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  • What patterns exist for web application development?

    - by DaveDev
    I understand that MVC & MVP are design patterns that are commonly used for web development, as well as ASP.NET WebForms (more of an anti-pattern, really!). What other patterns are used in web application development? I'm not necessarily saying I want to learn/use new patterns just to be different - I do believe there's a lot of value in taking the conventional route - but I think it's good to know what else is out there to be able to properly understand what I'm currently working with. Thanks.

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  • How can I define an empty array in a Perl construtor?

    - by Laimoncijus
    I am just beginner with Perl, so if it sounds stupid - sorry for that :) My problem is - I am trying to write a class, which has an empty array, defined in constructor of a class. So I am doing this like this: package MyClass; use strict; sub new { my ($C) = @_; my $self = { items => () }; bless $self, ref $C || $C; } sub get { return $_[0]->{items}; } 1; Later I am testing my class with simple script: use strict; use Data::Dumper; use MyClass; my $o = MyClass->new(); my @items = $o->get(); print "length = ", scalar(@items), "\n", Dumper(@items); And while running the script I get following: $ perl my_test.pl length = 1 $VAR1 = undef; Why am I doing wrong what causes that I get my items array filled with undef? Maybe someone could show me example how the class would need to be defined so I would not get any default values in my array?

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  • Is the a pattern for iterating over lists held by a class (dynamicly typed OO languages)

    - by Roman A. Taycher
    If I have a class that holds one or several lists is it better to allow other classes to fetch those lists(with a getter) or to implement a doXList/eachXList type method for that list that take a function and call that function on each element of the list contained by that object. I wrote a program that did a ton of this and I hated passing around all these lists sometimes with method in class a calling method in class B to return lists contained in class C, B contains a C or multiple C's (note question is about dynamically typed OO languages languages like ruby or smalltalk) ex. (that came up in my program) on a Person class containing scheduling preferences and a scheduler class needing to access them.

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  • domain modeling naming problem

    - by cherouvim
    Hello There are some simple entities in an application (e.g containing only id and title) which rarely change and are being referenced by the more complex entities of the application. These are usually entities such as Country, City, Language etc. How are these called? I've used the following names for those in the past but I'm not sure which is the best way to call them: reference data lookup values dictionaries thanks

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  • C#: why have all static methods/variables in a non-static class?

    - by Craig Johnston
    I have come across a class which is non-static, but all the methods and variables are static. Eg: public class Class1 { private static string String1 = "one"; private static string String2 = "two"; public static void PrintStrings(string str1, string str2) { ... All the variables are static across all instances, so there is no point having separate instances of the class. Is there any reason to create a class such as this?

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  • Observer pattern and violation of Single Responsibility Principle

    - by Devil Jin
    I have an applet which repaints itself once the text has changed Design 1: //MyApplet.java public class MyApplet extends Applet implements Listener{ private DynamicText text = null; public void init(){ text = new DynamicText("Welcome"); } public void paint(Graphics g){ g.drawString(text.getText(), 50, 30); } //implement Listener update() method public void update(){ repaint(); } } //DynamicText.java public class DynamicText implements Publisher{ // implements Publisher interface methods //notify listeners whenever text changes } Isn't this a violation of Single Responsibility Principle where my Applet not only acts as Applet but also has to do Listener job. Same way DynamicText class not only generates the dynamic text but updates the registered listeners. Design 2: //MyApplet.java public class MyApplet extends Applet{ private AppletListener appLstnr = null; public void init(){ appLstnr = new AppletListener(this); // applet stuff } } // AppletListener.java public class AppletListener implements Listener{ private Applet applet = null; public AppletListener(Applet applet){ this.applet = applet; } public void update(){ this.applet.repaint(); } } // DynamicText public class DynamicText{ private TextPublisher textPblshr = null; public DynamicText(TextPublisher txtPblshr){ this.textPblshr = txtPblshr; } // call textPblshr.notifyListeners whenever text changes } public class TextPublisher implments Publisher{ // implements publisher interface methods } Q1. Is design 1 a SPR violation? Q2. Is composition a better choice here to remove SPR violation as in design 2.

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • Is it poor design to create objects that only execute code during the constructor?

    - by Curtix
    In my design I am using objects that evaluate a data record. The constructor is called with the data record and type of evaluation as parameters and then the constructor calls all of the object's code necessary to evaluate the record. This includes using the type of evaluation to find additional parameter-like data in a text file. There are in the neighborhood of 250 unique evaluation types that use the same or similar code and unique parameters coming from the text file. Some of these evaluations use different code so I benefit a lot from this model because I can use inheritance and polymorphism. Once the object is created there isn't any need to execute additional code on the object (at least for now) and it is used more like a struct; its kept on a list and 3 properties are used later. I think this design is the easiest to understand, code, and read. A logical alternative I guess would be using functions that return score structs, but you can't inherit from methods so it would make it kind of sloppy imo. I am using vb.net and these classes will be used in an asp.net web app as well as in a distributed app. thanks for your input

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  • Partial class or "chained inheritance"

    - by Charlie boy
    Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • Improve this generic abstract class

    - by Keivan
    I have the following abstract class design, I was wondering if anyone can suggest any improvements in terms of stronger enforcement of our requirements or simplifying implementing of the ControllerBase. //Dependency Provider base public abstract class ControllerBase<TContract, TType> where TType : TContract, class { public static TContract Instance { get { return ComponentFactory.GetComponent<TContract, TType>(); } } public TContract GetComponent<TContract, TType>() where TType : TContract, class { component = (TType)Activator.CreateInstance(typeof(TType), true); RegisterComponentInstance<TContract>(component); } } //Contract public interface IController { void DoThing(); } //Actual Class Logic public class Controller: ControllerBase<IController,Controller> { public void DoThing(); //internal constructor internal Controller(){} } //Usage public static void Main() { Controller.Instance.DoThing(); } The following facts should always be true, TType should always implement TContract (Enforced using a generic constraint) TContract must be an interface (Can't find a way to enforce it) TType shouldn't have public constructor, just an internal one, is there any way to Enforce that using ControllerBase? TType must be an concrete class (Didn't include New() as a generic constrain since the constructors should be marked as Internal)

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  • C++ Matrix class hierachy

    - by bpw1621
    Should a matrix software library have a root class (e.g., MatrixBase) from which more specialized (or more constrained) matrix classes (e.g., SparseMatrix, UpperTriangluarMatrix, etc.) derive? If so, should the derived classes be derived publicly/protectively/privately? If not, should they be composed with a implementation class encapsulating common functionality and be otherwise unrelated? Something else? I was having a conversation about this with a software developer colleague (I am not per se) who mentioned that it is a common programming design mistake to derive a more restricted class from a more general one (e.g., he used the example of how it was not a good idea to derive a Circle class from an Ellipse class as similar to the matrix design issue) even when it is true that a SparseMatrix "IS A" MatrixBase. The interface presented by both the base and derived classes should be the same for basic operations; for specialized operations, a derived class would have additional functionality that might not be possible to implement for an arbitrary MatrixBase object. For example, we can compute the cholesky decomposition only for a PositiveDefiniteMatrix class object; however, multiplication by a scalar should work the same way for both the base and derived classes. Also, even if the underlying data storage implementation differs the operator()(int,int) should work as expected for any type of matrix class. I have started looking at a few open-source matrix libraries and it appears like this is kind of a mixed bag (or maybe I'm looking at a mixed bag of libraries). I am planning on helping out with a refactoring of a math library where this has been a point of contention and I'd like to have opinions (that is unless there really is an objective right answer to this question) as to what design philosophy would be best and what are the pros and cons to any reasonable approach.

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  • Do you think functional language is good for applications that have a lot of business rules but very

    - by StackUnderflow
    I am convinced that functional programming is an excellent choice when it comes to applications that require a lot of computation (data mining, AI, nlp etc). But is it wise to use functional programming for a typical enterprise application where there are a lot of business rules but not much in terms of computation? Please disregard the fact that there are very few people using functional programming and that it's kind of tough. Thanks

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  • Get XML-RPC (Andorid - PHP) web service different params type

    - by Jovan
    Hi, I want to create XML-RPC web service for Andorid (client) - PHP (Server) communication I create XML-RPC PHP web service server using this tutorial: http://articles.sitepoint.com/article/own-web-service-php-xml-rpc/5 For andorid client web service I use this project: http://code.google.com/p/android-xmlrpc/ server and client communication is OK, but I have problem with getting params from andorid client to php server. From andorid client I send two params (first integer and second float number) Object[] params = { 3, 3.6f, }; method.call(params); , but I don't know how to handle this parameters in php server?? in php server there is some function , but with only one param ($news_id): function news_viewNewsItem ( $news_id ) { /* Define the query to fetch the news item */ $query = "SELECT * FROM kd_xmlrpc_news WHERE news_id = '" . $news_id . "'"; $sql = mysql_query ( $query ); if ( $result = mysql_fetch_array ( $sql ) ) { /* Extract the variables for sending in our server response */ $news_item['news_id'] = $result['news_id']; $news_item['date'] = XMLRPC_convert_timestamp_to_iso8601( mysql_datetime_to_timestamp( $result['date'] ) ); $news_item['title'] = $result['title']; $news_item['full_desc'] = $result['full_desc']; $news_item['author'] = $result['author']; /* Respond to the client with the news item */ XMLRPC_response(XMLRPC_prepare($news_item), KD_XMLRPC_USERAGENT); } else { /* If there was an error, respond with a fault code instead */ XMLRPC_error("1", "news_viewNewsItem() error: Unable to read news:" . mysql_error(), KD_XMLRPC_USERAGENT); } } In server.py file there is functions for every method but I dont know how to write in php server: def add(self, x, y): print print "input x=%s, y=%s" % (str(x), str(y)) sum = x + y print "output", sum print return sum Can some one help me with code , and tell me how to handle various types from client to server?? Thanks and Happy New Year

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • How to signal object instantiation in a Collaboration/Communication Diagram?

    - by devoured elysium
    I'd like to know how to translate the following line of code to a Collaboration Diagram: Food food = new Food("abc", 123); I know that I can call an Food's method using the following notation: MyStaticMethod() ----------------------> -------- | | | Food | | | -------- being that equivalent to Taste taste = Food.MyStaticMethod(); and MyInstanceMethod() ----------------------> --------------- | | | food : Food | | | --------------- is equivalent to food.MyInstanceMethod(); but how do I signal that I want to call a given constructor on Food? Thanks

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  • Compromising design & code quality to integrate with existing modules

    - by filip-fku
    Greetings! I inherited a C#.NET application I have been extending and improving for a while now. Overall it was obviously a rush-job (or whoever wrote it was seemingly less competent than myself). The app pulls some data from an embedded device & displays and manipulates it. At the core is a communications thread in the main application form which executes a 600+ lines of code method which calls functions all over the place, implementing a state machine - lots of if-state-then-do type code. Interaction with the device is done by setting the state/mode globally and letting the thread do it's thing. (This is just one example of the badness of the code - overall it is not very OO-like, it reminds of the style of embedded C code the device firmware is written in). My problem is that this piece of code is central to the application. The software, communications protocol or device firmware are not documented at all. Obviously to carry on with my work I have to interact with this code. What I would like some guidance on, is whether it is worth scrapping this code & trying to piece together something more reasonable from the information I can reverse engineer? I can't decide! The reason I don't want to refactor is because the code already works, and changing it will surely be a long, laborious and unpleasant task. On the flip side, not refactoring means I have to sometimes compromise the design of other modules so that I may call my code from this state machine! I've heard of "If it ain't broke don't fix it!", so I am wondering if it should apply when "it" is influencing the design of future code! Any advice would be appreciated! Thanks!

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  • Java generics question

    - by user247866
    So I have 3 classes. Abstract class A Class B extends class A independent Class C In class D that contains the main method, I create a list of instances of class B List<B> b = methodCall(); // the method returns a list of instances of class B Now in class C I have one method that is common to both A and B, and hence I don't want to duplicate it. I want to have one method that takes as input an instance of class A, as follows: public void someMethod(List<A> a) However, when I do: C c = new C(); c.someMethod(b); I get an error that some-method is not applicable for the argument List<B>, instead it's expecting to get List<A>. Is there a good way to fix this problem? Many thanks!

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  • PHP static objects giving a fatal error

    - by Webbo
    I have the following PHP code; <?php component_customer_init(); component_customer_go(); function component_customer_init() { $customer = Customer::getInstance(); $customer->set(1); } function component_customer_go() { $customer = Customer::getInstance(); $customer->get(); } class Customer { public $id; static $class = false; static function getInstance() { if(self::$class == false) { self::$class = new Customer; } else { return self::$class; } } public function set($id) { $this->id = $id; } public function get() { print $this->id; } } ?> I get the following error; Fatal error: Call to a member function set() on a non-object in ....../classes/customer.php on line 9 Can anyone tell me why I get this error? I know this code might look strange, but it's based on a component system that I'm writing for a CMS. The aim is to be able to replace HTML tags in the template e.g.; <!-- component:customer-login --> with; <?php component_customer_login(); ?> I also need to call pre-render methods of the "Customer" class to validate forms before output is made etc. If anyone can think of a better way, please let me know but in the first instance, I'd like to know why I get the "Fatal error" mentioned above. Cheers

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  • What's The Best Object-Relational Mapping Tool For .NET?

    - by Icono123
    I've worked on a few Java web projects and we've always used Hibernate for our data object layer. I haven't worked on a large scale ASP.NET site and I'm unsure which solution to choose. I'm tempted to try NHibernate, but I don't like the fact that they use so many third party libraries. I found this list on Wikipedia of available ORM software: http://en.wikipedia.org/wiki/List_of_object-relational_mapping_software#.NET What ORM have you used? Was it easy to use? Would you recommend using it again? Was it used on a small, medium, or large project? Would you write your own? Thanks.

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  • Define an empty array in Perl class new()

    - by Laimoncijus
    Hi, I am just beginner with Perl, so if it sounds stupid - sorry for that :) My problem is - I am trying to write a class, which has an empty array, defined in constructor of a class. So I am doing this like this: package MyClass; use strict; sub new { my ($C) = @_; my $self = { items => () }; bless $self, ref $C || $C; } sub get { return $_[0]->{items}; } 1; Later I am testing my class with simple script: use strict; use Data::Dumper; use MyClass; my $o = MyClass->new(); my @items = $o->get(); print "length = ", scalar(@items), "\n", Dumper(@items); And while running the script I get following: $ perl my_test.pl length = 1 $VAR1 = undef; Why am I doing wrong what causes that I get my items array filled with undef? Maybe someone could show me example how the class would need to be defined so I would not get any default values in my array? Thanks!

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