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• UML - Class Diagrams Order -> Products

  - by Phorce

  I have a class diagram that is like this: < Order > (1) CAN HAVE (M) < products > But therefore "Order" has the following: Order_Id Customer_Id Order_date_day Order_date_month Order_date_yeah But I do not know how it would handle the Products? Because, I couldn't have "ProductID" because that would mean that each item in this class would have to have a separate instance for each product (E.g. someone ordered 100 products, but only placed 1 order). Could I have an Product object in class Order? If so, how do you represent that in UML? Thank you

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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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• When following SRP, how should I deal with validating and saving entities?

  - by Kristof Claes

  I've been reading Clean Code and various online articles about SOLID lately, and the more I read about it, the more I feel like I don't know anything. Let's say I'm building a web application using ASP.NET MVC 3. Let's say I have a UsersController with a Create action like this: public class UsersController : Controller { public ActionResult Create(CreateUserViewModel viewModel) { } } In that action method I want to save a user to the database if the data that was entered is valid. Now, according to the Single Responsibility Principle an object should have a single responsibility, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility. Since validation and saving to the database are two separate responsibilities, I guess I should create to separate class to handle them like this: public class UsersController : Controller { private ICreateUserValidator validator; private IUserService service; public UsersController(ICreateUserValidator validator, IUserService service) { this.validator = validator; this.service= service; } public ActionResult Create(CreateUserViewModel viewModel) { ValidationResult result = validator.IsValid(viewModel); if (result.IsValid) { service.CreateUser(viewModel); return RedirectToAction("Index"); } else { foreach (var errorMessage in result.ErrorMessages) { ModelState.AddModelError(String.Empty, errorMessage); } return View(viewModel); } } } That makes some sense to me, but I'm not at all sure that this is the right way to handle things like this. It is for example entirely possible to pass an invalid instance of CreateUserViewModel to the IUserService class. I know I could use the built in DataAnnotations, but what when they aren't enough? Image that my ICreateUserValidator checks the database to see if there already is another user with the same name... Another option is to let the IUserService take care of the validation like this: public class UserService : IUserService { private ICreateUserValidator validator; public UserService(ICreateUserValidator validator) { this.validator = validator; } public ValidationResult CreateUser(CreateUserViewModel viewModel) { var result = validator.IsValid(viewModel); if (result.IsValid) { // Save the user } return result; } } But I feel I'm violating the Single Responsibility Principle here. How should I deal with something like this?

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• What good books are out there on program execution models? [on hold]

  - by murungu

  Can anyone out there name a few books that address the topic of program execution models?? I want a book that can answer questions such as... What is the difference between interpreted and compiled languages and what are the performance consequences at runtime?? What is the difference between lazy evaluation, eager evaluation and short circuit evaluation?? Why would one choose to use one evaluation strategy over another?? How do you simulate lazy evaluation in a language that favours eager evaluation??

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• CircuitLab Offers Easy Circuit Building on the Web and iPad

  - by Jason Fitzpatrick

  If you like to sketch out your circuit designs rapidly, cleanly, and on the web or your iPad, CircuitLab makes it dead simple. The free tool includes an easy drag-and-drop interface, circuit analysis, easy printing, and more. Watch the video above to see the creators of CircuitLab whipping up a simple circuit to showcase the app, then hit up the link below to try it out. CircuitLab [via Hacked Gadgets] How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me?

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• Beginning HTML and CSS [closed]

  - by romani

  My goal of learning HTML and CSS is to be able to modify popular scripts such as Wordpress, vBulletin, Drupal, etc. I haven't started yet learning CSS and HTML or XHTML. I see many, many books and tutorials out there so it is difficult to make a choice. I think most of web designers were like me in the past and have read many books. So, could you tell me about 1 good book for HTML and 1 good book for CSS? and if I should read the book from cover to cover or only learning the basics is enough for modifying Wordpress, for example!

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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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• Gamification: designing cooperation in an RPG like game based on Scrum methodology

  - by Grzegorz Slawecki

  I have implemented with 3 friends a gamified system at my work (development company) which builds an fantasy rpg game over scrum project methodology. Generally, the tasks are the missions, each player is represented by a character. They earn XPs for completing tasks and they advance to the next levels which gives them badges, titles and (this is in planning phase) new privileges (e.g. priority in choosing tasks). Since the very beginning we try to do everything to avoid rivalisation between players because it would ruin the project if the players started to compete. There are no explicit leaderboards, we also plan to give bonuses for helping other players. I have a feeling that this is still not enough to really encourage cooperation. I would like to ask You for any ideas that come to Your mind that would help.

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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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• Stuck at enemy movement

  - by Syed

  I am making a TD game in unity, Initially I made all of my enemy movements frame rate dependent say: I had a grid point1 at -22.65 and other at -21.1, diagrammatically: (-22.65) _________(-21.1)_______(-21.1+1.55) ...... so the distance on x axis between two points is 1.55, divided it by 25 jumps with each enemy jump of 0.062 of each frame. On reaching on next point of grid the enemy find again its path. All went fine until I have requirement of FastForward and Pause feature. I used timeScale property of unity but it wont work as they are frame dependent. I also tried double speed of enemy on clicking fast forward button at any time, it has some issues that enemy jumps are now less and it fails to reach on next grid point. Could someone suggest me solution to my problem. Do I need to change the enemy movement code to make it frame independent ?? I need the enemy to reach on the grid specific point I also need later to slow down any one enemy's speed when tower fires on it. Thnx

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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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• 2D pathfinding - finding smooth paths

  - by Kooi Nam Ng

  I was trying to implement a simple pathfinding, but the outcome is less satisfactory than what I intended to achieve. The thing is units in games like Starcraft 2 move in all directions whereas units in my case only move in at most 8 directions (Warcraft 1 style) as these 8 directions direct to next available nodes (they move from a tile to next neighboring tile). What should I do in order to achieve the result as in Starcraft 2? Shrink the tile size? On the picture you can see a horizontal line of rock tiles being obstacles, and the found path marked as green tiles. The red line is the path I want to achieve.

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• When to use abstract classes instead of interfaces and extension methods in C#?

  - by Gulshan

  "Abstract class" and "interface" are similar type of ideas, while interface being more abstract. One need of abstract classes was to provide method implementations for the derived classes. But in C#, that need has also been reduced by lately introduced extension methods. So, in C#, when should we use abstract classes instead of using interfaces and extension methods associated with the interface? And now, we can use 'Properties' in interfaces also. A notable example of interface+ extension methods is the Heavily used IEnumerable and it's helper methods. You use Linq and it's all by this extension methods!

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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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• Code and Slides: Techniques, Strategies, and Patterns for Structuring JavaScript Code

  - by dwahlin

  This presentation was given at the spring 2012 DevConnections conference in Las Vegas and is based on my Structuring JavaScript Code course from Pluralsight. The goal of the presentation is to show how closures combined with code patterns can be used to provide structure to JavaScript code and make it more re-useable, maintainable, and less susceptible to naming conflicts.  Topics covered include: Closures Using Object literals Namespaces The Prototype Pattern The Revealing Module Pattern The Revealing Prototype Pattern View more of my presentations here. Sample code from the presentation can be found here. Check out the full-length course on the topic at Pluralsight.com.

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• Making fonts render similarly across browsers

  - by Zach L.

  I am building a website for a client, and we had hoped to use plain text, not images in the navigation bar. The font we are using is Century Gothic (I believe that this font is available on the majority of PCs and Macs) The problem is, that on different browsers the font renders significantly differnt. In Chrome we got it looking the way we want, but in firefox the text is smaller and bolder. Aside from writing browser specific javascript to alter the font properties, are there any other options to standardize the way the fonts are rendered cross-browser. Perhaps some library or API? Maybe its a matter of being more specific in declaring font properties? Honestly I am stuck and need help.

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• What source code organization approach helps improve modularity and API/Implementation separation?

  - by Berin Loritsch

  Few languages are as restrictive as Java with file naming standards and project structure. In that language, the file name must match the public class declared in the file, and the file must live in a directory structure matching the class package. I have mixed feelings about that approach. While I never have to guess where a file lives, there's still a lot of empty directories and artificial constraints. There's several languages that define everything about a class in one file, at least by convention. C#, Python (I think), Ruby, Erlang, etc. The commonality in most these languages is that they are object oriented, although that statement can probably be rebuffed (there is one non-OO language in the list already). Finally, there's quite a few languages mostly in the C family that have a separate header and implementation file. For C I think this makes sense, because it is one of the few ways to separate the API interface from implementations. With C it seems that feature is used to promote modularity. Yet, with C++ the way header and implementation files are split seems rather forced. You don't get the same clean API separation that you do with C, and you are forced to include some private details in the header you would rather keep only in the implementation. There's quite a few languages that have a concept that overlaps with interfaces like Java, C#, Go, etc. Some languages use what feels like a hack to provide the same concept like C# using pure virtual abstract classes. Still others don't really have an interface concept and rely on "duck" typing--for example Ruby. Ruby has modules, but those are more along the lines of mixing in behaviors to a class than they are for defining how to interact with a class. In OO terms, interfaces are a powerful way to provide separation between an API client and an API implementation. So to hurry up and ask the question, from a personal experience point of view: Does separation of header and implementation help you write more modular code, or does it get in the way? (it helps to specify the language you are referring to) Does the strict file name to class name scheme of Java help maintainability, or is it unnecessary structure for structure's sake? What would you propose to promote good API/Implementation separation and project maintenance, how would you prefer to do it?

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• Sounds to describe the weather?

  - by Matthew

  I'm trying to think of sounds that will help convey the time of day and weather condition. I'm not even sure of all the weather conditions I would consider, and some are obvious. Like if it's raining, the sound of rain. But then I'm thinking, what about for a calm day? If it's morning time, I could do birds chirping or something. Night time could be an owl or something. What are some good combinations of sounds/weather/time to have a good effect?

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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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• Recommended method towards making custom maps for a 2d game?

  - by Qasim

  I am planning on making a 2D game, however different from my last personal projects I want this one to have enhanced graphics, with custom-designed levels. My previous 2d platformers were tile-based, in which I made a map editor for to create levels. However, I am wondering the best way to implement custom designed maps? For say, some grass is a litter higher than others, flowers here and there, cool drawings and structures along the way, etc. instead of just the same old tiles over and over again. I am thinking but I just can't grasp the idea of how to implement it. I have seen it done in other games and am interested to see how they accomplish it, but can't get my hands on some source code. :(

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• How to manage own bots at the server?

  - by Nikolay Kuznetsov

  There is a game server and people can play in game rooms of 2, 3 or 4. When a client connects to server he can send a request specifying a number of people or range he wants to play with. One of this value is valid: {2-4, 2-3, 3-4, 2, 3, 4} So the server maintains 3 separate queues for game room with 2, 3 and 4 people. So we can denote queues as #2, #3 and #4. It work the following way. If a client sends request, 3-4, then two separate request are added to queues #3 and #4. If queue #3 now have 3 requests from different people then game room with 3 players is created, and all other requests from those players are removed from all queues. Right now not many people are online simultaneously, so they apply for a game wait for some time and quit because game does not start in a reasonable time. That's a simple bot for beginning has been developed. So there is a need to patch server code to run a bot, if some one requests a game, but humans are not online. Input: request from human {2-4, 2-3, 3-4, 2, 3, 4} Output: number of bots to run and time to wait for each before connecting, depending on queues state. The problem is that I don't know how to manage bots properly at the server? Example: #3 has 1 request and #4 has 1 request Request from user is {3,4} then server can add one bot to play game with 3 people or two bots to play game of 4. Example: #3 has 1 request and #4 has 2 requests Request from user is {3,4} then in each case just one bot is needed so game with 4 players is more preferrable.

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• String patterns that can be used to filter and group files

  - by Louis Rhys

  One of our application filters files in certain directory, extract some data from it and export a document from the extracted data. The algorithm for extracting the data depends on the file, and so far we use regex to select the algorithm to be used, for example .*\.txt will be processed by algorithm A, foo[0-5]\.xml will be processed by algo B, etc. However now we need some files to be processed together. For example, in one case we need two files, foo.*\.xml and bar.*\.xml. Part of the information to be extracted exist in the foo file, and the other part in the bar file. Moreover, we need to make sure the wild card is compatible. For example, if there are 6 files foo1.xml foo23.xml bar1.xml bar9.xml bar23.xml foo4.xml I would expect foo1 and bar1 to be identified as a group, and foo23 and bar23 as another group. bar9 and foo4 has no pair, so they will not be treated. Now, since the filter is configured by user, we need to have a pattern that can express the above requirement. I don't think you can express meaning like above in standard regex. (foo|bar).*\.xml will match all 6 file above and we can't identify which file is paired for a particular file. Is there any standard pattern that can express it? Or any idea how to modify regex to support this, that can be implemented easily?

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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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• How to refactor and improve this XNA mouse input code?

  - by Andrew Price

  Currently I have something like this: public bool IsLeftMouseButtonDown() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Pressed; } public bool IsLeftMouseButtonPressed() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonUp() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonReleased() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Pressed; } This is fine. In fact, I kind of like it. However, I'd hate to have to repeat this same code five times (for right, middle, X1, X2). Is there any way to pass in the button I want to the function so I could have something like this? public bool IsMouseButtonDown(MouseButton button) { return currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonPressed(MouseButton button) { return currentMouseState.IsPressed(button) && !previousMouseState.IsPressed(button); } public bool IsMouseButtonUp(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonReleased(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } I suppose I could create some custom enumeration and switch through it in each function, but I'd like to first see if there is a built-in solution or a better way.. Thanks!

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• Relationship between Repository and Unit of Work

  - by NullOrEmpty

  I am going to implement a repository, and I would like to use the UOW pattern since the consumer of the repository could do several operations, and I want to commit them at once. After read several articles about the matter, I still don't get how to relate this two elements, depending on the article it is being done in a way u other. Sometimes the UOW is something internal to the repository: public class Repository { UnitOfWork _uow; public Repository() { _uow = IoC.Get<UnitOfWork>(); } public void Save(Entity e) { _uow.Track(e); } public void SubmittChanges() { SaveInStorage(_uow.GetChanges()); } } And sometimes it is external: public class Repository { public void Save(Entity e, UnitOfWork uow) { uow.Track(e); } public void SubmittChanges(UnitOfWork uow) { SaveInStorage(uow.GetChanges()); } } Other times, is the UOW whom references the Repository public class UnitOfWork { Repository _repository; public UnitOfWork(Repository repository) { _repository = repository; } public void Save(Entity e) { this.Track(e); } public void SubmittChanges() { _repository.Save(this.GetChanges()); } } How are these two elements related? UOW tracks the elements that needs be changed, and repository contains the logic to persist those changes, but... who call who? Does the last make more sense? Also, who manages the connection? If several operations have to be done in the repository, I think using the same connection and even transaction is more sound, so maybe put the connection object inside the UOW and this one inside the repository makes sense as well. Cheers

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