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  • PHP Nested classes work... sort of?

    - by SeanJA
    So, if you try to do a nested class like this: //nestedtest.php class nestedTest{ function test(){ class E extends Exception{} throw new E; } } You will get an error Fatal error: Class declarations may not be nested in [...] but if you have a class in a separate file like so: //nestedtest2.php class nestedTest2{ function test(){ include('e.php'); throw new E; } } //e.php class E Extends Exception{} So, why does the second hacky way of doing it work, but the non-hacky way of doing it does not work?

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  • How to create extensible dynamic array in Java without using pre-made classes?

    - by AndrejaKo
    Yeah, it's a homework question, so givemetehkodezplsthx! :) Anyway, here's what I need to do: I need to have a class which will have among its attributes array of objects of another class. The proper way to do this in my opinion would be to use something like LinkedList, Vector or similar. Unfortunately, last time I did that, I got fire and brimstone from my professor, because according to his belief I was using advanced stuff without understanding basics. Now next obvious solution would be to create array with fixed number of elements and add checks to get and set which will see if the array is full. If it is full, they'd create new bigger array, copy older array's data to the new array and return the new array to the caller. If it's mostly empty, they'd create new smaller array and move data from old array to new. To me this looks a bit stupid. For my homework, there probably won't be more that 3 elements in an array, but I'd like to make a scalable solution without manually calculating statistics about how often is array filled, what is the average number of new elements added, then using results of calculation to calculate number of elements in new array and so on. By the way, there is no need to remove elements from the middle of the array. Any tips?

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  • Is it good practice to generally make heavyweight classes non-copyable?

    - by Emile Cormier
    I have a Shape class containing potentially many vertices, and I was contemplating making copy-constructor/copy-assignment private to prevent accidental needless copying of my heavyweight class (for example, passing by value instead of by reference). To make a copy of Shape, one would have to deliberately call a "clone" or "duplicate" method. Is this good practice? I wonder why STL containers don't use this approach, as I rarely want to pass them by value.

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  • Can LINQ expression classes implement the observer pattern instead of deferred execution?

    - by Tormod
    Hi. We have issues within an application using a state machine. The application is implemented as a windows service and is iteration based (it "foreaches" itself through everything) and there are myriads of instances being processed by the state machine. As I'm reading the MEAP version of Jon Skeets book "C# in Depth, 2nd ed", I'm wondering if I can change the whole thing to use linq expression instances so that guards and conditions are represented using expression trees. We are building many applications on this state machine engine and would probably greatly benefit from the new Expression tree visualizer in VS 2010 Now, simple example. If I have an expression tree where there is an OR Expression condition with two sub nodes, is there any way that these can implement the observer pattern so that the expression tree becomes event driven? If a condition change, it should notify its parent node (the OR node). Since the OR node then changes from "false" to "true", then it should notify ITS parent and so on. I love the declarative model of expression trees, but the deferred execution model works in opposite direction of the control flow if you want event based "live" conditions. Am I off on a wild goose chase here? Or is there some concept in the BCL that may help me achieve this?

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  • What's the best way to validate EntityFramwork 4.0 classes?

    - by lsb
    Hi! I've done a fair amount of searching but I've yet to find an easy way to validate EntityFramework 4.0 entities passed accross the wire via WCF Data Services. Basically, I want to do something on the client like: Proxy.MyEntities entities = new Proxy.MyEntities( new Uri("http://localhost:2679/Service.svc")); Proxy.Vendor vendor = new Proxy.Vendor(); vendor.Code = "ABC/XYZ"; vendor.Status = "ACTIVE"; // I'd like to do something like the following: vendor.Validate(); entities.AddToVendors(vendor); entities.SaveChanges(); Any help in this regard would be greatly appreciated!

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  • Why can't you call abstract functions from abstract classes in PHP?

    - by incrediman
    I've set up an abstract parent class, and a concrete class which extends it. Why can the parent class not call the abstract function? //foo.php <?php abstract class AbstractFoo{ abstract public static function foo(); public static function getFoo(){ return self::foo();//line 5 } } class ConcreteFoo extends AbstractFoo{ public static function foo(){ return "bar"; } } echo ConcreteFoo::getFoo(); ?> Error: Fatal error: Cannot call abstract method AbstractFoo::foo() in foo.php on line 5

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  • In Ruby, how can I initialize instance variables in new objects of core classes created from literal

    - by Ollie Saunders
    class Object attr_reader :foo def initialize @foo = 'bar' end end Object.new.foo # => 'bar' ''.foo # => nil //.foo # => nil [].foo # => nil I want them all to return 'bar' Am aware that you can do this already: class Object def foo 'bar' end end But I specifically want to initialize a state variable. Also note that this doesn't work. class String alias_method :old_init, :initialize def initialize(*args) super old_init(*args) end end class Object attr_reader :foo def initialize @foo = 'bar' super end end ''.foo # => nil Nor does this: class String attr_reader :foo def initialize @foo = 'bar' end end ''.instance_variables # => [] I'm beginning to think that this isn't actually possible.

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  • How do I solve an unresolved external when using C++ Builder packages (with TForm based classes)?

    - by José Renato
    Hi, i'm working with Bulder C++ 6 and 2010, and i'm having this problem: http://stackoverflow.com/questions/2727001/how-do-i-solve-an-unresolved-external-when-using-c-builder-packages But, the difference here is that i'm using a FORM compiled inside the package, so, take the example above, but in addition i'm including a form classe, like TForm2: class TForm2 : public TForm { __published: // IDE-managed Components TButton *Button1; void __fastcall Button1Click(TObject *Sender); private: // User declarations public: // User declarations __fastcall TForm2(TComponent* Owner); }; //--------------------------------------------------------------------------- extern PACKAGE TForm2 *Form2; //--------------------------------------------------------------------------- So, when i'm trying to use this class in any project the linker stops and give me the unresolved external error. When i got that error i tried to include the word PACKAGE, like this: class PACKAGE TForm2 But, when i tried to compile the PACKAGE, the compiler stops with the unresolved external error: [ILINK32 Error] Error: Unresolved external '__fastcall Forms::TCustomForm::~TCustomForm()' referenced from c:\projects\UNIT2.OBJ How can i solve this problem? PS.: Sorry about the bad English.

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  • Why isn't DBIx::Class::Schema::Loader creating my classes?

    - by Robert Wohlfarth
    I am trying to generate static schemas using DBIx::Class in Perl. The command shown below outputs a Schema.pm and no other files. Any idea what I'm doing wrong, or how to to debug this? U:\wohlfarj\Software\PARS>perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:.\lib -e "make_schema_at('PARS::Schema',{debug=>1},['dbi:ODBC:PARS','user','password',{AutoCommit=>0}])" Dumping manual schema for PARS::Schema to directory .\lib ... Schema dump completed. I'm using Strawberry Perl on Windows XP. The database is SQL Server 2000, accessed through an ODBC connection. I can successfully run queries using plain old DBI with the same ODBC connection.

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  • Strategy game programming in Java, how the map and unit classes should work/relate each other.

    - by Gabriel A. Zorrilla
    As a way of learning Java i'm doing a little strategy game. You have a game map and military units. The gamemap and the units are Jpanels which are binded together in another class called GameWindow, which has a JLayeredPane where the gamepap is below the units. Every time i click a unit (and therefore, the JPane) I can get the unit's information. The problem comes when i want to move a unit... each unit is self drawn inside it's Jpanel, how do i represent the change in position over the gamemap? I'm thinking about reloading the whole game window based on a position change of a unit (because the JPAnels that represent the units are created in the GameWindow, not drawn in the gamemap). Another more elegant option, should be repainting the whole map, with the units. But that way the units would lose it's status of objects (no more JPAnels, just being drawn in the gamemap paint() method), and how would i tell if one unit is clicked? I dont know how people with more experience in games handle the class structure in strategy games. I believe i have the right structure (map, game units, each one an object) but I'm having difficulties making it work together. Here is a snapshot of the map with a couple of units:

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  • How can I dynamically override a classes "each" method?

    - by rewbs
    Groovy adds each() and a number of other methods to java.lang.Object. I can't figure out how to use the Groovy metaclass to dynamically replace the default each() on a Java class. I can see how to add new methods: MyJavaClass.metaClass.myNewMethod = { closure -> /* custom logic */ } new MyJavaClass().myNewMethod { item -> println item } // runs custom logic But it seems the same approach doesn't work when overriding methods: MyJavaClass.metaClass.each = { closure -> /* custom logic */ } new MyJavaClass().each { item -> println item } // runs Object.each() What am I doing wrong? How can I dynamically override each() in Groovy?

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  • How do I integrate GUI elements from different classes at runtime?

    - by thefourthdoctor
    I'm trying to "future-proof" an application that I'm writing by splitting out those elements that are likely to change over time. In my application I need to be able to adapt to changes in the output format (e.g. today I output to a CSV file, in the future I may need to output directly to a SQL Server database, or to a web service, etc.). I'm handling this by defining an abstract class ("OutputProvider") that I will subclass for each individual case. The one aspect of this that has me stumped is how to provide a configuration GUI that is specific to each concrete class. I have a settings dialog with a tab for output configuration. On that tab I intend to provide a drop-down to select the provider and a JPanel beneath it to hold the contents of the provider-specific GUI. How do I get the right GUI in that panel at runtime and have it behave correctly with respect to events? Also, a bonus would be if there was a way to do this such that in order to add support for new providers I could simply provide a new jar or class file to be dropped in a specific folder and the application could pick that up at startup. I'm using NetBeans and Swing.

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  • Rails: creating a custom data type, to use with generator classes and a bunch of questions related t

    - by Shyam
    Hi, After being productive with Rails for some weeks, I learned some tricks and got some experience with the framework. About 10 days ago, I figured out it is possible to build a custom data type for migrations by adding some code in the Table definition. Also, after learning a bit about floating points (and how evil they are) vs integers, the money gem and other possible solutions, I decided I didn't WANT to use the money gem, but instead try to learn more about programming and finding a solution myself. Some suggestions said that I should be using integers, one for the whole numbers and one for the cents. When playing in script/console, I discovered how easy it is to work with calculations and arrays. But, I am talking to much (and the reason I am, is to give some sufficient background). Right now, while playing with the scaffold generator (yes, I use it, because I like they way I can quickly set up a prototype while I am still researching my objectives), I like to use a DRY method. In my opinion, I should build a custom "object", that can hold two variables (Fixnum), one for the whole, one for the cents. In my big dream, I would be able to do the following: script/generate scaffold Cake name:string description:text cost:mycustom Where mycustom should create two integer columns (one for wholes, one for cents). Right now I could do this by doing: script/generate scaffold Cake name:string description:text cost_w:integer cost_c:integer I had also had an idea that would be creating a "cost model", which would hold two columns of integers and create a cost_id column to my scaffold. But wouldn't that be an extra table that would cause some kind of performance penalty? And wouldn't that be defy the purpose of the Cake model in the first place, because the costs are an attribute of individual Cake entries? The reason why I would want to have such a functionality because I am thinking of having multiple "costs" inside my rails application. Thank you for your feedback, comments and answers! I hope my message got through as understandable, my apologies for incorrect grammar or weird sentences as English is not my native language.

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  • Problem with adding and removing classes with jQuery when hovering over a list item.

    - by Andrew
    I want to add a class to a list item when I hover over it, and then remove it and add it to a different list item if a different list item is hovered over. Here's what I tried: jQuery - $(document).ready(function() { $("#results").text("Tournaments"); $("#Tournaments").addClass("box-active"); $("#box ul li").hover(function() { var show = $(this).attr('id'); $("#results").text(show); $("#box ul li").each(function() { $(this).removeClass("box-active"); }); $("#box ul li#" + show).addClass("box-active"); }); }); HTML - <div id="box"> <ul> <li id="Tournaments">Tournaments</li> <li id="Join">Join</li> <li id="Forums">Forums</li> <li id="GameBattles">GameBattles</li> <li id="Practice">Practice</li> </ul> <p>Hovering over: <span id="results"></span></p> </div> When I hover over an item, it changes the class, but if I hover over I different one it removes the class over the item I first hovered over, but doesn't add the class to the new item I'm hovering over. Not sure why, and any help would be appreciated.

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  • Designing different Factory classes (and what to use as argument to the factories!)

    - by devoured elysium
    Let's say we have the following piece of code: public class Event { } public class SportEvent1 : Event { } public class SportEvent2 : Event { } public class MedicalEvent1 : Event { } public class MedicalEvent2 : Event { } public interface IEventFactory { bool AcceptsInputString(string inputString); Event CreateEvent(string inputString); } public class EventFactory { private List<IEventFactory> factories = new List<IEventFactory>(); public void AddFactory(IEventFactory factory) { factories.Add(factory); } //I don't see a point in defining a RemoveFactory() so I won't. public Event CreateEvent(string inputString) { try { //iterate through all factories. If one and only one of them accepts //the string, generate the event. Otherwise, throw an exception. return factories.Single(factory => factory.AcceptsInputString(inputString)).CreateEvent(inputString); } catch (InvalidOperationException e) { throw new InvalidOperationException("No valid factory found to generate this kind of Event!", e); } } } public class SportEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("SportEvent1"); } public Event CreateEvent(string inputString) { return new SportEvent1(); } } public class MedicalEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("MedicalEvent1"); } public Event CreateEvent(string inputString) { return new MedicalEvent1(); } } And here is the code that runs it: static void Main(string[] args) { EventFactory medicalEventFactory = new EventFactory(); medicalEventFactory.AddFactory(new MedicalEvent1Factory()); medicalEventFactory.AddFactory(new MedicalEvent2Factory()); EventFactory sportsEventFactory = new EventFactory(); sportsEventFactory.AddFactory(new SportEvent1Factory()); sportsEventFactory.AddFactory(new SportEvent2Factory()); } I have a couple of questions: Instead of having to add factories here in the main method of my application, should I try to redesign my EventFactory class so it is an abstract factory? It'd be better if I had a way of not having to manually add EventFactories every time I want to use them. So I could just instantiate MedicalFactory and SportsFactory. Should I make a Factory of factories? Maybe that'd be over-engineering? As you have probably noticed, I am using a inputString string as argument to feed the factories. I have an application that lets the user create his own events but also to load/save them from text files. Later, I might want to add other kinds of files, XML, sql connections, whatever. The only way I can think of that would allow me to make this work is having an internal format (I choose a string, as it's easy to understand). How would you make this? I assume this is a recurrent situation, probably most of you know of any other more intelligent approach to this. I am then only looping in the EventFactory for all the factories in its list to check if any of them accepts the input string. If one does, then it asks it to generate the Event. If you find there is something wrong or awkward with the method I'm using to make this happen, I'd be happy to hear about different implementations. Thanks! PS: Although I don't show it in here, all the different kind of events have different properties, so I have to generate them with different arguments (SportEvent1 might have SportName and Duration properties, that have to be put in the inputString as argument).

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  • Is there a design pattern for injecting methods into a class?

    - by glenn I.
    I have a set of classes that work together (I'm coding in javascript). There is one parent class and a number of child classes that are instantiated by the parent class. I have a number of clients of these classes that each need to add on one more methods to the parent or child classes. Rather than having each client inherit from these classes, which is doable but messy because of the child classes, I am having these clients pass functions into the parent class when they instantiate the main class. The main class creates the methods dynamically and the clients can call the methods like they were there all along. My questions are: is this a sensible thing to do? what would the design pattern be for what I am doing?

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  • Why do C# containers and GUI classes use int and not uint for size related members ?

    - by smerlin
    I usually program in C++, but for school i have to do a project in C#. So i went ahead and coded like i was used to in C++, but was surprised when the compiler complained about code like the following: const uint size = 10; ArrayList myarray = new ArrayList(size); //Arg 1: cannot convert from 'uint' to 'int Ok they expect int as argument type, but why ? I would feel much more comfortable with uint as argument type, because uint fits much better in this case. Why do they use int as argument type pretty much everywhere in the .NET library even if though for many cases negative numbers dont make any sense (since no container nor gui element can have a negative size). If the reason that they used int is, that they didnt expect that the average user cares about signedness, why didnt they add overloads for uint additonally ? Is this just MS not caring about sign correctness or are there cases where negative values make some sense/ carry some information (error code ????) for container/gui widget/... sizes ?

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  • What is the best way to declare sorted association in grails domain classes ?

    - by fabien7474
    It seems that there are two different ways of declaring sorted associations in Grails : Method 1 (see here) using default sort order class Book { String title } class Author { static hasMany = [books : Book] static mapping = { books sort: "title"} } Method 2 (see here) using SortedSet class Book implements Comparable { String title int compareTo(obj) { title <=> obj.title } } class Author { SortedSet books static hasMany = [books : Book] } I am not sure which one to use and what is the difference (if any), pros and cons between using one against the other. I would appreciate any clarification. Thank you

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  • How can you logically group HTML elements without taking the help of CSS classes ?

    - by Perpetualcoder
    I know that in jQuery you can use something like $(".cssClass") to get all elements with this class. However in plain html and javascript how do you group elements logically? For example: <input id="fee1" data-id="1" data-group="Fees" type="text" value="$15.00"/> <input id="fee2" data-id="2" data-group="Fees" type="text" value="$25.00"/> <input id="fee3" data-id="3" data-group="Fees" type="text" value="$35.00"/> I want to create a javascript function like this: function GetByDataGroup(dataGroup){ /* returns something like [[1,"$15.00"],[2,"$25.00"],[3,"$35.00"]]*/ } EDIT : Due to some political reasons I cant use jQuery or any framework..i know it doesnt make sense :)

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  • Classes with the same name - is it restricted only within the same translation unit?

    - by LeopardSkinPillBoxHat
    Let's just I had the following code: foo.h class Foo { // ... }; foo.cpp #include "foo.h" // Functions for class Foo defined here... Let's say that Foo are built into a static library foo.lib. Now let's say I have the following: foo2.h class Foo { // ... }; foo2.cpp #include "foo2.h" // Functions for class Foo defined here... This is built into a separate static library foo2.lib. Now, if I re-link foo.lib and foo2.lib into an executable program foo.exe, should it be complaining that class Foo has been defined twice? In my experiences, neither the compiler or the linker are complaining. I wouldn't be expecting the compiler to complain, because they have been defined in separate translation units. But why doesn't the linker complain? How does the linker differentiate between the 2 versions of the Foo class? Does it work by decorating the symbols?

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  • How do you parse text in Ruby on Rails and add classes to specific parts of it?

    - by codyvbrown
    I am a Rails novice and I'm creating an application that I'd love some help on. The app is for social reading. It enables a user to highlight a passage from a text then have that passage saved and bolded into the view for later reading by anyone else. I have no problem creating an if statement on whether a certain string of text is in a passage but how do I add a class to that string and have a group of these passages absorbed back into the view. Any strategic advice would be greatly appreciated.

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  • Where do you extend classes in your rails application?

    - by ro
    Just about to extend the Array class with the following extension: class Array def shuffle! size.downto(1) { |n| push delete_at(rand(n)) } self end end However, I was wondering where a good place to keep these sort of extensions. I was thinking environment.rb or putting in its own file in the initializers directory.

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