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• Designing a "Grid" like object that contains game objects

  - by liortal

  I am working on a 2D game, where there's a game "board" on which other game objects are placed. This this is 2D, my starting point was to design a class that will internally use a 2d array for the actual stored game objects. This class could be simply accessed by 2 indices: (i, j) to get game objects on it. My problem is that i have no idea how to make the game "board" "propagate" its data onto its children. Design questions i ran into are: Should the children placed on the board have display properties such as size, screen position? Should the board itself dictate this information? How to update children in case the board changes some of its properties? (position, etc). Should the board be aware of the types of objects stored in it ? I have no idea how similar things such as WPF or other UI frameworks go about organizing a "container like" object that can arrange or apply certain UI properties to its children.

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• How to handle status columns in designing tables

  - by altsyset

  How to handle multiple statuses for a table entry, for example an item table may have an active, inactive, fast moving, and/or batch statuses. And I wanted to handle them in single column with VARCHAR type. Also I might set each of those attributes as a boolean with different columns. But I am not sure what consequences this might lead to. So if you have experienced such situations which one would be the best way to handle it?

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• How to verify the Liskov substitution principle in an inheritance hierarchy?

  - by Songo

  Inspired by this answer: Liskov Substitution Principle requires that Preconditions cannot be strengthened in a subtype. Postconditions cannot be weakened in a subtype. Invariants of the supertype must be preserved in a subtype. History constraint (the "history rule"). Objects are regarded as being modifiable only through their methods (encapsulation). Since subtypes may introduce methods that are not present in the supertype, the introduction of these methods may allow state changes in the subtype that are not permissible in the supertype. The history constraint prohibits this. I was hoping if someone would post a class hierarchy that violates these 4 points and how to solve them accordingly. I'm looking for an elaborate explanation for educational purposes on how to identify each of the 4 points in the hierarchy and the best way to fix it. Note: I was hoping to post a code sample for people to work on, but the question itself is about how to identify the faulty hierarchies :)

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• Ruby - when to use instance variables vs parameters between methods?

  - by Michael Durrant

  I'm writing several methods that call other methods. To pass the information I have a couple of choices: Pass the information as parameters Set instance variables so that other methods can access them When should I choose one option over the other? It seems that the first option is good as it is very specific about what is being passed. the downside seems to be that a lot of values are being passed around. The second method doesn't require passing all the values around but seems to lead to a lot of magic where methods set instance variables 'somewhere' Should I always be very explicit about gets passed to other methods in the class? Are there exceptions so this?

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• Learning OO for a C Programmer

  - by Holysmoke

  I've been programming professionally in C, and only C, for around 10 years in a variety of roles. As would be normal to expect, I understand the idioms of the language fairly well and beyond that also some of the design nuances - which APIs to make public, who calls what, who does what, what is supposed to reentrant and so on. I grew up reading 'Writing Solid Code', it's early C edition, not the one based on C++. However, I've never ever programmed in an OO language. Now, I want to migrate to writing applications for iPhone (maybe android), so want to learn to use Objective-C and use it with a degree of competence fitting a professional programmer. How do I wrap my head around the OO stuff? What would be your smallest reading list suggestion to me. Is there a book that carries some sort of relatively real world example OO design Objective-C? Besides, the reading what source code would you recommend me to go through. How to learn OO paradigm using Objective-C?

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• how should I design Objects around this business requirement?

  - by brainydexter

  This is the business requirement: " A Holiday Package (e.g. New York NY Holiday Package) can be offered in different ways based on the Origin city: From New Delhi to NY From Bombay to NY NY itself ( Land package ) (Bold implies default selection) a. and b. User can fly from either New Delhi or Bombay to NY. c. NY is a Land package, where a user can reach NY by himself and is a standalone holidayPackage. " Let's say I have a class that represents HolidayPackage, Destination (aka City). public class HolidayPackage{ Destination holidayCity; ArrayList<BaseHolidayPackageVariant> variants; BaseHolidayPackageVariant defaultVariant; } public abstract class BaseHolidayPackageVariant { private Integer variantId; private HolidayPackage holidayPackage; private String holidayPackageType; } public class LandHolidayPackageVariant extends BaseHolidayPackageVariant{ } public class FlightHolidayPackageVariant extends BaseHolidayPackageVariant{ private Destination originCity; } What data structure/objects should I design to support: options a default within those options Sidenote: A HolidayPackage can also be offered in different ways based on Hotel selections. I'd like to follow a design which I can leverage to support that use case in the future. This is the backend design I have in mind.

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• Is having 'Util' classes a cause for concern? [closed]

  - by Matt Fenwick

  I sometimes create 'Util' classes which primarily serve to hold methods and values that don't really seem to belong elsewhere. But every time I create one of these classes, I think "uh-oh, I'm gonna regret this later ...", because I read somewhere that it's bad. But on the other hand, there seem to be two compelling (at least for me) cases for them: implementation secrets that are used in multiple classes within a package providing useful functionality to augment a class, without cluttering its interface Am I on the way to destruction? What you say !! Should I refactor?

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• Setting up ASP.NET structure for code

  - by user1175327

  I've always coded in C# MVC3 when developing web applications. But now i wanted to learn a bit more about developing web sites with just ASP.NET. But now i'm wondering what a good setup for my code would be. For me, an MVC like pattern seems to be a good way to go. But obviously ASP.NET doesn't have any router and controller classes. So i guess people have a different way of setting up their code when they do ASP.NET. So i'm looking for more information on how to get started with this. So not really the basics of ASP.NET, but something that focuses on a good code setup. Any good tutorials/information about this/?

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• Oracle NoSQL Database Using FusionIO ioDrive2

  - by Charles Lamb

  We ran some benchmarks using FusionIO ioDrive2 SSD drives and Oracle NoSQL Database. FusionIO has published a whitepaper with the results of the benchmarks. "Results of testing showed that using an ioDrive2 for data delivered nearly 30 times more operations per second than a 300GB 10k SAS disk on a 90 percent read and 10 percent write workload and nearly eight times more operations per second on a 50 percent read and 50 percent write workload. Equally impressive, an ioDrive2 reduced latency over 700 percent (seven times) on inserts in a 90 percent read and 10 percent write workload and over 5800 percent (58 times) on reads in a 50 percent read and 50 percent write workload."

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• Breaking up classes and methods into smaller units

  - by micahhoover

  During code reviews a couple devs have recommended I break up my methods into smaller methods. Their justification was (1) increased readability and (2) the back trace that comes back from production showing the method name is more specific to the line of code that failed. There may have also been some colorful words about functional programming. Additionally I think I may have failed an interview a while back because I didn't give an acceptable answer about when to break things up. My inclination is that when I see a bunch of methods in a class or across a bunch of files, it isn't clear to me how they flow together, and how many times each one gets called. I don't really have a good feel for the linearity of it as quickly just by eye-balling it. The other thing is a lot of people seem to place a premium of organization over content (e.g. 'Look at how organized my sock drawer is!' Me: 'Overall, I think I can get to my socks faster if you count the time it took to organize them'). Our business requirements are not very stable. I'm afraid that if the classes/methods are very granular it will take longer to refactor to requirement changes. I'm not sure how much of a factor this should be. Anyway, computer science is part art / part science, but I'm not sure how much this applies to this issue.

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• Cookie access within a HTTP Class

  - by James Jeffery

  I have a HTTP class that has a Get, and Post, method. It's a simple class I created to encapsulate Post and Get requests so I don't have to repeat the get/post code throughout the application. In C#: class HTTP { private CookieContainer cookieJar; private String userAgent = "..."; public HTTP() { this.cookieJar = new CookieContainer(); } public String get(String url) { // Make get request. Return the JSON } public String post(String url, String postData) { // Make post request. Return the JSON } } I've made the CookieJar a property because I want to preserve the cookie values throughout the session. If the user is logged into Twitter with my application, each request I make (be it get or post) I want to use the cookies so they remain logged in. That's the basics of it anyway. But, I don't want to return a string in all instances. Sometimes I may want the cookie, or a header value, or something else from the request. Ideally I'd like to be able to do this in my code: Cookie cookie = http.get("http://google.com").cookie("g_user"); String g_user = cookie.value; or String source = http.get("http://google.com").body; My question - To do this, would I need to have a Get class, and a Post class, that are included within the HTTP class and are accessible via accessors? Within the Get and Post class I would then have the Cookie method, and the body property, and whatever else is needed. Should I also use an interface, or create a Request class and have Post and Get extend it so that common methods and properties are available to both classes? Or, am I thinking totally wrong?

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• To identify the classes for uml diagrams?

  - by user106535

  I want to implement a software engineering project based on "crime management system". The main modules are: visitors, users, administrator. The main events that are taking place are: registration, report complaint, report crime, report most wanted, view status of reported crime. So could you please help me to identify the classes that are to be used in this project and help me to draw the class diagram?

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• Why setter method when getter method enough in PHP OOP

  - by phphunger

  I am practicing OOP with PHP, and I am struck at setter and getter methods. I can directly access the class properties and methods with getter method then what's the use of setter method? See my example. <?php class MyClass{ public $classVar = "Its a class variable"; public function Getter(){ return $this -> classVar; } } $obj = new MyClass; echo $obj -> Getter(); ?>

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• Semantic coupling vs. large class

  - by user106587

  I have hardware I communicate with via TCP. This hardware accepts ~40 different commands/requests with about 20 different responses. I've created a HardwareProxy class which has a TcpClient to send and receive data. I didn't like the idea of having 40 different methods to send the commands/requests, so I started down the path of having a single SendCommand method which takes an ICommand and returns an IResponse, this results in 40 different SpecificCommand classes. The problem is this requires semantic coupling, i.e. the method that invokes SendCommand receives an IResponse which it has to downcast to SpecificResponse, I use a future map which I believe ensures the appropriate SpecificResponse, but I get the impression this code smells. Besides the semantic coupling, ICommand and IResponse are essentially empty abstract classes (Marker Interfaces) and this seems suspicious to me. If I go with the 40 methods I don't think I have broken the single responisbility principle as the responsibility of the HardwareProxy class is to act as the hardware, which has all of these commands. This route is just ugly, plus I'd like to have Asynchronous versions, so there'd be about 80 methods. Is it better to bite the bullet and have a large class, accept the coupling and MarkerInterfaces for a smaller soultuion, or am I missing a better way? Thanks.

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• Exchange 2007 - Mailbox Database Recovery

  - by Phrontiste

  Exchange 2007 edb Can we restore Exchange edb (First storage group\mailbox database.edb) to another exchange server ? Do I just copy the edb to the new exchange server and delete the first storage group\mailbox database.edb and replace it with this one ? How can I get all the mailboxes from that (old) mailbox database.edb ? I had a exchange 2007 server with 10 mailboxes, I have installed exchange on another machine and was thinking if I can do the above ? or is there any way I can get all the mailboxes from that edb (old mailbox database) and import them into the new one. I have deleted the old exchange install I had (these are test machines) What are the steps required to get the DB working on the new machine ? Also, I am confused about the recovery storage group ? I can mount a mailbox database in recovery storage group, but when I try to get mailbox out of it, it won't match any thing ? can someone please assist in understanding RSG and how to restore the OLD mailbox database. thanks and regards Phrontiste

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• correct way to implement auth/acl in mvc

  - by WiseStrawberry

  I am looking into making a correctly laid out MVC auth/acl system. I think I want the authentication of a user (and the session handling) to be seperate from the ACL system. (I don't know why but this seems a good idea from the things I've read) What does mvc have to do with this question you ask? Because I wish for the application to be well integrated with my acl. An example of a controller (CodeIgniter) <?php class forums extends MX_Controller { $allowed = array('users', 'admin'); $need_login = true; function __construct() { //example of checking if logged in. if($this->auth->logged_in() && $this->auth->is_admin()) { echo "you're logged in!"; } } public function add_topic() { if($this->auth->allowed('add_topic') { //some add topic things. } else { echo 'not allowed to add topic'; } } } ?> My thoughts $this->auth would be autoloaded in the system. I would like to check the $allowed array against the user currently (not) logged in and react accordingly. Is this a good way of doing things? I haven't seen much literature on mvc integration and auth. I want to make things as easy as possible.

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• Should all, none, or some overriden methods call Super?

  - by JoJo

  When designing a class, how do you decide when all overridden methods should call super or when none of the overridden methods should call super? Also, is it considered bad practice if your code logic requires a mixture of supered and non-supered methods like the Javascript example below? ChildClass = new Class.create(ParentClass, { /** * @Override */ initialize: function($super) { $super(); this.foo = 99; }, /** * @Override */ methodOne: function($super) { $super(); this.foo++; }, /** * @Override */ methodTwo: function($super) { this.foo--; } }); After delving into the iPhone and Android SDKs, I noticed that super must be called on every overridden method, or else the program will crash because something wouldn't get initialized. When deriving from a template/delegate, none of the methods are supered (obviously). So what exactly are these "je ne sais quoi" qualities that determine whether a all, none, or some overriden methods should call super?

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• Are injectable classes allowed to have constructor parameters in DI?

  - by Songo

  Given the following code: class ClientClass{ public function print(){ //some code to calculate $inputString $parser= new Parser($inputString); $result= $parser->parse(); } } class Parser{ private $inputString; public __construct($inputString){ $this->inputString=$inputString; } public function parse(){ //some code } } Now the ClientClass has dependency on class Parser. However, if I wanted to use Dependency Injection for unit testing it would cause a problem because now I can't send the input string to the parser constructor like before as its calculated inside ClientCalss itself: class ClientClass{ private $parser; public __construct(Parser $parser){ $this->parser=$parser; } public function print(){ //some code to calculate $inputString $result= $this->parser->parse(); //--> will throw an exception since no string was provided } } The only solution I found was to modify all my classes that took parameters in their constructors to utilize Setters instead (example: setInputString()). However, I think there might be a better solution than this because sometimes modifying existing classes can cause much harm than benefit. So, Are injectable classes not allowed to have input parameters? If a class must take input parameters in its constructor, what would be the way to inject it properly? UPDATE Just for clarification, the problem happens when in my production code I decide to do this: $clientClass= new ClientClass(new Parser($inputString));//--->I have no way to predict $inputString as it is calculated inside `ClientClass` itself. UPDATE 2 Again for clarification, I'm trying to find a general solution to the problem not for this example code only because some of my classes have 2, 3 or 4 parameters in their constructors not only one.

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• Does FP mess up your OOP skills?

  - by bonomo

  I've been learning functional programming in Haskell and F# for awhile and now when I got some skills it gets harder for me to think in OOP way and program in C# and JavaScript. Everything seems to be ass-backwards there with classes, interfaces, objects and I often stare at the screen trying to think of a better way around without using them. This is something that scares me, because I didn't have problems like that before (not knowing that the same stuff can be done in a different way). So I am concerned as I don't want to loose myself as a OOP developer, because this is what I do for living. Is it a normal thing? Shall I rather stop doing FP? How did you manage to cope with it?

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• Class Versus Struct

  - by Prometheus87

  In C++ and other influenced languages there is a construct called Structure (struct) and we all know the class. Both are capable of holding functions and variables. some differences are 1. Class is given memory in heap and struct is given memory in stack 2. in class variable are private by default and in struct thy are public My question is that struct was somehow abandoned for Class. Why? other that abstraction, a struct can do all the same stuff a class does. Then why abandon it?

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• Python simulation-scripts architecture

  - by Beastcraft

  Situation: I've some scripts that simulate user-activity on desktop. Therefore I've defined a few cases (workflows) and implemented them in Python. I've also written some classes for interacting with the users' software (e.g. web browser etc.). Problem: I'm a total beginner in software design / architecture (coding isn't a problem). How could I structure what I described above? Providing a library which contains all the workflows as functions, or a separate class/module etc. for each workflow? I want to keep the the workflows simple. The complexity should be hidden in the classes for interacting with the users' software. Are there any papers / books I could read about this, or could you provide some tips? Kind regards, B

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• overriding implemented base class methods

  - by user793468

  I read somewhere that the chain of inheritance breaks when you alter a behavior from derived class. What does "altering a behavior" mean here? Is overriding an already implemented method in base class considered as "altering behavior"? Or, does the author mean altering method signatures and the output? Also, I ready Duplicating code is not a good practice, and its a maintenance nightmare. Again, does overriding an already implemented method in base class considered "Duplicating code"? If not, what would be considered as "Duplicating code"? I

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• PHP OOP: Am i following right way?

  - by sineverba

  I'm learning OOP (PHP). I've realized my own CRUD Class, that performs some kind of queries SQL. Btw, a Gasoline asked us to realize a smart, simple web-app where he can update prices of his gasoline (gasoline, diesel, lpg) and via an API i could recall them and display in his site. So, I did create a new Class Gasoline but it perform some methods of CRUD Class public function getPrezzoBenzina($id) { $prezzo_benzina = $this->distributore->sql('SELECT prezzo_benzina FROM prezzi WHERE id = '.$id); return $prezzo_benzina } And so on (code is pseudocode, just to explain). I could perform all my code only with help of Crud Class... without necessity of Class Gasoline. So, what I'm missing about OOP? Where am I wrong?

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• Read an object from compressed file generated from ActionScript 3

  - by Last Chance

  I have made a simple game Map Editor and I want to save a array that contain map tile info to a file, as below: var arr:Array = [.....2d tile info in it...]; var ba:ByteArray = new ByteArray(); ba.writeObject(arr); ba.compress(); var file:File = new File(); file.save(ba); I had successfully saved a compressed object to a file. Now the problem is my server side need to read this file and decompress the array out from the file, then convert it to a Python list. Is that possible?

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• DbNetSuite 4.2 released with integrated database charting

  DbNetLink is pleased to announce the release of DbNetSuite 4.2. DbNetSuite is a set of lightweight integrated AJAX enabled ASP.NET components for creating web applications that interface with the database and file systems. New in 4.2 "Out of the box" integration with MS Chart Control Save runtime user configuration with User Profiles Improved performance   Visit the web site for further information, online demos and a fully functional evaluation download. http://www.dbnetsuite.com...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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