to Oracle ACE Director Floyd Teter for the first mention of our project.Jeremy Ashley, VP, Oracle Applications User Experience Customers may have seen one of the many OpenWorld session demos of the new face of Fusion, which will be available with Fusion Applications soon. It was shown in sessions by Oracle's Chris Leone, Anthony Lye, and our own Vice President, Jeremy Ashley, among others.   Leone reinforced the importance of user experience as one of three main design principles for Fusion Applications, emphasizing that Fusion was designed from the beginning to be intelligent, social, and mobile. User experience highlights of the new face of Fusion, he said, included the need for "zero training," and he called the experience "easy to use." He added that deploying it for HCM self-service would be effortless.  Customers take part in a usability lab tour during OpenWorld 2012. Customers also may have seen the new face of Fusion on the demogrounds or during one of our teams' chartered lab tours at the end of the week. We tested other new designs at our on-site lab in the Intercontinental Hotel, next to Moscone West. Applications User Experience team members show eye-tracking and mobile demos at OOW. We were also excited to kick off new branches of the Oracle Usability Advisory Board, which now has groups in Latin America and the Middle East, in addition to North America and EMEA.   And we were pleasantly surprised by the interest in one of our latest research projects, Oracle Voice, which is designed to enable faster data input for on-the-go users. We offer a big thank-you to the Nuance demopod for sharing the demo with OpenWorld attendees.  For more information on our program and products like the new face of Fusion, please comment below. 

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• What is a good strategy for binding view objects to model objects in C++?

  - by B.J.

  Imagine I have a rich data model that is represented by a hierarchy of objects. I also have a view hierarchy with views that can extract required data from model objects and display the data (and allow the user to manipulate the data). Actually, there could be multiple view hierarchies that can represent and manipulate the model (e.g. an overview-detail view and a direct manipulation view). My current approach for this is for the controller layer to store a reference to the underlying model object in the View object. The view object can then get the current data from the model for display, and can send the model object messages to update the data. View objects are effectively observers of the model objects and the model objects broadcast notifications when properties change. This approach allows all the views to update simultaneously when any view changes the model. Implemented carefully, this all works. However, it does require a lot of work to ensure that no view or model objects hold any stale references to model objects. The user can delete model objects or sub-hierarchies of the model at any time. Ensuring that all the view objects that hold references to the model objects that have been deleted is time-consuming and difficult. It feels like the approach I have been taking is not especially clean; while I don't want to have to have explicit code in the controller layer for mediating the communication between the views and the model, it seems like there must be a better (implicit) approach for establishing bindings between the view and the model and between related model objects. In particular, I am looking for an approach (in C++) that understands two key points: There is a many to one relationship between view and model objects If the underlying model object is destroyed, all the dependent view objects must be cleaned up so that no stale references exist While shared_ptr and weak_ptr can be used to manage the lifetimes of the underlying model objects and allows for weak references from the view to the model, they don't provide for notification of the destruction of the underlying object (they do in the sense that the use of a stale weak_ptr allows for notification), but I need an approach that notifies the dependent objects that their weak reference is going away. Can anyone suggest a good strategy to manage this?

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• java webservice requires usernametoken over basichttpbinding (3 replies)

  I need to call a Java webservice. I can add a service reference without problems, and I get Intellisense in Visual Studio. However, when I try to call a service method I get an error message saying &quot;Missing (user) Security Information&quot;. I n my code I try to set usercredentials: testWS.WarrantyClaimServiceClient svc new TestClient.testWS.WarrantyClaimServiceClient(); svc.ClientCredentials.UserName....

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• EBS Concurrent Processing Information Center

  - by LuciaC

  Do you have problems or questions about concurrent request processing?  Do you want to know: How and when to run CP Diagnostics? What are the latest Hot Topics being looked at for Concurrent Processing? All about the Concurrent Process Analyzer self-service Health-Check script? Go to the EBS Concurrent Processing Information Center (Doc ID 1304305.1) and find out the above and lots more!

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• Should comments say WHY the program is doing what it is doing? (opinion on a dictum by the inventor of Forth)

  - by AKE

  The often provocative Chuck Moore (inventor of the Forth language) gave the following advice (paraphrasing): "Use comments sparingly. Programs are self-documenting, with a modicum of help from mnemonics. Comments should say WHAT the program is doing, not HOW." My question: Should comments say WHY the program is doing what it is doing? Update: In addition to the answers below, these two provide additional insight. Beginner's guide to writing comments? http://programmers.stackexchange.com/a/98609/62203

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• How to Create a Group on Facebook

  Possessing a facebook group is 1 of the finest techniques to advertise your self (or business) as a leader or as somebody of importance. They are in addition basic to produce. I am going to aid you g... [Author: Damien Willis - Computers and Internet - June 17, 2010]

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• Should one comment differently in functional languages

  - by Tom Squires

  I'm just getting started with functional programming and I'm wondering the correct way to comment my code. It seems a little redundant to comment a short function as the names and signature already should tell you everything you need to know. Commenting larger functions also seems a little redundant since they are generally comprised of smaller self-descriptive functions. What is the correct way to comment a functional program? Should I use the same approach as in iterative programming?

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• Modélisation réseau, un article de Philippe Latu sur la modélisation en couche des protocoles réseau

  La modélisation du fonctionnement des réseaux électroniques de communications a toujours fait l'objet de grandes luttes d'influence entre les organismes de normalisation, les compagnies de télécommunications et les constructeurs. Avec l'avènement de l'Internet, un modèle contemporain faisant la synthèse entre les modèles de référence historiques OSI et TCP/IP s'est imposé. L'objectif de cet article est d'introduire les concepts de modélisation, de présenter les deux modélisations dominantes et le...

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• CRM: New Rollup Patches Released

  - by LuciaC

  See the table below for new rollup patches released for CRM family products. Product  Patch Number Reference Service Patch 17467506:R12.CS.B12.1.3:BUG FIXES FOR CS: OCTOBER'13 RUP PATCH n/a iStore Patch 16509570:R12.IBE.B- ORACLE ISTORE 12.1.3+ ROLLUP 1 Doc ID 1560963.1 Lease and Finance Management Patch 17485497:R12.OKL.B - OLFM : 1213 RUP3 DELTA 15 n/a For Trade Management and Price Protection the following Information Centers list the latest recommended patches and recently released patches: Critical, Recommended and Latest Patches for Oracle Trade Management (Doc ID 1569791.2) Critical, Recommended and Latest Patches for Oracle Price Protection (Doc ID 1305110.2)

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• SQLAuthority News Microsoft SQL Server Protocol Documentation Download

  The Microsoft SQL Server protocol documentation provides detailed technical specifications for Microsoft proprietary protocols (including extensions to industry-standard or other published protocols) that are implemented and used in Microsoft SQL Server to interoperate or communicate with Microsoft products.The documentation includes a set of companion overview and reference documents that supplement [...]...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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• NUnit SetUp and TearDown

  - by Lijo

  I have some experience in MS Test but new to NUnit. Whether NUnit [Setup] is corresponding to [ClassInitialize] or [TestInitialize] in MS Test? What is the NUnit attribute corresponding to [TestInitialize]? REFERENCE: http://stackoverflow.com/questions/1873191/testinitialize-gets-fired-for-every-test-in-my-visual-studio-unit-tests http://stackoverflow.com/questions/4602288/nunit-testcontext-currentcontext-test-not-working

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• build my own CDN service

  - by user5332

  I have two servers, both with self domain 1st www.myexample1.com 2nd www.myexample2.com and now I would like to setup CDN of www.myexample1.com to www.myexample2.com but I dont know how setup DNS or Apache that, so both servers served files for www.myexample1.com request ... I don't need solve databases, sessions or someting else... but I need know, how to do that both server will available as www.myexample1.com

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• The dirt locker: Dirty duty on the front lines of IT

  <b>InfoWorld:</b> "Wanted: Sys admin to log long hours and plan vacations around other people's paydays. Must be willing to put up with self-absorbed IT professionals. Ability to sniff out fraud essential."

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• Any technical references for game-oriented icons and symbols?

  - by willc2

  To make localizing easier, I'm using icons to show in-game information like achievements and bonuses. Coming up with good designs isn't easy, especially when it has to be integrated into the rest of the game's art style. Can I do better than looking at some random selection of existing games? Are there any reference books or sites that cover game graphics specifically? I'm looking for more theory and best-practices rather than pre-made graphics.

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• Traditional POS is Dead

  - by David Dorf

  Traditional POS is dead -- I've heard that one before. Here's an excerpt from Joe Skorupa's blog over at RIS where he relayed ten trends that were presented at NRF. 7. Mobile POS signals death of traditional POS. Shoppers don't love self-checkout, but they prefer it to long queues or dealing with associates. Fixed POS is expensive and bulky. Mobile POS frees floor space for other purposes and converts associates from being cashiers to being sales assistants that provide new levels of customer service and incremental basket sales. In addition to unplugging the POS, new alternatives are starting to take hold - thin client, POS as a service, and replacing POS software with e-commerce platforms. I'll grant that in some situations for some retailers there might be an opportunity to to ditch the traditional POS, but for the majority of retailers that's just not practical. Take it from a guy that had to wake up at 3am after every Thanksgiving to monitor POS systems across the US on Black Friday. If a retailer's website goes down on Black Friday, they will take a significant hit. If a retailer's chain-wide POS system goes down on Black Friday, that retailer will cease to exist. Mobile POS works great for Apple because the majority of purchases are one or two big-ticket items that don't involve cash. There's still a traditional POS in every store to fall back on (its just hidden). Try this at home: Choose your favorite e-commerce site and add an item to the cart while timing how long it takes. Now multiply that by 15 to represent the 15 items you might buy at store like Target. The user interface isn't optimized for bulk purchases, and that's how it should be. The webstore and POS are designed for different purposes. Self-checkout is a great addition to POS and so is mobile checkout. But they add capabilities to POS, not replace it. Centralized architectures, even those based in the cloud, are quite viable as long as there's resiliency in the registers. You cannot assume perfect access to the network, so a POS must always be able to sell regardless of connectivity. Clearly the different selling channels should be sharing common functionality. Things like calculating tax, accepting coupons, and processing electronic payments can be shared, usually through a service-oriented architecture. This lowers costs and providers greater consistency, both of which help retailers. On paper these technologies look really good and we should continue to push boundaries, but I'm not ready to call the patient dead just yet.

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