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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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• is 'protected' ever reasonable outside of virtual methods and destructors?

  - by notallama

  so, suppose you have some fields and methods marked protected (non-virtual). presumably, you did this because you didn't mark them public because you don't want some nincompoop to accidentally call them in the wrong order or pass in invalid parameters, or you don't want people to rely on behaviour that you're going to change later. so, why is it okay for that nincompoop to use those fields and methods from a subclass? as far as i can tell, they can still screw up in the same ways, and the same compatibility issues still exist if you change the implementation. the cases for protected i can think of are: non-virtual destructors, so you can't break things by deleting the base class. virtual methods, so you can override 'private' methods called by the base class. constructors in c++. in java/c# marking the class as abstract will do basically the same. any other use cases?

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• Dump an arbitrary object To Html String

  - by Michael Freidgeim

  For debugging purposes me and my collegue wanted to dump details of the arbitrary object, and created function that uses LINQPad Dump functionality (thanks to http://stackoverflow.com/a/6035014/52277 and original http://linqpad.uservoice.com/forums/18302-linqpad-feature-suggestions/suggestions/447166-make-dump-extension-method-available-in-visual-s discussion)    public static string DumpToHtmlString<T>(this T objectToSerialize)        {            string strHTML = "";            try            {                var writer = LINQPad.Util.CreateXhtmlWriter(true);                writer.Write(objectToSerialize);                strHTML = writer.ToString();            }            catch (Exception exc)            {                Debug.Assert(false, "Investigate why ?" + exc);            }            return strHTML;        }You will need to add the linqpad executable as a reference in your project.TO DO similar in plain text ,look at https://github.com/ServiceStack/ServiceStack.Text StringExtensions , e.g. JsonSerializer/CsvSerializer or http://objectdumper.codeplex.com/

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• Subscribe/Publish Model in Web-based Application (c#) - Best Practices for Event Handlers

  - by KingOfHypocrites

  I was recently exposed to a desktop application that uses an publish/subscribe model to handle commands, events, etc. I can't seem to find any good examples of using this in a web application, so I wonder if I am off base in trying to use this for web based development (on the server side)? I'm using asp.net c#. My main question in regards to the design is: When using a publish/subscribe model, is it better to have generic commands/events that pass no parameters and then have the subscribers look at static context objects that contain the data relevant to the event? Or is it better to create custom arguments for every event that contain data related to the event? The whole concept of a global container seems so convenient but at the same time seems to break encapsulation. Any thoughts or best practices from anyone who has implemented this type of model in a web based application? Even suggestions on this model out of the scope of my question are appreciated.

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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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• Figuring out the Call chain

  - by BDotA

  Let's say I have an assemblyA that has a method which creates an instance of assemblyB and calls its MethodFoo(). Now assemblyB also creates an instance of assemblyC and calls MethodFoo(). So no matter if I start with assemblyB in the code flow or with assemlyA, at the end we are calling that MethodFoo of AssemblyC(). My question is when I am in the MethodFoo() how can I know who has called me? Has it been a call originally from assemblyA or was it from assemlyB? Is there any design pattern or a good OO way of solving this?

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• Is avoiding the private access specifier in PHP justified?

  - by Tifa

  I come from a Java background and I have been working with PHP for almost a year now. I have worked with WordPress, Zend and currently I'm using CakePHP. I was going through Cake's lib and I couldn't help notice that Cake goes a long way avoiding the "private" access specifier. Cake says Try to avoid private methods or variables, though, in favor of protected ones. The latter can be accessed or modified by subclasses, whereas private ones prevent extension or re-use. in this tutorial. Why does Cake overly shun the "private" access specifier while good OO design encourages its use i.e to apply the most restrictive visibility for a class member that is not intended to be part of its exported API? I'm willing to believe that "private" functions are difficult test, but is rest of the convention justified outside Cake? or perhaps it's just a Cake convention of OO design geared towards extensibility at the expense of being a stickler for stringent (or traditional?) OO design?

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• read object from compressed file that generate from actionscript3

  - 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); now I had successful save a compressed object to a file. now the problem is my server side need to read this file and decompress get the arr out from file, then convert it as python list. is that prossible?

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• Class design for calling "the same method" on different classes from one place

  - by betatester07

  Let me introduce my situation: I have Java EE application and in one package, I want to have classes which will act primarily as cache for some data from database, for example: class that will hold all articles for our website class that will hold all categories etc. Every class should have some update() method, which will update data for that class from database and also some other methods for data manipulation specific for that data type. Now, I would like to call update() method for all class instances (there will be exactly one class instance for every class) from one place. What is the best design?

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• Clarify the Single Responsibility Principle.

  - by dsimcha

  The Single Responsibility Principle states that a class should do one and only one thing. Some cases are pretty clear cut. Others, though, are difficult because what looks like "one thing" when viewed at a given level of abstraction may be multiple things when viewed at a lower level. I also fear that if the Single Responsibility Principle is honored at the lower levels, excessively decoupled, verbose ravioli code, where more lines are spent creating tiny classes for everything and plumbing information around than actually solving the problem at hand, can result. How would you describe what "one thing" means? What are some concrete signs that a class really does more than "one thing"?

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• Structuring cascading properties - parent only or parent + entire child graph?

  - by SB2055

  I have a Folder entity that can be Moderated by users. Folders can contain other folders. So I may have a structure like this: Folder 1 Folder 2 Folder 3 Folder 4 I have to decide how to implement Moderation for this entity. I've come up with two options: Option 1 When the user is given moderation privileges to Folder 1, define a moderator relationship between Folder 1 and User 1. No other relationships are added to the db. To determine if the user can moderate Folder 3, I check and see if User 1 is the moderator of any parent folders. This seems to alleviate some of the complexity of handling updates / moved entities / additions under Folder 1 after the relationship has been defined, and reverting the relationship means I only have to deal with one entity. Option 2 When the user is given moderation privileges to Folder 1, define a new relationship between User 1 and Folder 1, and all child entities down to the grandest of grandchildren when the relationship is created, and if it's ever removed, iterate back down the graph to remove the relationship. If I add something under Folder 2 after this relationship has been made, I just copy all Moderators into the new Entity. But when I need to show only the top-level Folders that a user is Moderating, I need to query all folders that have a parent folder that the user does not moderate, as opposed to option 1, where I just query any items that the user is moderating. I think it comes down to determining if users will be querying for all parent items more than they'll be querying child items... if so, then option 1 seems better. But I'm not sure. Is either approach better than the other? Why? Or is there another approach that's better than both? I'm using Entity Framework in case it matters.

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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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• Is wrapping a third party code the only solution to unit test its consumers? [closed]

  - 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. Now some people argue that if a library is stable enough and won't change often then there is no need to wrap it. So assuming that Zend_Mail is stable and won't change and it fits my needs entirely, then I won't need a wrapper for it. Now take a look at my class Logger that depends on Zend_Mail: 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. Now is wrapping Zend_Mail the only solution or is there a better approach to this problem? 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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• Is it wrong to use a boolean parameter to determine behavior?

  - by Ray

  I have seen a practice from time to time that "feels" wrong, but I can't quite articulate what is wrong about it. Or maybe it's just my prejudice. Here goes: A developer defines a method with a boolean as one of its parameters, and that method calls another, and so on, and eventually that boolean is used, solely to determine whether or not to take a certain action. This might be used, for example, to allow the action only if the user has certain rights, or perhaps if we are (or aren't) in test mode or batch mode or live mode, or perhaps only when the system is in a certain state. Well there is always another way to do it, whether by querying when it is time to take the action (rather than passing the parameter), or by having multiple versions of the method, or multiple implementations of the class, etc. My question isn't so much how to improve this, but rather whether or not it really is wrong (as I suspect), and if it is, what is wrong about it.

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• Rotate object Up/Down/Left/Right in any orientation

  - by George Duckett

  I'm rendering model at the origin with a fixed camera looking at it positioned on the z axis. I want to be able to rotate the model up/down and left/right. Currently I have 2 variables, HorizontalRotation and VerticalRotation. When calculating the world matrix I rotate about the Y axis by HorizontalRotation and about the X axis by VerticalRotation. The ..Rotation variables are controlled by pressing up/down/left/right arrow keys. The problem I'm having is that the rotations are happening relative to the object. Lets say it's a model of the world. Pressing Up a bit would let me look at the north pole. Currently when i press right the earth spins infront of the camera on its axis; I'm still looking at the north pole. How can i get it so that no matter what rotations are currently applied i can always rotate my model relative to the camera/world axis?

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• Finding the best practice for a game simulating tool

  - by Tougheart

  I'm studying Java right now, and I'm thinking of this tool as my practice project. The game is "League of Legends" in case anyone knows it, I'm not actually simulating the game as in simulating game play, I'm just trying to create a tool that can compare different champions to each other based on their own abilities and items bought inside the game. The game basics are: Every player has a champion in a team of 5 players playing against another team. Each champion has a different set of abilities (usually 4) that s/he uses to do damage to opposing champions. Each champion gets stronger by buying different items, increasing the attack it deals or decreasing the damage received. What I want to do is to create a tool to be used outside the game enabling players to try out different builds for their champions and compare the figures against other champions they usually fight against. The goal is to enable players get a deeper understanding of the different item combinations (builds) that can be used during the games, instead of trying them out in real games which can be somehow very time consuming. What I'm stuck at is the best practice I should follow to make this possible using Java, I can't figure out which classes should inherit from which, should I make champions and items specs in the code or extracted from other files, specially that I'm talking about hundreds of items and champions to use in that tool. I'm self studying Java, and I don't have much practice at it, so I would really appreciate any broad guidelines regarding this, and sorry if my question doesn't fit here, I tried to follow the rules. English isn't my native language, so I'm really sorry if I wasn't clear enough, I would be more than happy to explain anything that's not understood.

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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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• Non-object-oriented game tutorials

  - by Arcadian

  I've been tasked with writing an essay extolling the virtues of object oriented programming and creating an accompanying game to demonstrate them. My initial idea is to find a tutorial for a simple game written in a programming language which does not follow the OOP paradigm (or written in an OOP language but not in an OOP way) and recreate it in an OOP way using either C# or Java (haven't yet decided). This would then allow me to make concrete comparisons between the two. The game doesn't have to be anything complex; Tetris, Pong, etc. that sort of thing. The problem I've had so far is finding a suitable tutorial, any suggestions?

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• Instantiating objects in Java

  - by Davis Naglis

  I'm learning now Java from scratch and when I started to learn about instantiating objects, I don't understand - in which cases do I need to instantiate objects? For example I'm studying from TutsPlus course about it and there is example about "Rectangle" class. Instructor says that it needs to be instantiated. So I started to doubt about - when do I need to instantiate those objects when writing Java code?

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• What is the order of diagram drawing in a design?

  - by Manuel Malagon

  I'm new with OOP and UML and I have some confusion here. I'd like to know where to start, I mean, somebody comes to you and ask you to do something (involves software design of course), once you have determined what has to be done, what is the order in which you have to start the software architecture? I mean, is it first the use case diagram or the class diagram? or should I draw some diagrams in parallel? But basically, where should I start? and what UML diagram goes first? Thanks for helping!!

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• How can I design my classes for a calendar based on database events?

  - by Gianluca78

  I'm developing a web calendar in php (using Symfony2) inspired by iCal for a project of mine. At this moment, I have two classes: a class "Calendar" and a class "CalendarCell". Here you are the two classes properties and method declarations. class Calendar { private $month; private $monthName; private $year; private $calendarCellList = array(); private $translator; public function __construct($month, $year, $translator) {} public function getCalendarCells() {} public function getMonth() {} public function getMonthName() {} public function getNextMonth() {} public function getNextYear() {} public function getPreviousMonth() {} public function getPreviousYear() {} public function getYear() {} private function calculateDaysPreviousMonth() {} private function calculateNumericDayOfTheFirstDayOfTheWeek() {} private function isCurrentDay(\DateTime $dateTime) {} private function isDifferentMonth(\DateTime $dateTime) {} } class CalendarCell { private $day; private $month; private $dayNameAbbreviation; private $numericDayOfTheWeek; private $isCurrentDay; private $isDifferentMonth; private $translator; public function __construct(array $parameters) {} public function getDay() {} public function getMonth() {} public function getDayNameAbbreviation() {} public function isCurrentDay() {} public function isDifferentMonth() {} } Each calendar day can includes many events stored in a database. My question is: which is the best way to manage these events in my classes? I think to add a eventList property in CalendarCell and populate it with an array of CalendarEvent objects fetched by the database. This kind of solution doesn't allow other coders to reuse the classes without db (because I should inject at least a repository services also) just to create and visualize a calendar... so maybe it could be better to extend CalendarCell (for instance in CalendarCellEvent) and add the database features? I feel like I'm missing some crucial design pattern! Any suggestion will be very appreciated!

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• Am I violating LSP if the condition can be checked?

  - by William

  This base class for some shapes I have in my game looks like this. Some of the shapes can be resized, some of them can not. private Shape shape; public virtual void SetSizeOfShape(int x, int y) { if (CanResize()){ shape.Width = x; shape.Height = y; } else { throw new Exception("You cannot resize this shape"); } } public virtual bool CanResize() { return true; } In a sub class of a shape that I don't ever want to resize I am overriding the CanResize() method so a piece of client code can check before calling the SetSizeOfShape() method. public override bool CanResize() { return false; } Here's how it might look in my client code: public void DoSomething(Shape s) { if(s.CanResize()){ s.SetSizeOfShape(50, 70); } } Is this violating LSP?

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• should singleton be life-time available or should it be destroyable?

  - by Manoj R

  Should the singleton be designed so that it can be created and destroyed at any time in program or should it be created so that it is available in life-time of program. Which one is best practice? What are the advantages and disadvantages of both? EDIT :- As per the link shared by Mat, the singleton should be static. But then what are the disadvantages of making it destroyable? One advantage is it memory can be saved when it is not useful.

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• Computer Engineer in CS Interview

  - by blasteye

  As a Computer Engineering student, while in school I've primarily dealt with C, Matlab, and VHDL. On my own though, i learned a bit about OOP (Polymorphism, inheritance, encapsulation), and have done quite a bit of web development using JavaScript/PHP/Node.js While at coding interviews I've be asked academia CS questions such as "abstract vs interface". The problem is that I didn't know the official terminology, but I have dealt with this type of programming decisions/concepts. Could anyone recommend a good resource for me to learn these academia CS terms?

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• Advantages to Multiple Methods over Switch

  - by tandu

  I received a code review from a senior developer today asking "By the way, what is your objection to dispatching functions by way of a switch statement?" I have read in many places about how pumping an argument through switch to call methods is bad OOP, not as extensible, etc. However, I can't really come up with a definitive answer for him. I would like to settle this for myself once and for all. Here are our competing code suggestions (php used as an example, but can apply more universally): class Switch { public function go($arg) { switch ($arg) { case "one": echo "one\n"; break; case "two": echo "two\n"; break; case "three": echo "three\n"; break; default: throw new Exception("Unknown call: $arg"); break; } } } class Oop { public function go_one() { echo "one\n"; } public function go_two() { echo "two\n"; } public function go_three() { echo "three\n"; } public function __call($_, $__) { throw new Exception("Unknown call $_ with arguments: " . print_r($__, true)); } } Part of his argument was "It (switch method) has a much cleaner way of handling default cases than what you have in the generic __call() magic method." I disagree about the cleanliness and in fact prefer call, but I would like to hear what others have to say. Arguments I can come up with in support of Oop scheme: A bit cleaner in terms of the code you have to write (less, easier to read, less keywords to consider) Not all actions delegated to a single method. Not much difference in execution here, but at least the text is more compartmentalized. In the same vein, another method can be added anywhere in the class instead of a specific spot. Methods are namespaced, which is nice. Does not apply here, but consider a case where Switch::go() operated on a member rather than a parameter. You would have to change the member first, then call the method. For Oop you can call the methods independently at any time. Arguments I can come up with in support of Switch scheme: For the sake of argument, cleaner method of dealing with a default (unknown) request Seems less magical, which might make unfamiliar developers feel more comfortable Anyone have anything to add for either side? I'd like to have a good answer for him.

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