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• What is the diffference between "data hiding" and "encapsulation"?

  - by john smith optional

  I'm reading "Java concurrency in practice" and there is said: "Fortunately, the same object-oriented techniques that help you write well-organized, maintainable classes - such as encapsulation and data hiding -can also help you crate thread-safe classes." The problem #1 - I never heard about data hiding and don't know what it is. The problem #2 - I always thought that encapsulation is using private vs public, and is actually the data hiding. Can you please explain what data hiding is and how it differs from encapsulation?

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• DDD and Value Objects. Are mutable Value Objects a good candidate for Non Aggr. Root Entity?

  - by Tony

  Here is a little problem Have an entity, with a value object. Not a problem. I replace a value object for a new one, then nhibernate inserts the new value and orphan the old one, then deletes it. Ok, that's a problem. Insured is my entity in my domain. He has a collection of Addresses (value objects). One of the addresses is the MailingAddress. When we want to update the mailing address, let's say zipcode was wrong, following Mr. Evans doctrine, we must replace the old object for a new one since it's immutable (a value object right?). But we don't want to delete the row thou, because that address's PK is a FK in a MailingHistory table. So, following Mr. Evans doctrine, we are pretty much screwed here. Unless i make my addressses Entities, so i don't have to "replace" it, and simply update its zipcode member, like the old good days. What would you suggest me in this case? The way i see it, ValueObjects are only useful when you want to encapsulate a group of database table's columns (component in nhibernate). Everything that has a persistence id in the database, is better off to make it an Entity (not necessarily an aggregate root) so you can update its members without recreating the whole object graph, specially if that's a deep-nested object. Do you concur? Is it allowed by Mr. Evans to have a mutable value object? Or is a mutable value object a candidate for an Entity? Thanks

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• MVP Pattern Philsophical Question - Security Checking in UI

  - by Brian

  Hello, I have a philosophical question about the MVP pattern: I have a component that checks whether a user has access to a certain privilege. This privilege turns on or off certain UI features. For instance, suppose you have a UI grid, and for each row that gets bound, I do a security check to see if certain features in the grid should be enabled or disabled. There are two ways to do this: have the UI/view call the component's method, determine if it has access, and enable/disable or show/hide. The other is have the view fire an event to the presenter, have the presenter do the check and return the access back down to the view through the model or through the event arg. As per the MVP pattern, which component should security checks fit into, the presenter or the view? Since the view is using it to determine its accessibility, it seems more fitting in the view, but it is doing database checks and all inside this business component, and there is business logic there, so I can see the reverse argument too. Thoughts? Thanks.

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• Object behaviour or separate class?

  - by Andrew Stephens

  When it comes to OO database access you see two common approaches - the first is to provide a class (say "Customer") with methods such as Retrieve(), Update(), Delete(), etc. The other is to keep the Customer class fairly lightweight (essentially just properties) and perform the database access elsewhere, e.g. using a repository. This choice of approaches doesn't just apply to database access, it can crop up in many different OOD scenarios. So I was wondering if one way is preferable over the other (although I suspect the answer will be "it depends")! Another dev on our team argues that to be truly OO the class should be "self-contained", i.e. providing all the methods necessary to manipulate and interact with that object. I personally prefer the repository approach - I don't like bloating the Customer class with all that functionality, and I feel it results in cleaner code having it elsewhere, but I can't help thinking I'm seriously violating core OO concepts! And what about memory implications? If I retrieve thousands of Customer objects I'm assuming those with the data access methods will take up a lot more memory than the property-only objects?

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• Switch vs Polymorphism when dealing with model and view

  - by Raphael Oliveira

  I can't figure out a better solution to my problem. I have a view controller that presents a list of elements. Those elements are models that can be an instance of B, C, D, etc and inherit from A. So in that view controller, each item should go to a different screen of the application and pass some data when the user select one of them. The two alternatives that comes to my mind are (please ignore the syntax, it is not a specific language) 1) switch (I know that sucks) //inside the view controller void onClickItem(int index) { A a = items.get(index); switch(a.type) { case b: B b = (B)a; go to screen X; x.v1 = b.v1; // fill X with b data x.v2 = b.v2; case c: go to screen Y; etc... } } 2) polymorphism //inside the view controller void onClickItem(int index) { A a = items.get(index); Screen s = new (a.getDestinationScreen()); //ignore the syntax s.v1 = a.v1; // fill s with information about A s.v2 = a.v2; show(s); } //inside B Class getDestinationScreen(void) { return Class(X); } //inside C Class getDestinationScreen(void) { return Class(Y); } My problem with solution 2 is that since B, C, D, etc are models, they shouldn't know about view related stuff. Or should they in that case?

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• Bachelor in Game Development [on hold]

  - by vandamon taigi

  At this moment, I'm in year 11 in Romania. I have started thinking about an university to go to and I am not really sure which should be my choice. I want it to be game development, but I also want it to be good and fun university.Thing is, I don't want to pay 30 grands a year or so for Cambridge or something like that. I am looking for a decent university at a decent price. I have in my hometown a University that is ranked 1613 world-wide which has a software development category. I need some advices and some possible options for decent universities ( Personal experience is greatly appreciated )

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• Merge two different API calls into One

  - by dhilipsiva

  I have two different apps in my django project. One is "comment" and an other one is "files". A comment might save some file attached to it. The current way of creating a comment with attachments is by making two API calls. First one creates an actual comment and replies with the comment ID which serves as foreign key for the Files. Then for each file, a new request is made with the comment ID. Please note that file is a generic app, that can be used with other apps too. What is the cleanest way of making this into one API call? I want to have this as a single API call because I am in a situation where I need to send user an email with all the files as attachment when a comment is made. I know Queueing is the ideal way to do it. But I don't have the liberty to add queing to our stack now. So this was the only way I could think of.

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• Starting point for a simple game written in action script [closed]

  - by Hossein

  Possible Duplicate: AS3/Flash Game Dev: Looking for good & current step by step. Hi, I want to develop a simple game like: http://www.albinoblacksheep.com/games/falldown2 And then making it a bit more fancy. But I don't know where to start. I have already started AS3 so I know about the syntax and stuff, but I am kinda lost. Does anyone knows of a nice starting point or a tutorial that can help me with this? Thanks

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• Server-side Architecture for Online Game

  - by Draiken

  Hi, basically I have a game client that has communicate with a server for almost every action it takes, the game is in Java (using LWJGL) and right now I will start making the server. The base of the game is normally one client communicating with the server alone, but I will require later on for several clients to work together for some functionalities. I've already read how authentication server should be sepparated and I intend on doing it. The problem is I am completely inexperienced in this kind of server-side programming, all I've ever programmed were JSF web applications. I imagine I'll do socket connections for pretty much every game communication since HTML is very slow, but I still don't really know where to start on my server. I would appreciate reading material or guidelines on where to start, what architecture should the game server have and maybe some suggestions on frameworks that could help me getting the client-server communication. I've looked into JNAG but I have no experience with this kind of thing, so I can't really tell if it is a solid and good messaging layer. Any help is appreciated... Thanks !

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• Calculating the "power" of a player in a "Defend Your Castle" type game

  - by Jesse Emond

  I'm a making a "Defend Your Castle" type game, where each player has a castle and must send units to destroy the opponent's castle. It looks like this (and yeah, this is the actual game, not a quick paint drawing..): Now, I'm trying to implement the AI of the opponent, and I'd like to create 4 different AI levels: Easy, Normal, Hard and Hardcore. I've never made any "serious" AI before and I'd like to create a quite complete one this time. My idea is to calculate a player's "power" score, based on the current health of its castle and the individual "power" score of its units. Then, the AI would just try to keep a score close to the player's one(Easy would stay below it, Normal would stay near it and Hard would try to get above it). But I just don't know how to calculate a player's power score. There are just too many variables to take into account and I don't know how to properly use them to create one significant number(the power level). Could anyone help me out on this one? Here are the variables that should influence a player's power score: Current castle health, the unit's total health, damage, speed and attack range. Also, the player can have increased Income(the money bag), damage(the + Damage) and speed(the + speed)... How could I include them in the score? I'm really stuck here... Or is there an other way that I could implement AI for this type of game? Thanks for your precious time.

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• Preffered lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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• Questioning the motivation for dependency injection: Why is creating an object graph hard?

  - by oberlies

  Dependency injection frameworks like Google Guice give the following motivation for their usage (source): To construct an object, you first build its dependencies. But to build each dependency, you need its dependencies, and so on. So when you build an object, you really need to build an object graph. Building object graphs by hand is labour intensive (...) and makes testing difficult. But I don't buy this argument: Even without dependency injection, I can write classes which are both easy to instantiate and convenient to test. E.g. the example from the Guice motivation page could be rewritten in the following way: class BillingService { private final CreditCardProcessor processor; private final TransactionLog transactionLog; // constructor for tests, taking all collaborators as parameters BillingService(CreditCardProcessor processor, TransactionLog transactionLog) { this.processor = processor; this.transactionLog = transactionLog; } // constructor for production, calling the (productive) constructors of the collaborators public BillingService() { this(new PaypalCreditCardProcessor(), new DatabaseTransactionLog()); } public Receipt chargeOrder(PizzaOrder order, CreditCard creditCard) { ... } } So dependency injection may really be an advantage in advanced use cases, but I don't need it for easy construction and testability, do I?

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• how to write high quality GUI software with qt?

  - by Opetmar

  I want to write a project using QT library, so after learning the library and mastering it how should I start, what other libraries or things that I should learn? are there any other tools that will help me during the development or tools well help the end user to install the software and using it? What are the things that I should be aware? what are the things that I should avoid so it can run efficiently?

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• Publish/Subscribe/Request for exchange of big, complex, and confidential data?

  - by Morten

  I am working on a project where a website needs to exchange complex and confidential (and thus encrypted) data with other systems. The data includes personal information, technical drawings, public documents etc. We would prefer to avoid the Request-Reply pattern to the dependent systems (and there are a LOT of them), as that would create an awful lot of empty traffic. On the other hand, I am not sure that a pure Publisher/Subscriber pattern would be apropriate -- mainly because of the complex and bulky nature of the data to be exchanged. For that reason we have discussed the possibility of a "publish/subscribe/request" solution. The Publish/Subscribe part would be to publish a message to the dependent systems, that something is ready for pickup. The actual content is then picked up by old-school Request-Reply action. How does this sound to you?? Regards, Morten

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• How to "translate" interdependent object states in code?

  - by Earl Grey

  I have the following problem. My UI interace contains several buttons, labels, and other visual information. I am able to describe every possible workflow scenario that should be be allowed on that UI. That means I can describe it like this - when button A is pressed, the following should follow - In the case of that A button, there are three independent factors that influence the possible result when pushing the A button. The state of the session (blank, single, multi, multi special), the actual work that is being done by the system at the moment of pressing the A button (nothing was happening, work was being done, work was paused) and a separate UI element that has two states (on , off)..This gives me a 3 dimensional cube with 24 possible outcomes. I could write code for this using if cycles, switch cycles etc....but the problem is, I have another 7 buttons on that ui, I can enter this UI from different states..some buttons change the state, some change parameters... To sum up, the combinations are mindbogling and I am not able come up with a methodology that scales and is systematically reliable. I am able to describe EVERY workflow with words, I am sure my description is complete and without logical errors. But I am not able to translate that into code. I was trying to draw flowcharts but it soon became visually too complicated due to too many if "emafors". Can you advice how to proceeed?

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• Building a distributed system on Amazon Web Services

  - by Songo

  Would simply using AWS to build an application make this application a distributed system? For example if someone uses RDS for the database server, EC2 for the application itself and S3 for hosting user uploaded media, does that make it a distributed system? If not, then what should it be called and what is this application lacking for it to be distributed? Update Here is my take on the application to clarify my approach to building the system: The application I'm building is a social game for Facebook. I developed the application locally on a LAMP stack using Symfony2. For production I used an a single EC2 Micro instance for hosting the app itself, RDS for hosting my database, S3 for the user uploaded files and CloudFront for hosting static content. I know this may sound like a naive approach, so don't be shy to express your ideas.

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• Avoiding the Anaemic Domain - How to decide what single responsibility a class has

  - by thecapsaicinkid

  Even after reading a bunch I'm still falling into the same trap. I have a class, usually an enity. I need to implement more than one, similar operations on this type. It feels wrong to (seemingly arbitrarily) choose one of these operations to belong inside the entity and push the others out to a separate class; I end up pushing all operations to service classes and am left with an anaemic domain. As a crude example, imagine the typical Employee class with numeric properties to hold how many paid days the employee is entitled to for both sickness and holiday and a collection of days taken for each. public class Employee { public int PaidHolidayAllowance { get; set; } public int PaidSicknessAllowance { get; set; } public IEnumerable<Holiday> Holidays { get; set; } public IEnumerable<SickDays> SickDays { get; set; } } I want two operations, one to calculate remaining holiday, another for remaining paid sick days. It seems strange to include say, CalculateRemaingHoliday() in the Employee class and bump CalculateRemainingPaidSick() to some PaidSicknessCalculator class. I would end up with a PaidSicknessCalculator and a RemainingHolidayCalculator and the anaemic Employee entity as seen above. The other alternative would be to put both operations in the Employee class and kick Single Responsibility to the curb. That doesn't make for particularly maintainable code. I suppose the Employee class should have some initialisation/validation logic (not accepting negative alowances etc.) So maybe I just stick to basic initialisation and validation in the entities themselves and be happy with my separate calculator classes. Or maybe I should be asking myself if Anaemic Domain is actually causing me some tangible problems with my code.

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• Is extensive documentation a code smell?

  - by Griffin

  Every library, open-source project, and SDK/API I've ever come across has come packaged with a (usually large) documentation file, and this seems contradictory to the wide-spread belief that good code needs little to no comments. What separates documentation from this programming methodology? a one to two page overview of a package seems reasonable, but elegant code combined with standard intelisense should have theoretically deprecated the practice of documentation by now IMO. I feel like companies only create detailed documentation and tutorials because its what they've always done. Why should developers have to constantly be searching through online documentation in order to learn how to do things when such information should be intrinsic to the classes, methods and namespaces?

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• How to approach big developer companies if I have a killer game idea? (for mobile devices)

  - by Balázs Dávid

  I have an idea for a game that has a potential, but I'm not a programmer. How to tell this to development companies without being my idea stolen? All I want from the company is first to watch a 3-minute long video presentation about my idea and if they see fantasy in it then we can talk about the details. I have already sent an e-mail to several big companies that have the expertise needed to code the game, they haven't answer me. Actually the idea is nothing fancy, no 3D, but fun and unique.

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• The next next C++ [closed]

  - by Roger Pate

  It's entirely too early for speculation on what C++ will be like after C++0x, but idle hands make for wild predictions. What features would you find useful and why? Is there anything in another language that would fit nicely into the state of C++ after 0x? What should be considered for the next TC and TR? (Mostly TR, as the TC would depend more on what actually becomes the next standard.) Export was removed, rather than merely deprecated, in 0x. (It remains a keyword.) What other features carry so much baggage to also be more harmful than helpful? ISO Standards' process I'm not involved in the C++ committee, but it's also a mystery, unfortunately, to most programmers using C++. A few things worth keeping in mind: There will be 10 years between standards, barring extremely exceptional circumstances. The standard can get "bug fixes" in the form of a Technical Corrigendum. This happened to C++98 with TC1, named C++03. It fixed "simple" issues such as making the explicit guarantee that std::vector stores items contiguously, which was always intended. The committee can issue reports which can add to the language. This happened to C++98/03 with TR1 in 2005, which introduced the std::tr1 namespace.

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• Why not expose a primary key

  - by Angelo Neuschitzer

  In my education I have been told that it is a flawed idea to expose actual primary keys (not only DB keys, but all primary accessors) to the user. I always thought it to be a security problem (because an attacker could attempt to read stuff not their own). Now I have to check if the user is allowed to access anyway, so is there a different reason behind it? Also, as my users have to access the data anyway I will need to have a public key for the outside world somewhere in between. Now that public key has the same problems as the primary key, doesn't it?

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• Use adapter pattern for coupled classes

  - by kaiseroskilo

  I need (for unit testing purposes) to create adapters for external library classes.ExchangeService and ContactsFolder are Microsoft's implementations in its' EWS library. So I created my adapters that implement my interfaces, but it seems that contactsFolder has a dependency for ExchangeService in its' constructor. The problem is that I cannot instantiate ContactsFolderAdapter without somehow accessing the actual ExchangeService instance (I see only ExchangeServiceAdapter in scope). Is there a better pattern for this that retains the adapter classes? Or should I "infect" ExchangeServiceAdapter with some kind of GetActualObject method?

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• Are there specific legal issues for web developers working on sex dating sites?

  - by YumYumYum

  Say I have created many ordinary websites which are not related to any dating/sexual content. Are the rules and regulations for a developer the same when making a sex-related dating site? I'm talking about a site where people meet together and get to know each other, with the intent of having a sexual relationship (you know what I mean), also featuring webcam sex, but not explicitly a porno site. Do such sites have any special legal issues for developers compared with non-sexual/dating sites?

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• What to include in metadata?

  - by shyam

  I'm wondering if there are any general guidelines or best practices regarding when to split data into a metadata format, as oppose to directly embedding it within the data. (Specific example below). My understanding of metadata is that it describes data (without the need to actually look at the data), allowing for data to be quickly search/filtered for easy access. Let's take for example a simple 3D model format. The actual data file itself is a binary file containing vertices and colors. Things like creation date, modified data and author name would be things that describe the binary data, so I would say these belong as metadata (outside of the binary file). But what if the application had no need to search or filter by these fields? Would it be acceptable to embed these fields directly into the binary data itself? Could they be duplicated in both the binary data and the meta data, or would this be considered bad practice? What about more ambiguous fields such as the model name, which could be considered part of the data itself, but also as data describing the binary data?... How do you decide which data to embed in the actual binary file, as opposed to separating into a more flexible metadata format? Thanks!

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• Good free CSS Sprite for icons

  - by Saif Bechan

  I am working on a small project where I need some of the basic icons: edit, favorite, delete. You know them. Now i can download them all seperate, and put them together in a sprite, but I was wondering if there are ready to download sprites which I can use. Now I am working on an accounting app, so it would be nice if the icons were not too childish. A little but of fancy business type icons. Thanks

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