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  • How do I model teams and gameplay in this scorekeeping application?

    - by Eric Hill
    I'm writing a scorekeeping application for card game that has a few possibly-interesting constraints. The application accepts user registrations for players, then lets them check-in to a particular game (modeled as Event). After the final player registers, the app should generate teams, singles or doubles, depending on the preference of the person running the game and some validations (can't do doubles if there's an odd number checked in). There are @event.teams.count rounds in the game. To sum up: An event consists of `@event.teams.count` rounds; Teams can have 1 or more players Events have n or n/2 teams (depending on whether it's singles or doubles) Users will be members of different teams at different events Currently I have a rat's nest of associations: class User < ActiveRecord::Base has_many :teams, :through => :players has_many :events, :through => :teams class Event < ActiveRecord::Base has_many :rounds has_many :teams has_many :players, :through => :teams class Player < ActiveRecord::Base belongs_to :user belongs_to :team end class Team < ActiveRecord::Base has_many :players belongs_to :event end class Round < ActiveRecord::Base belongs_to :event belongs_to :user end The sticky part is team generation. I have basically a "start game" button that should freeze the registrations and pair up teams either singly or doubly, and render to Round#new so that the first (and subsequent) matches can be scored. Currently I'm implementing this as a check on Round#new that calls Event#generate_teams and displays the view: # Event#generate_teams def generate_teams # User has_many :events, :through => :registrations # self.doubles is a boolean denoting 2 players per team registrations.in_groups_of(self.doubles ? 2 : 1, nil).each do |side| self.teams << Player.create(self,side) end end Which doesn't work. Should there maybe be a Game model that ties everything together rather than (my current method) defining the game as an abstraction via the relationships between Events, Users, and Rounds (and Teams and Players and etc.)? My head is swimming.

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  • $stdin compatibility with std::istream using swig, C++, and Ruby

    - by Kenny Peng
    I have a function in C++ that takes in an std::istream as the input: class Foo { Foo(std::istream &); } Using SWIG, I've bound it to Ruby, but Ruby's $stdin variable is fundamentally different from anything like the stream classes in C++, so I'm not sure how to either 1) expose the C++ class to Ruby in a way that I can use $stdin, or 2) convert $stdin into something the C++ class can understand. Anyone have experience with binding iostreams in C++ to Ruby? Thanks.

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  • Way to get VS 2008 to stop forcing indentation on namespaces?

    - by Earlz
    I've never really been a big fan of the way most editors handle namespaces. They always force you to add an extra pointless level of indentation. For instance, I have a lot of code in a page that I would much rather prefer formatted as namespace mycode{ class myclass{ void function(){ foo(); } void foo(){ bar(); } void bar(){ //code.. } } } and not something like namespace mycode{ class myclass{ void function(){ foo(); } void foo(){ bar(); } void bar(){ //code.. } } } Honestly, I don't really even like the class thing being indented most of the time because I usually only have 1 class per file. And it doesn't look as bad here, but when you get a ton of code and lot of scopes, you can easily have indentation that forces you off the screen, and plus here I just used 2-space tabs and not 4-space as is used by us. Anyway, is there some way to get Visual Studio to stop trying to indent namespaces for me like that?

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  • [C++]Advantage of using a static member function instead of an equivalent non-static member function

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • Using Spring as a JPA Container

    - by sdoca
    Hi, I found this article which talks about using Spring as a JPA container: http://java.sys-con.com/node/366275 I have never used Spring before this and am trying to make this work and hope someone can help me. In the article it states that you need to annotate a Spring bean with @Transactional and methods/fields with @PersistenceContext in order to provide transaction support and to inject an entity manager. Is there something the defines a bean as a "Spring Bean"? I have a bean class which implements CRUD operations on entities using generics: @Transactional public class GenericCrudServiceBean implements GenericCrudService { @PersistenceContext(unitName="MyData") private EntityManager em; @Override @PersistenceContext public <T> T create(T t) { em.persist(t); return t; } @Override @PersistenceContext public <T> void delete(T t) { t = em.merge(t); em.remove(t); } ... ... ... @Override @PersistenceContext public List<?> findWithNamedQuery(String queryName) { return em.createNamedQuery(queryName).getResultList(); } } Originally I only had this peristence context annotation: @PersistenceContext(unitName="MyData") private EntityManager em; but had a null em when findWithNamedQuery was invoked. Then I annotated the methods as well, but em is still null (no injection?). I was wondering if this had something to do with my bean not being recognized as "Spring". I have done configuration as best I could following the directions in the article including setting the following in my context.xml file: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns:tx="http://www.springframework.org/schema/tx" tx:schemaLocation="http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd"> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitName" value="MyData" /> <property name="dataSource" ref="dataSource" /> <property name="loadTimeWeaver" class="org.springframework.classloading.ReflectiveLoadTimeWeaver" /> <property name="jpaVendorAdapter" ref="jpaAdapter" /> </bean> <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" /> <property name="url" value="jdbc:oracle:thin:@localhost:1521:MySID" /> <property name="username" value="user" /> <property name="password" value="password" /> <property name="initialSize" value="3" /> <property name="maxActive" value="10" /> </bean> <bean id="jpaAdapter" class="org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter"> <property name="databasePlatform" value="org.eclipse.persistence.platform.database.OraclePlatform" /> <property name="showSql" value="true" /> </bean> <bean class="org.springframework.ormmjpa.support.PersistenceAnnotationBeanPostProcessor" /> <tx:annotation-driven /> </beans> I guessed that these belonged in the context.xml file because the article never specifically said which file is the "application context" file. If this is wrong, please let me know.

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  • jquery tablesorter problem in FF only - header row disappears after show-hide of rows

    - by dac
    When the page loads, all the records show. Sorting works great until show-hide is used to filter the rows so only some show. Then the header row--with the arrows for sorting--DISAPPEARS. The problem is only in Firefox. It works great in IE7 and IE8. I'm using jQuery 1.4.2 from google. Code for show-hide $(document).ready(function() { // show all the rows $("#org_status tr").show(); //find selected filter $("#filter_status a").click(function(evt) { evt.preventDefault(); $("#org_status tr").hide(); var id = $(this).attr('id'); $("." + id).show(); }); }); Here is the HTML: <!-- show-hide "buttons" --> <p id='filter_status'>Filter by status: <a href='#' id='All'>All</a> <a href='#' id='Active'>Active</a> <a href='#' id='Inactive'>Inactive</a> <a href='#' id='Pending'>Pending</a> </p> <!-- table to sort -> <table id='org_status' class='info_table tablesorter'> <thead> <tr> <th class='org-name-col'>Name</th> <th class='org-status-col'>Status</th> </tr> </thead> <tbody> <tr class='All Active'> <td><a href='admin/org_edit.php?org=29'>Foo Net</a></td> <td>Active</td>"; </tr> <tr class='All Inactive'> <td><a href='admin/org_edit.php?org=22'>Bar</a></td> <td>Active</td>"; </tr> <tr class='All Pending'> <td><a href='admin/org_edit.php?org=11'> Bar Foo Very Long Org Name Goes Here</a></td> <td>Active</td>"; </tr> </tbody> </table>

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  • Singleton Properties

    - by coffeeaddict
    Ok, if I create a singleton class and expose the singleton object through a public static property...I understand that. But my singleton class has other properties in it. Should those be static? Should those also be private? I just want to be able to access all properties of my singleton class by doing this: MySingletonClass.SingletonProperty.SomeProperty2 Where SingletonProperty returns me the single singleton instance. I guess my question is, how do you expose the other properties in the singleton class..make them private and then access them through your public singleton static property?

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  • Adding DataAnnontations to Generated Partial Classes

    - by Naz
    Hi I have a Subsonic3 Active Record generated partial User class which I've extended on with some methods in a separate partial class. I would like to know if it is possible to add Data Annotations to the member properties on one partial class where it's declared on the other Subsonic Generated one I tried this. public partial class User { [DataType(DataType.EmailAddress, ErrorMessage = "Please enter an email address")] public string Email { get; set; } ... } That examples gives the "Member is already defined" error. I think I might have seen an example a while ago of what I'm trying to do with Dynamic Data and Linq2Sql.

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  • question on database query using hibernate in java with annotations

    - by molleman
    Hello, simple question regarding HQL(Hibernate query language) so i have user class , that can hold a list of Projects, how do i take this out of the database depending on a username, this is how i take out my user String username = "stephen"; YFUser user = (YFUser) session.createQuery("select u FROM YFUser u where u.username = :username").setParameter("username", name).uniqueResult(); but i want to take out the list of projects here is the projects list within the class YFUser(my user class); how would i query the database to get this list of projects @Entity @Table(name = "yf_user_table") public class YFUser implements Serializable,ILightEntity { ......... @OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY) @JoinTable(name = "YFUSER_JOIN_PROJECT", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "project_id") }) private List<Project> projects = new ArrayList<Project>();

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  • C++ Multiple inheritance with interfaces?

    - by umanga
    Greetings all, I come from Java background and I am having difficulty with multiple inheritance. I have an interface called IView which has init() method.I want to derive a new class called PlaneViewer implementing above interface and extend another class. (QWidget). My implementation is as: IViwer.h (only Header file , no CPP file) : #ifndef IVIEWER_H_ #define IVIEWER_H_ class IViewer { public: //IViewer(); ///virtual //~IViewer(); virtual void init()=0; }; #endif /* IVIEWER_H_ */ My derived class. PlaneViewer.h #ifndef PLANEVIEWER_H #define PLANEVIEWER_H #include <QtGui/QWidget> #include "ui_planeviewer.h" #include "IViewer.h" class PlaneViewer : public QWidget , public IViewer { Q_OBJECT public: PlaneViewer(QWidget *parent = 0); ~PlaneViewer(); void init(); //do I have to define here also ? private: Ui::PlaneViewerClass ui; }; #endif // PLANEVIEWER_H PlaneViewer.cpp #include "planeviewer.h" PlaneViewer::PlaneViewer(QWidget *parent) : QWidget(parent) { ui.setupUi(this); } PlaneViewer::~PlaneViewer() { } void PlaneViewer::init(){ } My questions are: Is it necessary to declare method init() in PlaneViewer interface also , because it is already defined in IView? 2.I cannot complie above code ,give error : PlaneViewer]+0x28): undefined reference to `typeinfo for IViewer' collect2: ld returned 1 exit status Do I have to have implementation for IView in CPP file?

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  • Regular expressions - finding and comparing the first instance of a word

    - by Dan
    Hi there, I am currently trying to write a regular expression to pull links out of a page I have. The problem is the links need to be pulled out only if the links have 'stock' for example. This is an outline of what I have code wise: <td class="prd-details"> <a href="somepage"> ... <span class="collect unavailable"> </td> <td class="prd-details"> <a href="somepage"> ... <span class="collect available"> </td> What I would like to do is pull out the links only if 'collect available' is in the tag. I have tried to do this with the regular expression: (?s)prd-details[^=]+="([^"]+)" .+?collect{1}[^\s]+ available However on running it, it will find the first 'prd-details' class and keep going until it finds 'collect available', thereby taking the incorrect results. I thought by specifying the {1} after the word collect it would only use the first instance of the word it finds, but apparently I'm wrong. I've been trying to use different things such as positive and negative lookaheads but I cant seem to get anything to work. Might anyone be able to help me with this issue? Thanks, Dan

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  • Problems with listening an event in child object in Actionscript

    - by Raigomaru
    I have two classes. The first one (the starting class): package { import flash.display.Sprite; import flash.events.KeyboardEvent; import tetris.*; public class TetrisGame extends Sprite { private var _gameWell:Well; public function TetrisGame() { _gameWell = new Well(); addChild(_gameWell); } } } The second: package tetris { import flash.display.Sprite; import flash.events.KeyboardEvent; public class Well extends Sprite { public function Well() { super(); addEventListener(KeyboardEvent.KEY_DOWN, onKeyboard); } private function onKeyboard(event:KeyboardEvent):void { //some code is here } } } But when I press any buttons on my keyboard, the child class Well doesn't have any reaction. What's the problem?

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  • Solution Items in Visual Studio 2005/2008

    - by Muneeb
    Is it possible to add a class as a solution item and use it as a linked item in all the projects in the solution? Basically I was thinking of creating a class (which will inherit ConfigurationSection) and keeping it as the Solution Item. I wanted to add it as a linked item in all the projects in the solution, so that everyone can use it to access the configuration properties. (Refer to this tutorial for more details) Now the issue I am facing is that when I create a class in the solution item, it doesn't have any namespace. And it shows up in intellisense, inside the projects but once I create an object of the solution item class, the object doesn't show up in intellisense. Any ideas why?

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  • finding highlighted(preselcted) text using xpath or css

    - by doneright
    In following 2 snippets of html code, I'm trying to create xpath or css for finding if span(Element1 in snippet 1 and Element 2 in snippet 2) are highlighted(preselected) when page is loaded <div id="idc" class="tre"> <ul id="idCatT_srt_ul" class="abc"> <li class="treN treB treSelected" title="Element1 title"> <span class="spclass">Element1</span> </li> </ul> </div> Element 2 Text

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  • how to insert a new li tag at the specified lication?

    - by Amit
    Hi I wanted to insert a li tag in the middle of a list of li tags based on a css class set to the li tag using jQuery. Consider the following <ul class="myList"> <li><a href="#">test 1</a></li> <li class="active"><a href="#">test 2</a></li> <li><a href="#">test 3</a></li> <li><a href="#">test 4</a></li> <li><a href="#">test 5</a></li> <li><a href="#">test 6</a></li> </ul> I wanted to insert a new li tag after the li tag set to active. So the output will be like this. <ul class="myList"> <li><a href="#">test 1</a></li> <li class="active"><a href="#">test 2</a></li> <li><a href="#">My new Tag</a></li> <li><a href="#">test 3</a></li> <li><a href="#">test 4</a></li> <li><a href="#">test 5</a></li> <li><a href="#">test 6</a></li> </ul> I tried with .appendTo, .insertAfter, .append etc. but could not get the result I wanted. Any idea how this can be achieved?

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  • Python C API from C++ app - know when to lock

    - by Alex
    Hi Everyone, I am trying to write a C++ class that calls Python methods of a class that does some I/O operations (file, stdout) at once. The problem I have ran into is that my class is called from different threads: sometimes main thread, sometimes different others. Obviously I tried to apply the approach for Python calls in multi-threaded native applications. Basically everything starts from PyEval_AcquireLock and PyEval_ReleaseLock or just global locks. According to the documentation here when a thread is already locked a deadlock ensues. When my class is called from the main thread or other one that blocks Python execution I have a deadlock. Python Cfunc1() - C++ func that creates threads internally which lead to calls in "my class", It stuck on PyEval_AcquireLock, obviously the Python is already locked, i.e. waiting for C++ Cfunc1 call to complete... It completes fine if I omit those locks. Also it completes fine when Python interpreter is ready for the next user command, i.e. when thread is calling funcs in the background - not inside of a native call I am looking for a workaround. I need to distinguish whether or not the global lock is allowed, i.e. Python is not locked and ready to receive the next command... I tried PyGIL_Ensure, unfortunately I see hang. Any known API or solution for this ? (Python 2.4)

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  • Is it possible to order by a composite key with JPA and CriteriaBuilder

    - by Kjir
    I would like to create a query using the JPA CriteriaBuilder and I would like to add an ORDER BY clause. This is my entity: @Entity @Table(name = "brands") public class Brand implements Serializable { public enum OwnModeType { OWNER, LICENCED } @EmbeddedId private IdBrand id; private String code; //bunch of other properties } Embedded class is: @Embeddable public class IdBrand implements Serializable { @ManyToOne private Edition edition; private String name; } And the way I am building my query is like this: CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<Brand> q = cb.createQuery(Brand.class).distinct(true); Root<Brand> root = q.from(Brand.class); if (f != null) { f.addCriteria(cb, q, root); f.addOrder(cb, q, root, sortCol, ascending); } return em.createQuery(q).getResultList(); And here are the functions called: public void addCriteria(CriteriaBuilder cb, CriteriaQuery<?> q, Root<Brand> r) { } public void addOrder(CriteriaBuilder cb, CriteriaQuery<?> q, Root<Brand> r, String sortCol, boolean ascending) { if (ascending) { q.orderBy(cb.asc(r.get(sortCol))); } else { q.orderBy(cb.desc(r.get(sortCol))); } } If I try to set sortCol to something like "id.edition.number" I get the following error: javax.ejb.EJBException: java.lang.IllegalArgumentException: Unable to resolve attribute [id.name] against path Any idea how I could accomplish that? I tried searching online, but I couldn't find a hint about this... Also would be great if I could do a similar ORDER BY when I have a @ManyToOne relationship (for instance, "id.edition.number")

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  • instantiate spring bean via factory method

    - by Don
    Hi, I need to instantiate a Spring bean in the same manner as this Java code: MyClass foo = Mockito.mock(MyClass.class); The XML I need will look something like: <bean id="foo" class="Mockito" factory-method="mock"> <constructor-arg value="MyClass"/> </bean> I can't seem to find the correct syntax for passing a Class object as a parameter to the factory method. Thanks, Don

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  • Android, how to use DexClassLoader to dynamically replace an Activity or Service

    - by RickNotFred
    I am trying to do something similar to this stackoverflow posting. What I want to do is to read the definition of an activity or service from the SD card. To avoid manifest permission issues, I create a shell version of this activity in the .apk, but try to replace it with an activity of the same name residing on the SD card at run time. Unfortunately, I am able to load the activity class definition from the SD card using DexClassLoader, but the original class definition is the one that is executed. Is there a way to specify that the new class definition replaces the old one, or any suggestions on avoiding the manifest permission issues without actually providing the needed activity in the package? The code sample: ClassLoader cl = new DexClassLoader("/sdcard/mypath/My.apk", getFilesDir().getAbsolutePath(), null, MainActivity.class.getClassLoader()); try { Class<?> c = cl.loadClass("com.android.my.path.to.a.loaded.activity"); Intent i = new Intent(getBaseContext(), c); startActivity(i); } catch (Exception e) { Intead of launching the com.android.my.path.to.a.loaded.activity specified in /sdcard/mypath/My.apk, it launches the activity statically loaded into the project.

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  • Multiple Submit Buttons problem in Struts2

    - by umesh awasthi
    Hi All, Trying to work with multiple submit buttons within a single form in struts2 application but not able to work. here is the jsp code i am using <tr> <td class="button"><input type="submit" value="Import" name="destinationImport" class="button"></td> <td class="button"><input type="submit" value="Export" name="destinationExport" class="button"></td> </tr> here is the java part private boolean destinationImport; private boolean destinationExport; and there respective setter and getter but i am sure is that Struts2 type convertor is having problem converting the String value to boolean do any one have idea how to achieve this Thanks in advance

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  • Cross-Forest Trust

    - by cdalley
    I am looking at testing a cross-domain trust we can have two domain controllers (with different forests and domain names) setup so we can move everyone onto the new domain. We do NOT run exchange on site and we do not have any links to O365 to AD currently. Onto the problem: I have setup two DCs in a Virtual Machine: They are on the same network 192.168.0.* The Windows 2003 server: Name: OLDSRVR "Clone" of our current Domain Controller IP: 192.168.0.1 Domain: internal.test.com The Windows 2012 server: Name: ADCTEST01 Brand new domain setup from scratch separate to internal.test.com Domain: internal.test2.com IP: 192.168.0.2 OLDSRVR can only see ADCTEST if it has dynamic IP set. If I set a static IP it cannot see it. If I try using the dynamic IP and try to join it gets to the end then complains "??The trust relationship between this workstation and the primary domain failed" Any ideas?

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  • Entity Framework looking for wrong column

    - by m.edmondson
    I'm brand new to the Entity Framework and trying to learn all it can offer. I'm currently working my way through the MVC Music Store tutorial which includes the following code: public ActionResult Browse(string genre) { // Retrieve Genre and its Associated Albums from database var genreModel = storeDB.Genres.Include("Albums") .Single(g => g.Name == genre); return View(genreModel); } as I'm working in VB I converted it like so: Function Browse(ByVal genre As String) As ActionResult 'Retrieve Genre and its Associated Albums from database Dim genreModel = storeDB.Genres.Include("Albums"). _ Single(Function(g) g.Name = genre) Return(View(genreModel)) End Function The problem is I'm getting the following exception: Invalid column name 'GenreGenreId'. Which I know is true, but I can't for the life of my work out where it's getting 'GenreGenreId' from. Probably a basic question but I'll appreciate any help in the right direction. As per requested here is the source for my classes: Album.vb Public Class Album Private _title As String Private _genre As Genre Private _AlbumId As Int32 Private _GenreId As Int32 Private _ArtistId As Int32 Private _Price As Decimal Private _AlbumArtUrl As String Public Property Title As String Get Return _title End Get Set(ByVal value As String) _title = value End Set End Property Public Property AlbumId As Int16 Get Return _AlbumId End Get Set(ByVal value As Int16) _AlbumId = value End Set End Property Public Property GenreId As Int16 Get Return _GenreId End Get Set(ByVal value As Int16) _GenreId = value End Set End Property Public Property ArtistId As Int16 Get Return _ArtistId End Get Set(ByVal value As Int16) _ArtistId = value End Set End Property Public Property AlbumArtUrl As String Get Return _AlbumArtUrl End Get Set(ByVal value As String) _AlbumArtUrl = value End Set End Property Public Property Price As Decimal Get Return _Price End Get Set(ByVal value As Decimal) _Price = value End Set End Property Public Property Genre As Genre Get Return _genre End Get Set(ByVal value As Genre) _genre = value End Set End Property End Class Genre.vb Public Class Genre Dim _genreId As Int32 Dim _Name As String Dim _Description As String Dim _Albums As List(Of Album) Public Property GenreId As Int32 Get Return _genreId End Get Set(ByVal value As Int32) _genreId = value End Set End Property Public Property Name As String Get Return _Name End Get Set(ByVal value As String) _Name = value End Set End Property Public Property Description As String Get Return _Description End Get Set(ByVal value As String) _Description = value End Set End Property Public Property Albums As List(Of Album) Get Return _Albums End Get Set(ByVal value As List(Of Album)) _Albums = value End Set End Property End Class MusicStoreEntities.vb Imports System.Data.Entity Namespace MvcApplication1 Public Class MusicStoreEntities Inherits DbContext Public Property Albums As DbSet(Of Album) Public Property Genres As DbSet(Of Genre) End Class End Namespace

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  • How to assign optional attribute of NSManagedObject in a NSManagedObjectModel having Three NSManaged

    - by Kundan
    I am using coredata framework. In my NSManagedObjectModel i am using three entities that are Class, Student and Score where class and student have one-to-many & inverse relationship and Student and Score have also inverse but one-one relationship. Score entity has all optional attributes and having default '0' decimalVaue, which is not assigned at the time new Student is added. But later i want to assign them score individually and also to particular attribute not all of score attributes in a go. I am able to create and add Students to particular Class but dont have any idea how to call particular student and assign them score. For example I want to assign Score'attribute "dribbling" [there are many attributes like "tackling"] a decimal value to Student "David" of Class "Soccer" ,how i can do that? Thanks in advance for any suggestion.

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  • Languages and VMs: Features that are hard to optimize and why

    - by mrjoltcola
    I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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  • Better to use constructor or method factory pattern?

    - by devoured elysium
    I have a wrapper class for the Bitmap .NET class called BitmapZone. Assuming we have a WIDTH x HEIGHT bitmap picture, this wrapper class should serve the purpose of allowing me to send to other methods/classes itself instead of the original bitmap. I can then better control what the user is or not allowed to do with the picture (and I don't have to copy the bitmap lots of times to send for each method/class). My question is: knowing that all BitmapZone's are created from a Bitmap, what do you find preferrable? Constructor syntax: something like BitmapZone bitmapZone = new BitmapZone(originalBitmap, x, y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.From(originalBitmap, x , y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.FromBitmap(originalBitmap, x, y, width, height); Other? Why? Thanks

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