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• Rails - inheritance hierarchy of classes where a subtype can play two roles

  - by Miquel

  I need to model Owners and Rentees in an application, so you have stuff that is always owned by someone and can be rented for someone else. I first approached this problem with Single Table Inheritance because both types of person will share all attributes, so you would have a model called Person associated to a table people with Owner and Rentee inheriting from Person. The problem is that Single type inheritance discerns subtypes using a field type and therefore a record in the table can represent either an Owner or a Rentee but not both at the same time, while in the real context you can have an Owner which is renting something from another Owner and therefore that person is at the same time an Owner and a Rentee. How would you approach this problem? Would you use separated tables for owners and rentees? Is there any other type of table inheritance in Rails?

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• Does [Serializable] work for inherited classes?

  - by MattiasK

  I haven't worked much with remoting so excuse this rather rudimentary question, If I derive a class from an abstract class marked as [Serializable] (for passing the data across an appdomain), does the other side get the actual overriden implementation? ie does polymorphism work over remoting/Serializable? I need to create a clone on the other side rather than operating on the original so MarshalByRef is not an option...

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• Using enums in Java across multiple classes

  - by Richard Mar.

  I have the following class: public class Card { public enum Suit { SPACES, HEARTS, DIAMONDS, CLUBS }; public Card(Suit nsuit, int nrank) { suit = nsuit; rank = nrank; } private Suit suit; private int rank; } I want to instantiate it in another class, but that class doesn't understand the Suit enum. Where should I put the enum to make it publicly visible?

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• STLifying C++ classes

  - by shambulator

  I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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• Dynamic proxies to auto-save models

  - by atomman

  I'm trying to make some auto-magic happen in java using proxies to track objects and saving them when a set* method is called. I started of using java's built in Proxy, and everything works just fine, but from what I can understand I need a interface for every model, which is something that I'm trying to avoid. This is where CGLIB comes in, it allows me to create proxies of my models without the use of interfaces. BUT, how can I now retrieve the original object, the one I am trying to save? The optimal solution to be would be something like the EntityManager interface used by hibernate, where you keep your original object, but it is still tracked.

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• Toggle classes with radio button in jQuery

  - by dardub

  I have a set of radio buttons where when I click a radio button, I want the label to change color or whatever. But when I click another radio button, the color goes away. Therefore I have something like this: jQuery('label').mouseup(function(){ jQuery(this).prev().attr('checked', 'checked'); jQuery('input').next().removeClass('selected'); jQuery('input:checked').next().addClass('selected'); }); if you need to see some html: <input type="radio" id="radio1" name="myRadio" value="option-1" /> <label for="radio1">Swing Gate</label> <input type="radio" id="radio2" name="myRadio" value="option-2" /> <label for="radio2">Swing Gate</label> This first removes 'selected' class from all the labels and then re-applies to only the checked labels. It works and is simple, but I was thinking this might not be the most efficient way of doing this. I imagine that javascript is iterating through each input element and using more resources than necessary. I'm curious if anyone knows of a common way of doing this more efficiently. I seem to be doing this type of thing quite often in my jQuery code. I've just been using jQuery for the past 3 months or so btw.

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• Programming languages and constructors

  - by jreicher

  Why is a constructor not considered as member of a class ? Is there any specific reason ? Thanks. EDIT: Language is C#

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• jquery switch element classes

  - by Sobakinet

  Please take a look here: http://jsfiddle.net/ZUd27/7/ What I need: There are several elements. One of them is active and visible. If I hover over any inactive element, it becomes visible and active. The previously active element becomes inactive. On mouseout, nothing happens - the last hovered element stays active. My problems: The first active element always stays active (in DOM?). It becomes invisible, but on next mouseover nothing happens. Other elements don't behave as they should. If one of them is active, on next mousein it becomes invisible. thx

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• Centering CSS Page - Classes conflicted

  - by Tran

  Hello everyone, I cant center this page, no matter what. It's a simple task. Sorry Im so new to CSS. Please help.... http://imageoneads.com/zenliver/

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• How to declare different non-JPA annotations on embedded classes

  - by e99y

  @Embedded public class EmbedMe { private String prop1; private String prop2; } @Entity public class EncryptedEmbedded { @Embeddable private EmbedMe enc; } I am current using Jasypt for encryption. Is there a way to indicate that the @Embeddable in EncryptedEmbedded will use @Type(value = "newDeclaredTypeHere") per attribute (prop1, prop2)? Thanks in advance... ;)

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• How classes are secure than structures ?

  - by Asad Hanif

  Structure's member are public by default ans class's members are private by default. We can access private data members through a proper channel (using member function). If we have access to member functions we can read/write data in private data member, so how it is secure...we are accessing it and we are changing data too.....

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• Will my shared variables loose value? (asp.net vb)

  - by Phil

  I have a class includes.vb that holds some variables (sharing them with other pages) like: Public Shared pageid As Integer = 0 I then have a function that does some work with these variables returning them with values; Return pageid When I step through the code, the variables have values (while stepping through the function), but when they are returned to the page, they come back null. Do they loose value everytime a page is loaded? Can you suggest an alternative method? Thanks a lot.

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• Using Classes / OOP in PHP

  - by Alex Demchak

  I'm pretty proficient with PHP, outside of OOP - which I am just now starting to jump in to. I've been watching videos and reading tutorials, but they are all still pretty confusing... If I have FILE 1 (class.time.php) class Time { function GetTime(){ $time = date('H:i:s'); printf($time); } } and then in a nother php page I've got FILE 2 (page.php) I can do include('class.time.php'); and then anywhere in this page I can then do $time = new Time; //Calling the class and setting the class to a variable $time->GetTime(); //This is BASICALLY saying (run the 'GetTime' function in the 'Time Class' My main question is, is the comment above (This is BASICALLY saying.....) correct? or is there a better way to think of it?

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• Why does coffeescript generate classes like this?

  - by ryeguy

  Given the following coffeescript code: class Animal constructor: (@name) -> speak: (things) -> "My name is #{@name} and I like #{things}" This is generated: var Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.speak = function(things) { return "My name is " + this.name + " and I like " + things; }; return Animal; })(); But why isn't this more idiomatic code generated? var Animal = function Animal(name) { this.name = name; }; Animal.prototype.speak = function(things) { return "My name is " + this.name + " and I like " + things; }; I know that coffeescript wraps a lot of stuff in anonymous functions to control scope leak, but what could leak here?

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• writing structs and classes to disk

  - by Phenom

  The following function writes a struct to a file. int btwrite(short rrn, BTPAGE *page_ptr) { long addr; addr = (long) rrn * (long) PAGESIZE + HEADERSIZE; lseek(btfd, addr, 0); return (write(btfd, page_ptr, PAGESIZE)); } The following is the struct. typedef struct { short keycount; /* number of keys in page */ int key[MAXKEYS]; /* the actual keys */ int value[MAXKEYS]; /* the actual values */ short child[MAXKEYS+1]; /* ptrs to rrns of descendants */ } BTPAGE; What would happen if I changed the struct to a class, would it still work the same? If I added class functions, would the size it takes up on disk increase?

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• c++ classes & lua

  - by anon

  I want to have C++ objects that I can read/write in both C++ & Lua. I have looked at: http://www.lua.org/pil/28.html However, I do not like that solution, since my objects have constructors & destructors (and they are important as I use RAII and these take care of reference counts). What I don't like in the PIL solution is that the object is allocated in Lua's heap. What i want instead, is to create hte C++ object on my own, and just have lua have a way to do get/set on them. Does anyone have a good tutorial/link on this? Tanks!

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• "No Suggestions" in NetBeans

  - by Flexx

  For a few days now I'm using NetBeans 6.8 for doing PHP work. But even if a class-file is included and the methods are public and there's phpDoc used, NetBeans everytime shows "No Suggestions" in the window. E.g. I type $user-> and press CTRL+Space, I do expect all the methods and variables but there aren't shown any. ideas?

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• How to find the byte offset of an object in C++?

  - by Phenom

  Let's say I create 5 objects. Would the byte offset of the first object be 0? How would I find out the byte offset of the other objects?

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• When to use () with classes?

  - by SoulBeaver

  This is really starting to confuse the hell out of me. When do I use them, when don't I? For example I was reading a .cpp on linked lists whose class declaration was: struct CarPart { long PartNumber; char Partname[40]; double UnitPrice; CarPart *next; }; class ListOfParts { int size; public: CarPart *head; ListOfParts(); ~ListOfParts(); const int count() const; void insert( CarPart *item ); CarPart *retrieve( int pos ); }; With this code, why am I allowed to write ListOfParts *pPart = new ListOfParts(); CarPart *pCarPart = new CarPart; Declaring an instance of ListOfParts requires (), but not my CarPart? That's confusing me. When I asked a question before and people told me that such a declaration is a function that returns a ListOfParts object, but not the actual constructor. So I'm guessing this is still something different. What's happening here? PS: Am I correct to assume that the const to the right of count() means I cannot modify any values in count?

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• Ruby forwarding method calls

  - by JP

  I have an instance of a master class which generates instances of a subclass, these subclasses need to forward some method calls back to the master instance. At the moment I have code looking something like this, but it feels like I should be able to do the same thing more efficiently (maybe with method_missing?) class Master def initalize(mynum) @mynum = mynum end def one_thing(subinstance) "One thing with #{subinstance.var} from #{@mynum}" end def four_things(subinstance) "Four things with #{subinstance.var} from #{@mynum}" end def many_things(times,subinstance) "#{times} things with #{subinstance.var} from #{@mynum}" end def make_a_sub(uniqueness) Subthing.new(uniqueness,self) end class Subthing def initialize(uniqueness,master) @u = uniqueness @master = master end # Here I'm forwarding method calls def one_thing master.one_thing(self) end def four_things master.four_things(self) end def many_things(times) master.many_things(times,self) end end end m = Master.new(42) s = m.make_a_sub("very") s.one_thing === m.one_thing(s) s.many_things(8) === m.many_things(8,s) I hope you can see what's going on here. I would use method_missing, but I'm not sure how to cope with the possibility of some calls having arguments and some not (I can't really rearrange the order of the arguments to the Master methods either) Thanks for reading!

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• storage classes

  - by ramyabanu

  what is the difference between a variable declared as an auto and static? what is the difference in allocation of memory in auto and static variable? why do we use static with array of pointers and what is its significance?

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• how to organize classes in ruby if they are literal subclasses

  - by RetroNoodle

  I know that title didn't make sense, Im sorry! Its hard to word what I am trying to ask. I had trouble googling it for the same reason. So this isn't even Ruby specific, but I am working in ruby and I am new to it, so bear with me. So you have a class that is a document. Inside each document, you have sentences, and each sentence has words. Words will have properties, like "noun" or a count of how many times they are used in the document, etc. I would like each of the elements, document, sentence, word be an object. Now, if you think literally - sentences are in documents, and words are in sentences. Should this be organized literally like this as well? Like inside the document class you will define and instantiate the sentence objects, and inside the sentence class you will define and instantiate the words? Or, should everything be separate and reference each other? Like the word class would sit outside the sentence class but the sentence class would be able to instantiate and work with words? This is a basic OOP question I guess, and I suppose you could argue to do it either way. What do you guys think? Each sentence in the document could be stored in a hash of sentence objects inside the document object, and each word in the sentence could be stored in a hash of word objects inside the sentence. I dont want to code myself into a corner here, thats why I am asking, plus I have wondered this before in other situations. Thank you!

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• Constructors in Inner classes (implementing Interfaces)

  - by thepandaatemyface

  Hi, How would I go about writing a constructor for an inner class which is implementing an interface? I know I could make a whole new class, but I figure there's got to be a way to do something along the line of this: JButton b = new JButton(new AbstractAction() { public AbstractAction() { super("This is a button"); } public void actionPerformed(ActionEvent e) { System.out.println("button clicked"); } }); When I enter this it doesn't recognize the AbstractAction method as a constructor (compiler asks for return type). Anyone have an idea? Thanks

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• fluent nhibernate - storing and retrieving three classes in/from one table

  - by Will I Am

  Noob question. I have this situation where I have these objects: class Address { string Street; string City; ... } class User { string UserID; Address BillingAddress; Address MailingAddress; ... } What is the proper way of storing this data using (fluent) nHibernate? I could use a separate Address table and create a reference, but they are 1:1 relationships so I don't really want to incur the overhead of a join. Ideally I would store this as a single flat record. So, my question is, what is the proper way of storing an instance of class 'User' in such a way that it stores its contents and also the two addresses as a single record? My knowledge is failing me on how I can store this information in such a way that the two Address records get different column names (e.g. BillingAddress_Street and MailingAddress_Street, for example), and also how to read a record back into a User instance.

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• Passing a NSString to another ViewController using classes

  - by Jeff Kranenburg

  I know this insanely simple, but I am re-teaching myself the basics and trying to get my head around this:-) I have one ViewController called MainVC and I have one called ClassVC In ClassVC I have this code: @interface ClassVC : UIViewController { NSString *mainLine; } @property (nonatomic, retain) NSString *mainLine; @end and I have this in the implementation file: @synthesize mainLine = _mainLine; -(NSString *)_mainLine { _mainLine = @"This a string from a Class"; return _mainLine; } Now I was thinking that if I #import the ClassVC into MainVC I would be able to transfer that string along as well like so: This code is in the viewDidLoad _mainLabel.text = _secondClass.mainLine; NSLog(@"%@", _secondClass.mainLine); But that is not working - so cannot I not pass strings in through this way???

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