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• Rails: Polymorphic User Table a good idea with AuthLogic?

  - by sscirrus

  Hi everyone, I have a system where I need to login three user types: customers, companies, and vendors from one login form on the home page. I have created one User table that works according to AuthLogic's example app at http://github.com/binarylogic/authlogic_example. I have added a field called "User Type" that currently contains either 'Customer', 'Company', or 'Vendor'. Note: each user type contains many disparate fields so I'm not sure if Single Table Inheritance is the best way to go (would welcome corrections if this conclusion is invalid). Is this a polymorphic association where each of the three types is 'tagged' with a User record? How should my models look so I have the right relationships between my User table and my user types Customer, Company, Vendor? Thanks very much!

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• Actionscript 3 Sprite AddChild

  - by Amy

  Im new to actionscript 3 and am a little confused about how the addchild function works. I want to draw 5 houses. each house has a roof and wall. Each wall has a door and a window. I have the following classes and this is how I grouped them class Main class House class Roof //a triangle class Wall //a rectangle class Door //a rectangle class Window //a square Im having trouble with inheritance of the classes. I cant made the wall class show up with a window and a door. Can someone point me to the right direction?

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• Rails STI: SuperClass Model Methods called from SubClass

  - by Karl

  I would like a little confirmation that I'm doing this correctly. Using rails single table inheritance I have the following models and class method: class PhoneNumber < ActiveRecord::Base def self.qual?(number) klass = self klass.exists?(:phone_number => phone_number) end end class Bubba < PhoneNumber end class Rufus < PhoneNumber end Bubba.qual?("8005551212") Tests pass and everything seems to work properly in rails console. Just wanted to confirm that I'm not headed for future trouble by using self in the superclass PhoneNumber and using that to execute class methods on subclasses from the parent. Is there a better way?

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• const correctness

  - by ra170

  I was going through: C++ FAQs about inheritance and decided to implement it (just to learn it) #include "Shape.h" void Shape::print() const { float a = this->area(); // area() is pure virtual ... } now, everything (well, almost) works as described in item: faq:23.1 except that print() is const and so it can't access the "this" pointer, as soon as you take out const, it works. Now, C++ FAQs have been around for a while and are usually pretty good. Is this a mistake? Do they have typo or am I wrong? If I'm wrong, I would like to know how is it possible to access the "this" pointer in a const function.

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• Testing complex entities

  - by Carlos

  I've got a C# form, with various controls on it. The form controls an ongoing process, and there are many, many aspects that need to be right for the program to run correctly. Each part can be unit tested (for instance, loading some coefficients, drawing some diagnostics) but I often run into problems that are best described with an example: "If I click here, then here, then change this, then re-open the form, then click here, it crashes or produces an error" I've tried my best to use common code organisational ideas (inheritance, DRY, separation of concerns) but there never seems to be a way to test every single path, and inevitably, a form with several controls will have a huge number of ways to execute. What can I read (preferably online) that addresses this kind of issue, and is there a (non-generic) term for it. This isn't a specific problem I'm having, but one that creeps up on me, especially with WinForms.

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• Adding Java packages to GWT

  - by Organiccat

  I've tried searching but couldn't come up with a defined way on how to add your own packages to a GWT project. My tree structure looks like this: -com.mycompany -public MyApplication.html MyApplication.gwt.xml -com.mycompany.client MyApp.java -com.mycompany.gui TableLayout.java The answer I've seen out there says to add the packages relative to the root directory of the gwt.xml file, like so: <module> <inherits name="com.google.gwt.user.User" /> <entry-point class="com.mycompany.client.MyApp" /> <source path="client" /> <source path="gui" /> </module> It then complains: Unable to find type 'com.technicon.client.MyApp' Hint: Previous compiler errors may have made this type unavailable Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly Can anyone tell me what I'm doing wrong and how to fix this?

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• screen orientation problem in windows mobile application

  - by karim

  some one in tips and tricks say like this plz i cant understand that plz if u could provide saple code for that answer ,i could understand it.actullay iam facing this problem in my application where iam using C#.net,VS 2008,windows mobile 6 professional. they told like this below one If you have to support multiple screen sizes/resolutions, form inheritance is an excellent way to do it. Basically you design your form to fit the standard 320x240 screen. To support a different screen size, you just add a new form, inherit from your custom form (instead of just Form), and then re-arrange the controls as necessary.

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• Identifying NHibernate proxy classes

  - by Marc Gravell

  I'm not an NHibernate user; I write a serialization utility library. A user has logged a feature-request that I should handle NHibernate proxy classes, treating them the same as the actual type. At the moment my code is treating them as unexpected inheritance, and throwing an exception. The code won't know in advance about NHibernate (including no reference, but I'm not aftaid of reflection ;-p) Is there a robust / guaranteed way of detecting such proxy types? Apparently DataContractSerializer handles this fine, so I'm hoping it is something pretty simple. Perhaps some interface or [attribute] decoration. Also, during deserialization; at the moment I would be creating the original type (not the NHibernate type). Is this fine for persistence purposes? Or is the proxy type required? If the latter; what is required to create an instance of the proxy type?

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• Looking for a better way to integrate a static list into a set of classes

  - by EvilTeach

  I'm trying to expand my sons interest from Warcraft 3 programming into C++ to broaden his horizons to a degree. We are planning on porting a little game that he wrote. The context goes something like this. There are Ships and Missiles, for which Ships will use Missiles and interact with them A Container exists which will hold 'a list' of ships. A Container exists which will hold 'a list' of planets. One can apply a function over all elements in the Container (for_each) Ships and Missles can be created/destroyed at any time New objects automatically insert themselves into the proper container. I cobbled a small example together to do that job, so we can talk about topics (list, templates etc) but I am not pleased with the results. #include <iostream> #include <list> using namespace std; /* Base class to hold static list in common with various object groups */ template<class T> class ObjectManager { public : ObjectManager ( void ) { cout << "Construct ObjectManager at " << this << endl; objectList.push_back(this); } virtual ~ObjectManager ( void ) { cout << "Destroy ObjectManager at " << this << endl; } void for_each ( void (*function)(T *) ) { for (objectListIter = objectList.begin(); objectListIter != objectList.end(); ++objectListIter) { (*function)((T *) *objectListIter); } } list<ObjectManager<T> *>::iterator objectListIter; static list<ObjectManager<T> *> objectList; }; /* initializer for static list */ template<class T> list<ObjectManager<T> *> ObjectManager<T>::objectList; /* A simple ship for testing */ class Ship : public ObjectManager<Ship> { public : Ship ( void ) : ObjectManager<Ship>() { cout << "Construct Ship at " << this << endl; } ~Ship ( void ) { cout << "Destroy Ship at " << this << endl; } friend ostream &operator<< ( ostream &out, const Ship &that ) { out << "I am a ship"; return out; } }; /* A simple missile for testing */ class Missile : public ObjectManager<Missile> { public : Missile ( void ) : ObjectManager<Missile>() { cout << "Construct Missile at " << this << endl; } ~Missile ( void ) { cout << "Destroy Missile at " << this << endl; } friend ostream &operator<< ( ostream &out, const Missile &that ) { out << "I am a missile"; return out; } }; /* A function suitable for the for_each function */ template <class T> void show ( T *it ) { cout << "Show: " << *it << " at " << it << endl; } int main ( void ) { /* Create dummy planets for testing */ Missile p1; Missile p2; /* Demonstrate Iterator */ p1.for_each(show); /* Create dummy ships for testing */ Ship s1; Ship s2; Ship s3; /* Demonstrate Iterator */ s1.for_each(show); return 0; } Specifically, The list is effectively embedded in each ship though the inheritance mechanism. One must have a ship, in order to access the list of ships. One must have a missile in order to be able to access the list of missiles. That feels awkward. My question boils down to "Is there a better way to do this?" Automatic object container creation Automatic object insertion Container access without requiring an object in the list to access it. I am looking for better ideas. All helpful entries get an upvote. Thanks Evil.

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• Hook for redraw event in Blackberry

  - by Bendlas

  Is there a way to add a redraw callback to a live screen object, i.e. not via inheritance? Reasoning: I want to draw an overlay from an extension for widget sdk (substituting defunct position:absolute), so the screen is created by the bbwp stub. I can get it by Ui.getUiEngine().getActiveScreen() and draw on it quite nicely, but I need a way to redraw when appropriate. Note: I've abandoned the approach to push the overlay as a screen, because i couldn't make it transparent / find a way to pass events through.

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• how can I implement Comparable more than once?

  - by codeman73

  I'm upgrading some code to Java 5 and am clearly not understanding something with Generics. I have other classes which implement Comparable once, which I've been able to implement. But now I've got a class which, due to inheritance, ends up trying to implement Comparable for 2 types. Here's my situation: I've got the following classes/interfaces: interface Foo extends Comparable<Foo> interface Bar extends Comparable<Bar> abstract class BarDescription implements Bar class FooBar extends BarDescription implements Foo With this, I get the error 'interface Comparable cannot be implemented more than once with different arguments...' Why can't I have a compareTo(Foo foo) implemented in FooBar, and also a compareTo(Bar) implemented in BarDescription? Isn't this simply method overloading?

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• What is the motivation behind "Use Extension Methods Sparingly?"

  - by Robert Harvey

  I find them a very natural way to extend existing classes, especially when you just need to "spot-weld" some functionality onto an existing class. Microsoft says, "In general, we recommend that you implement extension methods sparingly and only when you have to." And yet extension methods form the foundation of Linq; in fact, Linq was the reason extension methods were created. Are there specific design criteria where using extension methods are perferred over inheritance or composition? Under what criteria are they discouraged?

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• ASP.NET MVC UpdateModel - fields vs properties??

  - by mrjoltcola

  I refactored some common properties into a base class and immediately my model updates started failing. UpdateModel() and TryUpdateModel() did not seem to update inherited public properties. I cannot find detailed info on MSDN nor Google as to the rules or semantics of these methods. The docs are terse (http://msdn.microsoft.com/en-us/library/dd470933.aspx), simply stating: Updates the specified model instance using values from the controller's current value provider. SOLVED: MVC.NET does indeed handle inherited properties just fine. This turned out to have nothing to do with inheritance. My base class was implemented with public fields, not properties. Switching them to formal properties (adding {get; set; }) was all I needed. This has bitten me before, I keep wanting to use simple, public fields. I would argue that fields and properties are syntactically identical, and could be argued to be semantically equivalent, for the user of the class.

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• How do I make a simple image-based button with visual states in Silverlight 3?

  - by Jacob

  At my previous company, we created our RIAs using Flex with graphical assets created in Flash. In Flash, you could simply lay out your graphics for different states, i.e. rollover, disabled. Now, I'm working on a Silverlight 3 project. I've been given a bunch of images that need to serve as the graphics for buttons that have a rollover, pressed, and normal state. I cannot figure out how to simply create buttons with different images for different visual states in Visual Studio 2008 or Expression Blend 3. Here's where I am currently. My button is defined like this in the XAML: <Button Style="{StaticResource MyButton}"/> The MyButton style appears as follows: <Style x:Key="MyButton" TargetType="Button"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="Button"> <Image Source="/Assets/Graphics/mybtn_up.png" Width="54" Height="24"> <VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="FocusStates"> <VisualState x:Name="Focused"/> <VisualState x:Name="Unfocused"/> </VisualStateGroup> <VisualStateGroup x:Name="CommonStates"> <VisualState x:Name="Normal"/> <VisualState x:Name="MouseOver"/> <VisualState x:Name="Pressed"/> <VisualState x:Name="Disabled"/> </VisualStateGroup> </VisualStateManager.VisualStateGroups> </Image> </ControlTemplate> </Setter.Value> </Setter> </Style> I cannot figure out how to assign a different template to different states, nor how to change the image's source based on which state I'm in. How do I do this? Also, if you know of any good documentation that describes how styles work in Silverlight, that would be great. All of the search results I can come up with are frustratingly unhelpful. Edit: I found a way to change the image via storyboards like this: <Style x:Key="MyButton" TargetType="Button"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="Button"> <Image Source="/Assets/Graphics/mybtn_up.png" Width="54" Height="24" x:Name="Image"> <VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="FocusStates"> <VisualState x:Name="Focused"/> <VisualState x:Name="Unfocused"/> </VisualStateGroup> <VisualStateGroup x:Name="CommonStates"> <VisualState x:Name="Normal"/> <VisualState x:Name="MouseOver"> <Storyboard Storyboard.TargetName="Image" Storyboard.TargetProperty="Source"> <ObjectAnimationUsingKeyFrames> <DiscreteObjectKeyFrame KeyTime="0" Value="/Assets/Graphics/mybtn_over.png"/> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> <VisualState x:Name="Pressed"> <Storyboard Storyboard.TargetName="Image" Storyboard.TargetProperty="Source"> <ObjectAnimationUsingKeyFrames> <DiscreteObjectKeyFrame KeyTime="0" Value="/Assets/Graphics/mybtn_active.png"/> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> <VisualState x:Name="Disabled"/> </VisualStateGroup> </VisualStateManager.VisualStateGroups> </Image> </ControlTemplate> </Setter.Value> </Setter> </Style> However, this seems like a strange way of doing things to me. Is there a more standard way of accomplishing this?

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• Functional languages targeting the LLVM

  - by Matthew

  Are there any languages that target the LLVM that: Are statically typed Use type inference Are functional (i.e. lambda expressions, closures, list primitives, list comprehensions, etc.) Have first class object-oriented features (inheritance, polymorphism, mixins, etc.) Have a sophisticated type system (generics, covariance and contravariance, etc.) Scala is all of these, but only targets the JVM. F# (and to some extent C#) is most if not all of these, but only targets .NET. What similar language targets the LLVM?

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• Symfony 1.3 and forms: the password changes when i click on 'Save', why??

  - by user248959

  Hi, i have installed sfDoctrineGuardUser and have created this model that inherits sfGuardUser model: Usuario: inheritance: extends: sfGuardUser type: simple columns: nombre_apellidos: string(60) sexo: boolean fecha_nac: date provincia: string(60) localidad: string(255) email_address: string(255) avatar: string(255) avatar_mensajes: string(255) I have also created a module called 'miembros' based on that model. Well, I log normally through sfGuardAuth/signin, then i go to "miembros/edit/id/$id_of_the_member_i_used_to_log_in" and push 'Save' button. Then i logout. If i try to log in again, it says: "The username and/or password is invalid". Later, i have realized that when click 'Save' the value of the field 'password' changes (well its encrypted version). So that is the reason why i can not then log in. But, why the value of the password change when i click on 'Save' ??? Regards Javi

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• gwt compiling error

  - by Hoax

  Compiling module com.sem.Sem10 Finding entry point classes [ERROR] Unable to find type 'com.sem.client.Sem10' [ERROR] Hint: Previous compiler errors may have made this type unavailable [ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly My package structure is com.sem com.sem.client com.sem.schema com.sem.server inherits name='com.google.gwt.user.User' inherits name='com.google.gwt.user.theme.standard.Standard' inherits name='com.google.gwt.maps.GoogleMaps' script src="http://maps.google.com/maps?gwt=1&file=api&amp.... entry-point class='com.sem.client.Sem10' source path='com.sem.schema' I have googled this thing for quite a while and could not find a solution...? any help appreciated

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• Managing Strategy objects with Hibernate & Spring

  - by Francois

  This is a design question better explained with a Stack Overflow analogy: Users can earn Badges. Users, Badges and Earned Badges are stored in the database. A Badge’s logic is run by a Badge Condition Strategy. I would prefer not to have to store Badge Condition Strategies in the database, because they are complex tree structure objects. How do I associate a Badge stored in the database with its Badge Condition Strategy? I can only think of workaround solutions. For example: create 1 class per badge and use a SINGLE_TABLE inheritance strategy. Or get the badge from the database, and then programmatically lookup and inject the correct Badge Condition Strategy. Thanks for suggesting a better design.

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• Authlogic auto login fails on registration with STI User model

  - by Wei Gan

  Authlogin by default is supposed to auto login when the user's persistence token changes. It seems to fail in my Rails app. I set up the following single table inheritance user model hierarchy: class BaseUser < ActiveRecord::Base end class User < BaseUser acts_as_authentic end create_table "base_users", :force => true do |t| t.string "email" t.string "crypted_password" t.string "persistence_token" t.string "first_name" t.string "last_name" t.datetime "created_at" t.datetime "updated_at" t.string "type" end To get auto login to work, I need to explicitly log users in in my UsersController: def create @user = User.new(params[:user]) if @user.save UserSession.create(@user) # EXPLICITLY LOG USER IN BY CREATING SESSION flash[:notice] = "Welcome to Askapade!" redirect_to_target_or_default root_url else render :action => :new end end I was wondering if it's anything to do with STI, or that the table is named "base_users" and not "users". I set it up before without STI and it worked so I'm wondering why once I put in place this hierarchy, it fails. Thanks!

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• PHP Doctrine - YAML syntax help. Default value for many to many relationship?

  - by Dan

  Hi, I have the following YAML schema for organising users in Doctrine: Person: tableName: people columns: id: type: integer primary: true autoincrement: true firstname: type: string notnull: true lastname: type: string notnull: true User: inheritance: extends: Person type: column_aggregation keyField: type keyValue: 1 Userdetails: columns: person_id: type: integer primary: true password: type: string notnull: true relations: User: foreignType: one local: person_id onDelete: CASCADE onUpdate: CASCADE Group: tableName: groups columns: id: type: integer primary: true autoincrement: true name: type: string notnull: true UserGroup: columns: group_id: type: integer primary: true person_id: type: integer primary: true relations: User: foreignType: many local: person_id Group: foreignType: many Basically, any people who are users will belong to one or more groups. Is there any way to add new users to a particular group by default? Any advice appreciated. Thanks

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• How to provide Input to Dialogs designed by Qt Designer

  - by GG

  Hello, I am a Qt beginner and working with Qt Designer to develop some small UI elements. I read http://doc.trolltech.com/4.5/designer-using-a-ui-file.html to use these GUI elements in my code and using multiple inheritance approach. I am introducing bookmark feature which somewhat look like http://img293.imageshack.us/img293/3041/screenshotyb.png. Now the problem I am facing is How can I show all existing bookmark folders in the drop down(say folders are in a QVector). So my main problem is how can I pass some inputs to the UI element. I think I'm clear, please let me know if further explanation is required. Sorry for adding links directly, rich formatting in my browser is not working. Thanks in advance,

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• Rails Full Engine using a Full Engine

  - by SirLenz0rlot

  I've got this full rails engine Foo with functionality X. I want to make another engine, engine Bar, that is pretty much the same, but override funcitonality x with y. (it basically does the same, but a few controller actions and views are differently implemented). (I might split this later in several mountable engines, but for now, this will be the setup: project Baz, using engine Bar, which uses engine Foo) I would like to know if there are any pitfalls. It doesn't seem like a pattern that is often used? Anybody else using this 'some sort of engine inheritance'?

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• How do I fix "error 1004, 0, Unable to find property" in an Entity Framework 4 WinForms application?

  - by Ivan

  I've designed an EF4 model (quite complex inheritance, lots of small tables incl. multiple self-referencing), generated (table-per-type) a database and inserted some basic data manually. It works fine in an ASP.Net Dynamic Data Entities web application with full automatic scaffolding. But when in a WinForms application using the same model (I share it as a part of a class library) I construct a query and bind a combo box to it (the way it's shown here), I get an InnerException {"Internal .NET Framework Data Provider error 1004, 0, Unable to find property... I've found a question about the same problem here (incl. a sample to reproduce the error) but no answer. I use final Visual Studio 2010, no beta.

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• Link objects as fields in UML diagram

  - by fearofawhackplanet

  I'm trying to generate a diagram for a design document. I've generated a class diagram in VS. At the moment it's just a bunch of unconnected boxes as there isn't any inheritance going on. It feels like it would be more useful if I could show how the objects interact through properties and parameters. As an example, a Boy class has a method Kiss which takes a Girl object. How can I show that Boy and Girl interact by connecting this in the diagram? Is there a notation for this in UML? Or is there another type of diagram that shows this? Can I make VS draw this connection for me somehow? Or is this a silly/useless idea? It just doesn't feel like a proper diagram unless it's got some lines on it somewhere :)

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• Asp .Net MVC Viewmodel should be class or struct?

  - by Jonas Everest

  Hey guys, I have just been thinking about the concept of view model object we create in asp.net MVC. Our purpose is to instantiate it and pass it from controller to view and view read it and display the data. Those view model are usually instantiated through constructor. We won't need to initialize the members, we may not need to redefine/override parameterless constructor and we don't need inheritance feature there. So, why don't we use struct type for our view model instead of class. It will enhance the performance.

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