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• Should I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority?

  - by JonathonG

  Can I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority, and is it a good idea? Here's more info: I am about to begin work on porting a mid-sized game from Flash/AS3 to Java so that I can continue development with multi-threading capabilities. Here's a small bit of background about the game: The game contains numerous asynchronous activities, such as "world updating" (the game environment is constantly changing based on a set of natural laws and forces), procedural generation of terrain, NPCs, quests, items, etc., and on top of that, the effects of all of the player's interactions with his environment are programmatically calculated in real time, based on a set of constantly changing "stats" and once again, natural laws and forces. All of these things going on at once, in an asynchronous manner, seem to lend themselves to multi-threading very well. My question is: Can I build some kind of central engine that handles the "stacking" of all of these events as they are triggered, and dynamically sorts them out amongst the available threads, and would it be a good idea? As an example: Essentially, every time something happens (IE, a magic missile being generated by a spell, or a bunch of plants need to grow to their next stage), instead of just processing that task right then and adding the new object(s) to a list of managed objects, send a reference to that event to a core "event handler" that throws it into a stack of all other currently queued events, which then sorts them out and orders them according to urgency, splits them between a number of available threads for as-fast-as-possible multithreaded execution.

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• Help with design structure choice: Using classes or library of functions

  - by roverred

  So I have GUI Class that will call another class called ImageProcessor that contains a bunch functions that will perform image processing algorithms like edgeDetection, gaussianblur, contourfinding, contour map generations, etc. The GUI passes an image to ImageProcessor, which performs one of those algorithm on it and it returns the image back to the GUI to display. So essentially ImageProcessor is a library of independent image processing functions right now. It is called in the GUI like so Image image = ImageProcessor.EdgeDetection(oldImage); Some of the algorithms procedures require many functions, and some can be done in a single function or even one line. All these functions for the algorithms jam packed into ImageProcessor can be pretty messy, and ImageProcessor doesn't sound it should be a library. So I was thinking about making every algorithm be a class with a shared interface say IAlgorithm. Then I pass the IAlgorithm interface from the GUI to the ImageProcessor. public interface IAlgorithm{ public Image Process(); } public class ImageProcessor{ public Image Process(IAlgorithm TheAlgorithm){ return IAlgorithm.Process(); } } Calling in the GUI like so Image image = ImageProcessor.Process(new EdgeDetection(oldImage)); I think it makes sense in an object point of view, but the problem is I'll end up with some classes that are just one function. What do you think is a better design, or are they both crap and you have a much better idea? Thanks!

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• Avoiding bloated Domain Objects

  - by djcredo

  We're trying to move data from our bloated Service layer into our Domain layer using a DDD approach. We currently have a lot of business logic in our services, which is spread out all over the place and doesn't benefit from inheritance. We have a central Domain class which is the focus of most of our work - a Trade. The Trade object will know how to price itself, how to estimate risk, validate itself, etc. We can then replace conditionals with polymorphism. Eg: SimpleTrade will price itself one way, but ComplexTrade will price itself another. However, we are worried that this will bloat the Trade class(s). It really should be in charge of its own processing but the class size is going to increase exponentially as more features are added. So we have choices: Put processing logic in Trade class. Processing logic is now polymorphic based on the type of the trade, but Trade class is now has multiple responsibilites (pricing, risk, etc) and is large Put processing logic into other class such as TradePricingService. No longer polymorphic with the Trade inheritance tree, but classes are smaller and easier to test. What would be the suggested approach?

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• What OO Design to use ( is there a Design Pattern )?

  - by Blundell

  I have two objects that represent a 'Bar/Club' ( a place where you drink/socialise). In one scenario I need the bar name, address, distance, slogon In another scenario I need the bar name, address, website url, logo So I've got two objects representing the same thing but with different fields. I like to use immutable objects, so all the fields are set from the constructor. One option is to have two constructors and null the other fields i.e: class Bar { private final String name; private final Distance distance; private final Url url; public Bar(String name, Distance distance){ this.name = name; this.distance = distance; this.url = null; } public Bar(String name, Url url){ this.name = name; this.distance = null; this.url = url; } // getters } I don't like this as you would have to null check when you use the getters In my real example the first scenario has 3 fields and the second scenario has about 10, so it would be a real pain having two constructors, the amount of fields I would have to declare null and then when the object are in use you wouldn't know which Bar you where using and so what fields would be null and what wouldn't. What other options do I have? Two classes called BarPreview and Bar? Some type of inheritance / interface? Something else that is awesome?

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• My proposed design is usually worse than my colleague's - how do I get better?

  - by user151193

  I have been programming for couple of years and am generally good when it comes to fixing problems and creating small-to-medium scripts, however, I'm generally not good at designing large scale programs in object oriented way. Few questions Recently, a colleague who has same number of years of experience as me and I were working on a problem. I was working on a problem longer than him, however, he came up with a better solution and in the end we're going to use his design. This really affected me. I admit his design is better, but I wanted to come up with a design as good as his. I'm even contemplating quitting the job. Not sure why but suddenly I feel under some pressure e.g. what would juniors think of me and etc? Is it normal? Or I'm thinking a little too much into this? My job involves programming in Python. I try to read source code but how do you think I can improve me design skills? Are there any good books or software that I should study? Please enlighten me. I will really appreciate your help.

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• How to Correct & Improve the Design of this Code?

  - by DaveDev

  HI Guys, I've been working on a little experiement to see if I could create a helper method to serialize any of my types to any type of HTML tag I specify. I'm getting a NullReferenceException when _writer = _viewContext.Writer; is called in protected virtual void Dispose(bool disposing) {/*...*/} I think I'm at a point where it almost works (I've gotten other implementations to work) and I was wondering if somebody could point out what I'm doing wrong? Also, I'd be interested in hearing suggestions on how I could improve the design? So basically, I have this code that will generate a Select box with a number of options: // the idea is I can use one method to create any complete tag of any type // and put whatever I want in the content area <% using (Html.GenerateTag<SelectTag>(Model, new { href = Url.Action("ActionName") })) { %> <%foreach (var fund in Model.Funds) {%> <% using (Html.GenerateTag<OptionTag>(fund)) { %> <%= fund.Name %> <% } %> <% } %> <% } %> This Html.GenerateTag helper is defined as: public static MMTag GenerateTag<T>(this HtmlHelper htmlHelper, object elementData, object attributes) where T : MMTag { return (T)Activator.CreateInstance(typeof(T), htmlHelper.ViewContext, elementData, attributes); } Depending on the type of T it'll create one of the types defined below, public class HtmlTypeBase : MMTag { public HtmlTypeBase() { } public HtmlTypeBase(ViewContext viewContext, params object[] elementData) { base._viewContext = viewContext; base.MergeDataToTag(viewContext, elementData); } } public class SelectTag : HtmlTypeBase { public SelectTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("select"); //base.MergeDataToTag(viewContext, elementData); } } public class OptionTag : HtmlTypeBase { public OptionTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("option"); //base.MergeDataToTag(viewContext, _elementData); } } public class AnchorTag : HtmlTypeBase { public AnchorTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("a"); //base.MergeDataToTag(viewContext, elementData); } } all of these types (anchor, select, option) inherit from HtmlTypeBase, which is intended to perform base.MergeDataToTag(viewContext, elementData);. This doesn't happen though. It works if I uncomment the MergeDataToTag methods in the derived classes, but I don't want to repeat that same code for every derived class I create. This is the definition for MMTag: public class MMTag : IDisposable { internal bool _disposed; internal ViewContext _viewContext; internal TextWriter _writer; internal TagBuilder _tag; internal object[] _elementData; public MMTag() {} public MMTag(ViewContext viewContext, params object[] elementData) { } public void Dispose() { Dispose(true /* disposing */); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (!_disposed) { _disposed = true; _writer = _viewContext.Writer; _writer.Write(_tag.ToString(TagRenderMode.EndTag)); } } protected void MergeDataToTag(ViewContext viewContext, object[] elementData) { Type elementDataType = elementData[0].GetType(); foreach (PropertyInfo prop in elementDataType.GetProperties()) { if (prop.PropertyType.IsPrimitive || prop.PropertyType == typeof(Decimal) || prop.PropertyType == typeof(String)) { object propValue = prop.GetValue(elementData[0], null); string stringValue = propValue != null ? propValue.ToString() : String.Empty; _tag.Attributes.Add(prop.Name, stringValue); } } var dic = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase); var attributes = elementData[1]; if (attributes != null) { foreach (PropertyDescriptor descriptor in TypeDescriptor.GetProperties(attributes)) { object value = descriptor.GetValue(attributes); dic.Add(descriptor.Name, value); } } _tag.MergeAttributes<string, object>(dic); _viewContext = viewContext; _viewContext.Writer.Write(_tag.ToString(TagRenderMode.StartTag)); } } Thanks Dave

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• Compare-Object gives false differences

  - by Andy

  I have some problem with Compare-Object. My task is to get difference between two directory snapshots made at different times. First snapshot is taken like this: ls -recurse d:\dir | export-clixml dir-20100129.xml Then, later, I get second snapshot and load both of them: $b = (import-clixml dir-20100130.xml) $a = (import-clixml dir-20100129.xml) Next, I'm trying to compare with Compare-Object, like that: diff $a $b What I get is in some places files that were added to $b since $a, but in some -- files that were in both snapshots, and some files, that were added to $b, are not given in Compare-Object output. Puzzling, but $b.count - $a.count is EXACTLY the same as (diff $a $b).count. Why is that? Ok, Compare-Object has -property param. I try to use that: diff -property fullname $a $b And I get the whole mess of differences: it shows me ALL the files. For example, say $a contains: A\1.txt A\2.txt A\3.txt And $b contains: X\2.mp3 X\3.mp3 X\4.mp3 A\1.txt A\2.txt A\3.txt diff output is something like that: X\2.mp3 => A\1.txt <= X\3.mp3 => A\2.txt <= X\4.mp3 => A\3.txt <= A\1.txt => A\2.txt => A\3.txt => Weird. I think I don't understand something crucial about Compare- Object usage, and manuals are scarce... Please, help me to get the DIFFERENCE between two directory snapshots. Thanks in advance UPDATE: I've saved data as plain strings like that: > import-clixml dir-20100129.xml | % { $_.fullname } | out-file -enc utf8 a.txt And results are the same. Here're excerpts of both snapshots (top 100-something lines, a.txt and b.txt), output of compare-object, and output of UNIX diff (unified). All files are UTF-8: http://dl.dropbox.com/u/2873752/compare-object-problem.zip

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• Constructor and Destructor of a singleton object called twice

  - by Bikram990

  I'm facing a problem in singleton object in c++. Here is the explanation: Problem info: I have a 4 shared libraries (say libA.so, libB.so, libC.so, libD.so) and 2 executable binary files each using one another shared library( say libE.so) which deals with files. The purpose of libE.so is to write data into a file and if the executable restarts or size of file exceeds a certain limit it is zipped and a new file is created with time stamp in name. It is using singleton object. It exports a handler class for getting and using singleton. Compressing only happens in the above said two cases. The user/loader executable can specify the starting name of file only no other control is provided by handler class. libA.so, libB.so, libC.so and libD.so have almost same behavior. They all have a class and declare and object of an handler which gets the instance of the singleton in libE.so and uses it for further purpose. All these libraries are linked to two executable binary files. If only one of the two executable runs then its fine, But if both executable runs one after other then the file of the first started executable gets compressed. Debug info: The constructor and destructor of the singleton object is called twice.(for each executable) The object of singleton is a static object and never deleted. The executable is not able to exit/return gives: glibc detected * (exe1 or exe2): double free or corruption (!prev): some_addr * Running with binaries valgrind gives that the above error is due to the destructor of the singleton object. Thanks

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• Do I suffer from encapsulation overuse?

  - by Florenc

  I have noticed something in my code in various projects that seems like code smell to me and something bad to do, but I can't deal with it. While trying to write "clean code" I tend to over-use private methods in order to make my code easier to read. The problem is that the code is indeed cleaner but it's also more difficult to test (yeah I know I can test private methods...) and in general it seems a bad habit to me. Here's an example of a class that reads some data from a .csv file and returns a group of customers (another object with various fields and attributes). public class GroupOfCustomersImporter { //... Call fields .... public GroupOfCustomersImporter(String filePath) { this.filePath = filePath; customers = new HashSet<Customer>(); createCSVReader(); read(); constructTTRP_Instance(); } private void createCSVReader() { //.... } private void read() { //.... Reades the file and initializes the class attributes } private void readFirstLine(String[] inputLine) { //.... Method used by the read() method } private void readSecondLine(String[] inputLine) { //.... Method used by the read() method } private void readCustomerLine(String[] inputLine) { //.... Method used by the read() method } private void constructGroupOfCustomers() { //this.groupOfCustomers = new GroupOfCustomers(**attributes of the class**); } public GroupOfCustomers getConstructedGroupOfCustomers() { return this.GroupOfCustomers; } } As you can see the class has only a constructor which calls some private methods to get the job done, I know that's not a good practice not a good practice in general but I prefer to encapsulate all the functionality in the class instead of making the methods public in which case a client should work this way: GroupOfCustomersImporter importer = new GroupOfCustomersImporter(filepath) importer.createCSVReader(); read(); GroupOfCustomer group = constructGoupOfCustomerInstance(); I prefer this because I don't want to put useless lines of code in the client's side code bothering the client class with implementation details. So, Is this actually a bad habit? If yes, how can I avoid it? Please note that the above is just a simple example. Imagine the same situation happening in something a little bit more complex.

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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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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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• 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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• How far should an entity take care of its properties values by itself?

  - by Kharlos Dominguez

  Let's consider the following example of a class, which is an entity that I'm using through Entity Framework. - InvoiceHeader - BilledAmount (property, decimal) - PaidAmount (property, decimal) - Balance (property, decimal) I'm trying to find the best approach to keep Balance updated, based on the values of the two other properties (BilledAmount and PaidAmount). I'm torn between two practices here: Updating the balance amount every time BilledAmount and PaidAmount are updated (through their setters) Having a UpdateBalance() method that the callers would run on the object when appropriate. I am aware that I can just calculate the Balance in its getter. However, it isn't really possible because this is an entity field that needs to be saved back to the database, where it has an actual column, and where the calculated amount should be persisted to. My other worry about the automatically updating approach is that the calculated values might be a little bit different from what was originally saved to the database, due to rounding values (an older version of the software, was using floats, but now decimals). So, loading, let's say 2000 entities from the database could change their status and make the ORM believe that they have changed and be persisted back to the database the next time the SaveChanges() method is called on the context. It would trigger a mass of updates that I am not really interested in, or could cause problems, if the calculation methods changed (the entities fetched would lose their old values to be replaced by freshly recalculated ones, simply by being loaded). Then, let's take the example even further. Each invoice has some related invoice details, which also have BilledAmount, PaidAmount and Balance (I'm simplifying my actual business case for the sake of the example, so let's assume the customer can pay each item of the invoice separately rather than as a whole). If we consider the entity should take care of itself, any change of the child details should cause the Invoice totals to change as well. In a fully automated approach, a simple implementation would be looping through each detail of the invoice to recalculate the header totals, every time one the property changes. It probably would be fine for just a record, but if a lot of entities were fetched at once, it could create a significant overhead, as it would perform this process every time a new invoice detail record is fetched. Possibly worse, if the details are not already loaded, it could cause the ORM to lazy-load them, just to recalculate the balances. So far, I went with the Update() method-way, mainly for the reasons I explained above, but I wonder if it was right. I'm noticing I have to keep calling these methods quite often and at different places in my code and it is potential source of bugs. It also has a detrimental effect on data-binding because when the properties of the detail or header changes, the other properties are left out of date and the method has no way to be called. What is the recommended approach in this case?

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• Should library classes be wrapped before using them in unit testing?

  - by Songo

  I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Example: class Logger{ private $mailer; function __construct(Zend_Mail $mail){ $this->mail=$mail; } function toBeTestedFunction(){ //Some code $this->mail->setTo('some value'); $this->mail->setSubject('some value'); $this->mail->setBody('some value'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Does that mean that I can never use a library class directly and must always wrap it in a class of my own? Example: interface Mailer{ public function setTo($to); public function setSubject($subject); public function setBody($body); public function send(); } class MyMailer implements Mailer{ private $mailer; function __construct(){ $this->mail=new Zend_Mail; //The class isn't injected this time } function setTo($to){ $this->mailer->setTo($to); } //implement the rest of the interface functions similarly } And now my Logger class can be happy :D class Logger{ private $mailer; function __construct(Mailer $mail){ $this->mail=$mail; } //rest of the code unchanged } Questions: Although I solved the mocking problem by introducing an interface, I have created a totally new class Mailer that now needs to be unit tested although it only wraps Zend_Mail which is already unit tested by the Zend team. Is there a better approach to all this? Zend_Mail's send() function could actually have a Zend_Transport object when called (i.e. public function send($transport = null)). Does this make the idea of a wrapper class more appealing? The code is in PHP, but answers doesn't have to be. This is more of a design issue than a language specific feature

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• PHP - Internal APIs/Libraries - What makes sense?

  - by Mark Locker

  I've been having a discussion lately with some colleagues about the best way to approach a new project, and thought it'd be interesting to get some external thoughts thrown into the mix. Basically, we're redeveloping a fairly large site (written in PHP) and have differing opinions on how the platform should be setup. Requirements: The platform will need to support multiple internal websites, as well as external (non-PHP) projects which at the moment consist of a mobile app and a toolbar. We have no plans/need in the foreseeable future to open up an API externally (for use in products other than our own). My opinion: We should have a library of well documented native model classes which can be shared between projects. These models will represent everything in our database and can take advantage of object orientated features such as inheritance, traits, magic methods, etc. etc. As well as employing ORM. We can then add an API layer on top of these models which can basically accept requests and route them to the appropriate methods, translating the response so that it can be used platform independently. This routing for each method can be setup as and when it's required. Their opinion: We should have a single HTTP API which is used by all projects (internal PHP ones or otherwise). My thoughts: To me, there are a number of issues with using the sole HTTP API approach: It will be very expensive performance wise. One page request will result in several additional http requests (which although local, are still ones that Apache will need to handle). You'll lose all of the best features PHP has for OO development. From simple inheritance, to employing the likes of ORM which can save you writing a lot of code. For internal projects, the actual process makes me cringe. To get a users name, for example, a request would go out of our box, over the LAN, back in, then run through a script which calls a method, JSON encodes the output and feeds that back. That would then need to be JSON decoded, and be presented as an array ready to use. Working with arrays, as appose to objects, makes me sad in a modern PHP framework. Their thoughts (and my responses): Having one method of doing thing keeps things simple. - You'd only do things differently if you were using a different language anyway. It will become robust. - Seeing as the API will run off the library of models, I think my option would be just as robust. What do you think? I'd be really interested to hear the thoughts of others on this, especially as opinions on both sides are not founded on any past experience.

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• Does OO, TDD, and Refactoring to Smaller Functions affect Speed of Code?

  - by Dennis

  In Computer Science field, I have noticed a notable shift in thinking when it comes to programming. The advice as it stands now is write smaller, more testable code refactor existing code into smaller and smaller chunks of code until most of your methods/functions are just a few lines long write functions that only do one thing (which makes them smaller again) This is a change compared to the "old" or "bad" code practices where you have methods spanning 2500 lines, and big classes doing everything. My question is this: when it call comes down to machine code, to 1s and 0s, to assembly instructions, should I be at all concerned that my class-separated code with variety of small-to-tiny functions generates too much extra overhead? While I am not exactly familiar with how OO code and function calls are handled in ASM in the end, I do have some idea. I assume that each extra function call, object call, or include call (in some languages), generate an extra set of instructions, thereby increasing code's volume and adding various overhead, without adding actual "useful" code. I also imagine that good optimizations can be done to ASM before it is actually ran on the hardware, but that optimization can only do so much too. Hence, my question -- how much overhead (in space and speed) does well-separated code (split up across hundreds of files, classes, and methods) actually introduce compared to having "one big method that contains everything", due to this overhead? UPDATE for clarity: I am assuming that adding more and more functions and more and more objects and classes in a code will result in more and more parameter passing between smaller code pieces. It was said somewhere (quote TBD) that up to 70% of all code is made up of ASM's MOV instruction - loading CPU registers with proper variables, not the actual computation being done. In my case, you load up CPU's time with PUSH/POP instructions to provide linkage and parameter passing between various pieces of code. The smaller you make your pieces of code, the more overhead "linkage" is required. I am concerned that this linkage adds to software bloat and slow-down and I am wondering if I should be concerned about this, and how much, if any at all, because current and future generations of programmers who are building software for the next century, will have to live with and consume software built using these practices. UPDATE: Multiple files I am writing new code now that is slowly replacing old code. In particular I've noted that one of the old classes was a ~3000 line file (as mentioned earlier). Now it is becoming a set of 15-20 files located across various directories, including test files and not including PHP framework I am using to bind some things together. More files are coming as well. When it comes to disk I/O, loading multiple files is slower than loading one large file. Of course not all files are loaded, they are loaded as needed, and disk caching and memory caching options exist, and yet still I believe that loading multiple files takes more processing than loading a single file into memory. I am adding that to my concern.

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• Type Object does not support slicing Unity3D

  - by Vish

  I am getting the following error in my code and I can't seem to understand why. Can anyone help me with it? This is my current code. The line causing the error is marked in a comment near the end. var rows : int = 4; var cols : int = 4; var totalCards : int = cols * rows; var matchesNeedToWin : int = totalCards * 0.5; var matchesMade : int = 0; var cardW : int = 100; var cardH : int = 100; var aCards : Array; var aGrid : Array; // This Array will store the two cards that the player flipped var aCardsFlipped : ArrayList; // To prevent player from clicking buttons when we don't want him to var playerCanClick : boolean; var playerHasWon : boolean = false; class Card extends System.Object { var isFaceUp : boolean = false; var isMatched : boolean = false; var img : String; function Card () { img = "robot"; } } function Start () { var i : int = 0; var j : int = 0; playerCanClick = true; aCards = new Array (); aGrid = new Array (); aCardsFlipped = new ArrayList (); for ( i = 0; i < rows; i++) { aGrid [i] = new Array (); for (j = 0; j < cols; cols++ ) { aGrid [i] [j] = new Card (); // <------ Error over here } } } function Update () { Debug.Log("Game Screen has loaded"); } The error states as follows: Error BCE0048: Type 'Object' does not support slicing. (BCE0048) (Assembly-UnityScript)

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• Transforming object world space matrix to a position in world space

  - by Fredrik Boston Westman

  Im trying to make a function for picking objects with a bounding sphere however I have run in to a problem. First I check against my my bounding sphere, then if it checks out then I test against the vertexes. I have already tested my vertex picking method and it work fine, however when I check first with my bounding sphere method it dosnt register anything. My conclusion is that when im transform my sphere position in to the position of the object in world space, the transformation goes wrong ( I base this on the fact the the x coordinate always becomes 1, even tho i translate non of my meshes along the x-axis to 1). So my question is: What is the proper way to transform a objects world space matrix to a position vector ? This is how i do it now: First i set my position vector to 0. XMVECTOR meshPos = XMVectorSet(0.0f, 0.0f, 0.0f, 0.0f); Then I trannsform it with my object space matrix, and then add the offset to the center of the mesh. meshPos = XMVector3TransformCoord(meshPos, meshWorld) + centerOffset;

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• Oracle SQL Developer: Single Object Compare

  - by thatjeffsmith

  There’s a nasty rumor going around that you can’t compare database objects and/or code in Oracle SQL Developer. So let’s put that to bed right now. First, here’s how to compare: PL/SQL to PL/SQL or a SQL statement to another SQL statement So now that that’s settled, why don’t we take a look at how to compare a single table, to another table – whether it’s in the same database or a different database. Database Diff There’s no additional licensing requirement here. If you have SQL Developer, you can use this feature. if you’re going to compare 1 table to another, make sure you ONLY have ‘tables’ checked And then, use this dialog to select your table(s): Move over the object(s) you want to compare over to the right hand side. And now we can move onto the results. The differences, side-by-side, and the script to make B look like A Common lines with differences are highlighted in blue, new lines are highlighted in red. So that’s why they are different, but here’s the script to synch up the differences: Read the script, TEST the script, apply the script. And that’s it. Well, that’s mostly it. If you have questions about how to compare a database object in a schema you don’t have the login information for, read this post next.

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• How to move the object around the screen

  - by Abhishek

  I am trying to move the object around the screen I try this code -(void) move { CGFloat upperLimit = mWinSize.height - (mGunda.contentSize.height / 2.0); CGFloat upperLimit1 = mWinSize.height; CGFloat lowerLimit = (mGunda.contentSize.height / 2.0); CGFloat RightLimit = mWinSize.width - (mGunda.contentSize.width/2.0); CGFloat Right = (mGunda.contentSize.width/2.0); if ( mImageGoingUpward ) { mGunda.position = ccp( mGunda.position.x, mGunda.position.y + 5); if ( mGunda.position.y >= upperLimit ) { mImageGoingUpward = NO; mHori = NO; } } else { mGunda.position = ccp( mGunda.position.x, mGunda.position.y - 5); if ( mGunda.position.y <= lowerLimit ) { mGunda.position = ccp(mGunda.position.x +5, lowerLimit); } if(mGunda.position.x >= RightLimit) { mGunda.position = ccp(mGunda.position.x, mGunda.position.y+10); mHori = YES; } if(mHori) { if(mGunda.position.y >= upperLimit) { mGunda.position = ccp(mGunda.position.x - 5,mGunda.position.y); } } } } } It move the object from bottom to top & top to bottom & bottom to right & right to right top of the screen here is problem I have got It not move to the right top to left side of screen this rotationis not happen. How can I do this

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• Yet Another Way To Create An Object

  - by Ricardo Peres

  After I wrote this post, I come up with yet another way to create an object... Here it is: Stopwatch watch = new Stopwatch(); ConstructorInfo ci = typeof(StringBuilder).GetConstructor(new Type[0]); NewExpression expr = Expression.New(ci); Func<StringBuilder> func = Expression.Lambda(typeof(Func<StringBuilder>), expr).Compile() as Func<StringBuilder>; watch.Start(); for (Int32 i = 0; i < 100; ++i) { StringBuilder builder = func(); } Int64 time4 = watch.ElapsedTicks; watch.Reset(); I know of only one other way, which is by using CodeDOM. If you know of any other ways to create an object, let me know! SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• Checking if an object is inside bounds of an isometric chunk

  - by gopgop

  How would I check if an object is inside the bounds of an isometric chunk? for example I have a player and I want to check if its inside the bounds of this isometric chunk. I draw the isometric chunk's tiles using OpenGL Quads. My first try was checking in a square pattern kind of thing: e = object; this = isometric chunk; if (e.getLocation().getX() < this.getLocation().getX()+World.CHUNK_WIDTH*World.TILE_WIDTH && e.getLocation().getX() > this.getLocation().getX()) { if (e.getLocation().getY() > this.getLocation().getY() && e.getLocation().getY() < this.getLocation().getY()+World.CHUNK_HEIGHT*World.TILE_HEIGHT) { return true; } } return false; What happens here is that it checks in a SQUARE around the chunk so not the real isometric bounds. Image example: (THE RED IS WHERE THE PROGRAM CHECKS THE BOUNDS) What I have now: Desired check: Ultimately I want to do the same for each tile in the chunk. EXTRA INFO: Till now what I had in my game is you could only move tile by tile but now I want them to move freely but I still need them to have a tile location so no matter where they are on the tile their tile location will be that certain tile. then when they are inside a different tile's bounding box then their tile location becomes the new tile. Same thing goes with chunks. the player does have an area but the area does not matter in this case. and as long as the X and Y are inside the bounding box then it should return true. they don't have to be completely on the tile.

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• Switch or a Dictionary when assigning to new object

  - by KChaloux

  Recently, I've come to prefer mapping 1-1 relationships using Dictionaries instead of Switch statements. I find it to be a little faster to write and easier to mentally process. Unfortunately, when mapping to a new instance of an object, I don't want to define it like this: var fooDict = new Dictionary<int, IBigObject>() { { 0, new Foo() }, // Creates an instance of Foo { 1, new Bar() }, // Creates an instance of Bar { 2, new Baz() } // Creates an instance of Baz } var quux = fooDict[0]; // quux references Foo Given that construct, I've wasted CPU cycles and memory creating 3 objects, doing whatever their constructors might contain, and only ended up using one of them. I also believe that mapping other objects to fooDict[0] in this case will cause them to reference the same thing, rather than creating a new instance of Foo as intended. A solution would be to use a lambda instead: var fooDict = new Dictionary<int, Func<IBigObject>>() { { 0, () => new Foo() }, // Returns a new instance of Foo when invoked { 1, () => new Bar() }, // Ditto Bar { 2, () => new Baz() } // Ditto Baz } var quux = fooDict[0](); // equivalent to saying 'var quux = new Foo();' Is this getting to a point where it's too confusing? It's easy to miss that () on the end. Or is mapping to a function/expression a fairly common practice? The alternative would be to use a switch: IBigObject quux; switch(someInt) { case 0: quux = new Foo(); break; case 1: quux = new Bar(); break; case 2: quux = new Baz(); break; } Which invocation is more acceptable? Dictionary, for faster lookups and fewer keywords (case and break) Switch: More commonly found in code, doesn't require the use of a Func< object for indirection.

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• Canonical representation of a class object containing a list element in XML

  - by dendini

  I see that most implementations of JAX-RS represent a class object containing a list of elements as follows (assume a class House containing a list of People) <houses> <house> <person> <name>Adam</name> </person> <person> <name>Blake</name> </person> </house> <house> </house> </houses> The result above is obtained for instance from Jersey 2 JAX-RS implementation, notice Jersey creates a wrapper class "houses" around each house, however strangely it doesn't create a wrapper class around each person! I don't feel this is a correct mapping of a list, in other words I'd feel more confortable with something like this: <houses> <house> <persons> <person> <name>Adam</name> </person> <person> <name>Blake</name> </person> </persons> </house> <house> </house> </houses> Is there any document explaining how an object should be correctly mapped apart from any opninion?

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• Explicitly pass context object versus injecting with IoC

  - by SonOfPirate

  I have a layered service application where the service layer delegates operations into the domain layer for execution. Many of these operations need to know the context under which they are operation. (The context included the identity of the current user, culture information, etc. received from the caller.) For example, I have an API method that returns a list of announcements. The list is based on the current user's role and each announcement is localized to their culture. The API is a thin-facade that delegates to an Application Service in my domain layer. The Application Service method obviously needs to know the context of the current request/operation as another call to the same API from another user should result in a different list. Within this method, we also have logging that uses some of the context information so we a clear understanding of the context when the operation was performed (this is especially useful if something goes wrong.) While this is a contrived example, in the real world, my Application Services will coordinate operations with many collaborative components, any number of them also needing the context information. My choice is to pass the context to the Application Service which would then pass it with any calls to collaborators or have the IoC container satisfy the dependency the Application Service and any collaborators have on the context. I am wondering if it is considered good/bad, best practices/code smell, etc. if I pass the context object as a parameter to the domain methods or if injecting the context via an IoC container is preferred. (EDIT: I should mention that the context object is instantiated per-request.)

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