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  • Switching from abstract class to interface

    - by nischayn22
    I have an abstract class which has all abstract methods except one which constructs objects of the subclasses. Now my mentor asked me to move this abstract class to an interface. Having an interface is no problem except with the method used to construct subclass objects. Where should this method go now? Also, I read somewhere that interfaces are more efficient than abstract classes. Is this true? Here's an example of my classes abstract class Animal { //many abstract methods getAnimalobject(some parameter) { return //appropriate subclass } } class Dog extends Animal {} class Elephant extends Animal {}

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  • Class as first-class object

    - by mrpyo
    Could a class be a first-class object? If yes, how would the implementation look? I mean, how could syntax for dynamically creating new classes look like? EDIT: I mean what example syntax could look like (I'm sorry, English is not my native language), but still I believe this question makes sense - how you give this functionality while keeping language consistent. For example how you create reference for new type. Do you make reference first-class object too and then use something like this: Reference<newType> r = new Reference<newType>(); r.set(value); Well this could get messy so you may just force user to use Object type references for dynamically created classes, but then you loose type-checking. I think creating concise syntax for this is interesting problem which solving could lead to better language design, maybe language which is metalanguage for itself (I wonder if this is possible).

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  • Which programming career path fits my terms? [closed]

    - by Goward Gerald
    I am sick and tired of my enterprise development job, I need some programming direction like this: Demanded in jobs-market Demanded in freelance market Can use Ubuntu as development environment Not enterprise. Standalone, mobile, web-development, anything, just not enterprise. Basically, I need a programming direction which doesn't need 20 developers, terribly big databases systems and long going projects with intense long-term support, I don't want enterprise job where a lot of people are working on one terribly big project and do modules to it all day long. Instead, I need something where: Projects change pretty often Projects are little, or medium-sized (in terms of code, modules and people working on it) but still not enterprise-sized Possible for freelance, solo-development, or at least requires a team of 3-4 programmers. Not like in enterprise where you feel like a drop in the sea with your 50 classes while system itself has hundreds of classes. Suggestions please?

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  • How to make the switch to C++11?

    - by Overv
    I've been programming in C++ for a while now, but mostly thinks centered around the low-level features of C++. By that I mean mostly working with pointers and raw arrays. I think this behavior is known as using C++ as C with classes despite me only having tried C recently for the first time. I was pleasantly surprised how languages like C# and Java hide these details away in convenient standard library classes like Dictionaries and Lists. I'm aware that the C++ standard library has many convenience containers like vectors, maps and strings as well and C++11 only adds to this by having std:: array and ranged loops. How do I best learn to make use of these modern language features and which are suitable for which moments? Is it correct that software engineering in C++ nowadays I'd mostly free of manual memory management? Lastly, which compiler should I use to make the most of the new standard? Visual Studio has excellent debugging tools, but even VS2012 seems to have terrible C++11 support.

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  • Serious Forum Design Issue

    - by John
    I want to launch a school forum for a country. I'm in dilemma as to how to design this forum. Country will have many states, each state will have cities, each city will have many schools. Each school will have many classes( 1st - 12th). It looks like this: States - Cities - Schools - Classes I want to make each class as forum. Now the biggest problems are two fold: If I were to list even 1000 schools it will create huge number of forums and I don't think forum softwares(PHPBB, MyBB) are designed to support these many Secondly creating and maintaining huge forums is also very difficult. Ideally I'd like to duplicate existing forum hierarchy to new one. I've done lot of search and I've found that such type of forums are infeasible and such designs don't work. Leave alone the fact the nobody uses such a forum. Keeping in mind this, how should I go about designing this forum?

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  • Why should a class be anything other than "abstract" or "final/sealed"

    - by Nicolas Repiquet
    After 10+ years of java/c# programming, I find myself creating either: abstract classes: contract not meant to be instantiated as-is. final/sealed classes: implementation not meant to serve as base class to something else. I can't think of any situation where a simple "class" (i.e. neither abstract nor final/sealed) would be "wise programming". Why should a class be anything other than "abstract" or "final/sealed" ? EDIT This great article explains my concerns far better than I can.

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  • How to improve programming skills?

    - by Mike
    I'm very new to programming. I started learning PHP about half a year ago, so I do know something. I can write small functions, I can export and import information from a database and I can make a website. I don't know OOP principles and I don't know about objects and classes. Should I move to OOP principles and learn about classes, methods and objects? If not, what should I do? Continue writing simple code? How can a programmer write his/her own API? Is OOP necessary to do this? So how can i improve my skills? I love programming. I spend my 24/7 on it, so any help will be appreciated.

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  • When to use mixins in Ruby

    - by Gilles
    I am wondering when to use mixins? I have read about them. Many authors compare them to interfaces, abstract classes, etc. Mixins are modules that are mixed-in and modules are a way to group similar methods, constants and classes together. I have seen examples where a module for math functions is created. It makes sense to group and reuse such functions but should I only mix these in a class if I am faced with an inheritance situation? Should I mix these in anytime I want to use them in a class? Should they be used exactly like interfaces in other languages or are there other subtleties?

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  • What would the ultimate developer training class look like?

    - by user652273
    I think today's typical/traditional 3-5 days developer training classes aren't so great, as you tend to forget half of it shortly after. It's too much one way communication and not enough interaction. Also brain research has shown that this kind of setup is usually not optimal for efficient learning. For clarification, I am referring to professional, commercial, paid classes. However this could also be applied for any kind of studies. How could the ultimate developer training package be setup to really make sure you learn what you are supposed to learn? Would that be more: Multimedia? Exercises? Homeworks? Spread out over time instead of 3-5 compact days? Group projects?

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  • Creating classed in JavaScript

    - by Renso
    Goal:Creating class instances in JavaScript is not available since you define "classes" in js with object literals. In order to create classical classes like you would in c#, ruby, java, etc, with inheritance and instances.Rather than typical class definitions using object literals, js has a constructor function and the NEW operator that will allow you to new-up a class and optionally provide initial properties to initialize the new object with.The new operator changes the function's context and behavior of the return statement.var Person = function(name) {   this.name = name;};   //Init the personvar dude= new Person("renso");//Validate the instanceassert(dude instanceof Person);When a constructor function is called with the new keyword, the context changes from global window to a new and empty context specific to the instance; "this" will refer in this case to the "dude" context.Here is class pattern that you will need to define your own CLASS emulation library:var Class = function() {   var _class = function() {      this.init.apply(this, arguments);   };   _class.prototype.init = function(){};   return _class;}var Person a new Class();Person.prototype.init = function() {};var person = new Person;In order for the class emulator to support adding functions and properties to static classes as well as object instances of People, change the emulator:var Class = function() {   var _class = function() {      this.init.apply(this, arguments);   };   _class.prototype.init = function(){};   _class.fn = _class.prototype;   _class.fn.parent = _class;   //adding class properties   _class.extend = function(obj) {      var extended = obj.extended;      for(var i in obj) {         _class[i] = obj[i];      };      if(extended) extended(_class);   };   //adding new instances   _class.include = function(obj) {      var included = obj.included;      for(var i in obj) {         _class.fn[i] = obj[i];      };      if(included) included(_class);   };   return _class;}Now you can use it to create and extend your own object instances://adding static functions to the class Personvar Person = new Class();Person.extend({   find: function(name) {/*....*/},      delete: function(id) {/*....*/},});//calling static function findvar person = Person.find('renso');   //adding properties and functions to the class' prototype so that they are available on instances of the class Personvar Person = new Class;Person.extend({   save: function(name) {/*....*/},   delete: function(id) {/*....*/}});var dude = new Person;//calling instance functiondude.save('renso');

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  • Running a compiled Java program

    - by Roshan George
    I have a question on a compiled Java program that I have written. I have a Java file that has three classes defined within it. When I compiled the program I got a total of four classes. How do I make this into a form where I can run my application just by clicking an icon or something, or by issuing just a single command. For example, if I make it as an exe file, it could run only on Windows, how do I make it into a form compatible with all Oses. And hoe?

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  • What is a good design model for my new class?

    - by user66662
    I am a beginning programmer who, after trying to manage over 2000 lines of procedural php code, now has discovered the value of OOP. I have read a few books to get me up to speed on the beginning theory, but would like some advice on practical application. So,for example, let's say there are two types of content objects - an ad and a calendar event. what my application does is scan different websites (a predefined list), and, when it finds an ad or an event, it extracts the data and saves it to a database. All of my objects will share a $title and $description. However, the Ad object will have a $price and the Event object will have $startDate. Should I have two separate classes, one for each object? Should I have a 'superclass' with the $title and $description with two other Ad and Event classes with their own properties? The latter is at least the direction I am on now. My second question about this design is how to handle the logic that extracts the data for $title, $description, $price, and $date. For each website in my predefined list, there is a specific regex that returns the desired value for each property. Currently, I have an extremely large switch statement in my constructor which determines what website I am own, sets the regex variables accordingly, and continues on. Not only that, but now I have to repeat the logic to determine what site I am on in the constructor of each class. This doesn't feel right. Should I create another class Algorithms and store the logic there for each site? Should the functions of to handle that logic be in this class? or specific to the classes whos properties they set? I want to take into account in my design two things: 1) I will add different content objects in the future that share $title and $description, but will have their own properties, so, I want to be able to easily grow these as needed. 2) I will add more websites constantly (each with their own algorithms for data extraction) so I would like to plan efficienty managing and working with these now. I thought about extending the Ad or Event class with 'websiteX' class and store its functions there. But, this didn't feel right either as now I have to manage 100s of little website specific class files. Note, I didn't know if this was the correct site or stackoverflow was the better choice. If so, let me know and I'll post there.

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  • Alternative to "inheritance versus composition?" [closed]

    - by Frank
    Possible Duplicate: Where does this concept of “favor composition over inheritance” come from? I have colleagues at work who claim that "Inheritance is an anti-pattern" and want to use composition systematically instead, except in (rare, according to them) cases where inheritance is really the best way to go. I want to suggest an alternative where we continue using inheritance, but it is strictly forbidden (enforced by code reviews) to use anything but public members of base classes in derived classes. For a case where we don't need to swap components of a class at runtime (static inheritance), would that be equivalent enough to composition? Or am I forgetting some other important aspect of composition?

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  • Programming curricula

    - by davidk01
    There are a lot of schools that teach Java and C++ but whenever I see the syllabus for one of these classes it's almost always some cut and dry OO stuff with possibly some boring end of class project. With all the little gadgets and emulators for those gadgets why aren't more schools re-purposing those classes so that the students work their way up to building android or meego applications? That way students get to experience first hand what it takes to engineer/build a piece of software instead of doing finger exercises with syntax. Practically every self-taught programmer that I know started programming because they wanted to make their gadgets do things for them. They didn't learn a programming language with an abstract conception of using it on some far distant project so I don't understand why schools don't emulate this style of teaching.

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  • Map, Set use cases in a general web app

    - by user2541902
    I am currently working on my own Java web app (to be shown in interview to get a Java job). So I've not worked on Java in professional environment, so no guidance. I have database, entity classes, JPA relationships. Use cases are like, user has albums, album has pics, user has locations, location has co-ordinates etc. I used List (ArrayList) everywhere. I can do anything with List and DB, get some entry, find etc. For example, I will keep the list of users in List, then use queries to get some entry (why would I keep them in Map with id/email as key?). I know very well the working and features, implementing classes of Map, Set. I can use them for solving some algorithm, processing some data etc. In interviews, I get asked have you worked with these, where have you used them etc. So, Please tell me cases where they should be used (DB or any popular real use case).

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  • How to determine if class meets single responsibility principle ?

    - by user1483278
    Single Responsibility Principle is based on high cohesion principle. The difference between the two is that highly cohesive classes feature a set of responsibilities that are strongly related, while classes adhering to SRP have just one responsibility. But how do we determine whether particular class features a set of responsibilities and is thus just highly cohesive, or whether it has only one responsibility and is thus adhering to SRP? Namely, isn't it more or less subjective, since some may find class very granular ( and as such will consider a class as adhering to SRP ), while others may find it not granular enough?

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  • Fitting an established site into a CI framework

    - by David
    I manage a rather large, feature full nightmare of a site which has no end of feature creep settings/options/etc. Up to now its been coded in a procedural/functional way and would like to move to an OO,MVC setup. I'm quite new to it all but have done alot of research and feel that CodeIgniter is a code choice of framework to use to help quicken the transfer. Before looking at a framework, I started constructing a list of objects to create classes out of: photos users forum topics forums blogs blog posts comments The trouble I have now, is I do understand where these generic/universal objects fall into the CI MVC setup. What is the best way to organise this kind of stuff? These classes can generally be used on multiple models/views/controllers.

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  • Tip #19 Module Private Visibility in OSGi

    - by ByronNevins
    I hate public and protected methods and classes.  It requires so much work to change them in a huge project like GlassFish.  Not to mention that you may well have to support those APIs forever.  They are highly overused in GlassFish.  In fact I'd bet that > 95% of classes are marked as public for no good reason.  It's just (bad) habit is my guess. private and default visibility (I call it package-private) is easier to maintain.  It is much much easier to change such classes and methods around.  If you have ANY public method or public class in GlassFish you'll need to grep through a tremendous amount of source code to find all callers.  But even that won't be theoretically reliable.  What if a caller is using reflection to access public methods?  You may never find such usages. If you have package private methods, it's easy.  Simply grep through all the code in that one package.  As long as that package compiles ok you're all set.  There can' be any compile errors anywhere else.  It's a waste of time to even look around or build the "outside" world.  So you may be thinking: "Aha!  I'll just make my module have one giant package with all the java files.  Then I can use the default visibility and maintenance will be much easier.  But there's a problem.  You are wasting a very nice feature of java -- organizing code into separate packages.  It also makes the code much more encapsulated.  Unfortunately to share code between the packages you have no choice but to declare public visibility. What happens in practice is that a module ends up having tons of public classes and methods that are used exclusively inside the module.  Which finally brings me to the point of this blog:  If Only There Was A Module-Private Visibility Available Well, surprise!  There is such a mechanism.  If your project is running under OSGi that is.  Like GlassFish does!  With this mechanism you can easily add another level of visibility by telling OSGi exactly which public you want to be exposed outside of the module.  You get the best of both worlds: Better encapsulation of your code so that maintenance is easier and productivity is increased. Usage of public visibility inside the module so that you can encapsulate intra-module better with packages. How I do this in GlassFish: Carefully plan out at least one package that will contain "true" publics.  This is the package that will be exported by OSGi.  I recommend just one package. Here is how to tell OSGi to use it in GlassFish -- edit osgi.bundle like so:-exportcontents:     org.glassfish.mymodule.truepublics;  version=${project.osgi.version} Now all publics declared in any other packages will be visible module-wide but not outside the module. There is one caveat: Accessing "module-private" items outside of the module is controlled at run-time, not compile-time.  The compiler has no clue that a public in a dependent module isn't really public.  it will happily compile it.  At runtime you will definitely see fireworks.  The good news is that you don't have to wait for the code path that tries to use the "module-private" items to fire.  OSGi will complain loudly when that module gets loaded.  OSGi will refuse to load it.  You will see an error like this: remote failure: Error while loading FOO: Exception while adding the new configuration : Error occurred during deployment: Exception while loading the app : org.osgi.framework.BundleException: Unresolved constraint in bundle com.oracle.glassfish.miscreant.code [115]: Unable to resolve 115.0: missing requirement [115.0] osgi.wiring.package; (osgi.wiring.package=org.glassfish.mymodule.unexported). Please see server.log for more details. That is if you accidentally change code in module B to use a public that is really a "module-private" in module A, then you will see the error immediately when you try to test whatever you were changing in module B.

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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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  • In PHP, what are the different design patterns to implement OO controllers as opposed to procedural controllers?

    - by Ryan
    For example, it's very straightforward to have an index.php controller be a procedural script like so: <?php //include classes and functions //get some data from the database //and/or process a form submission //render HTML using your template system ?> Then I can just navigate to http://mysite.com/index.php and the above procedural script is essentially acting as a simple controller. Here the controller mechanism is a basic procedural script. How then do you make controllers classes instead of procedural scripts? Must the controller class always be tied to the routing mechanism?

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  • Should I use the factory design pattern for every class?

    - by Frog
    I've been writing a website in PHP. As the code becomes more complex, I keep finding problems that can be solved using the factory design pattern. For example: I've a got a class Page which has subclasses HTMLPage, XMLPage, etc. Depending on some input I need to return an object of either one of these classes. I use the factory design pattern to do this. But as I encounter this problem in more classes, I keep having to change code which still initiates an object using its constructor. So now I'm wondering: is it a good idea to change all code so that it uses the factory design pattern? Or are there big drawbacks? I'm currently in a position to change this, so your answers would be really helpful.

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  • May I give a single class multiple responsibilities if only one will ever be reusable?

    - by lnluis
    To the extent that I understand the Single Responsibility Principle, a SINGLE class must only have one responsibility. We use this so that we can reuse other functionalities in other classes and not affect the whole class. My question is: what if the entity has only one purpose that really interacts with the system, and that purpose won't change? Do you have to separate the implementations of your methods into another class and just instantiate those from your entity class? Or to put it another way... Is it ok to break the SRP if you know those functions will not be reusable in the future? Or is it better to assume that we do not know if the functionalities of these methods will be reusable or not, and so just abstract them to other classes?

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  • Separate Action from Assertion in Unit Tests

    - by DigitalMoss
    Setup Many years ago I took to a style of unit testing that I have come to like a lot. In short, it uses a base class to separate out the Arrangement, Action and Assertion of the test into separate method calls. You do this by defining method calls in [Setup]/[TestInitialize] that will be called before each test run. [Setup] public void Setup() { before_each(); //arrangement because(); //action } This base class usually includes the [TearDown] call as well for when you are using this setup for Integration tests. [TearDown] public void Cleanup() { after_each(); } This often breaks out into a structure where the test classes inherit from a series of Given classes that put together the setup (i.e. GivenFoo : GivenBar : WhenDoingBazz) with the Assertions being one line tests with a descriptive name of what they are covering [Test] public void ThenBuzzSouldBeTrue() { Assert.IsTrue(result.Buzz); } The Problem There are very few tests that wrap around a single action so you end up with lots of classes so recently I have taken to defining the action in a series of methods within the test class itself: [Test] public void ThenBuzzSouldBeTrue() { because_an_action_was_taken(); Assert.IsTrue(result.Buzz); } private void because_an_action_was_taken() { //perform action here } This results in several "action" methods within the test class but allows grouping of similar tests (i.e. class == WhenTestingDifferentWaysToSetBuzz) The Question Does someone else have a better way of separating out the three 'A's of testing? Readability of tests is important to me so I would prefer that, when a test fails, that the very naming structure of the tests communicate what has failed. If someone can read the Inheritance structure of the tests and have a good idea why the test might be failing then I feel it adds a lot of value to the tests (i.e. GivenClient : GivenUser : WhenModifyingUserPermissions : ThenReadAccessShouldBeTrue). I am aware of Acceptance Testing but this is more on a Unit (or series of units) level with boundary layers mocked. EDIT : My question is asking if there is an event or other method for executing a block of code before individual tests (something that could be applied to specific sets of tests without it being applied to all tests within a class like [Setup] currently does. Barring the existence of this event, which I am fairly certain doesn't exist, is there another method for accomplishing the same thing? Using [Setup] for every case presents a problem either way you go. Something like [Action("Category")] (a setup method that applied to specific tests within the class) would be nice but I can't find any way of doing this.

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