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  • Losing data after reading them correct from file

    - by user1388172
    i have the fallowing class of object with a class a data structure which i use in main combined. The ADT(abstract data type) is a linked list. After i read from file the input data and create and object which at print looks just fine after a print. after i push_back() the 3-rd int variable get initializated to 0. So example and code: Example: ex.in: 1 7 31 2 2 2 3 3 3 now i create objects from each line, which at print look as they suppose, but after push_back(): 1 7 0 2 2 0 3 3 0 Class.h: class RAngle { private: int x,y,l,b; public: int solution,prec; RAngle(){ x = y = solution = prec = b = l =0; } RAngle(int i,int j,int k){ x = i; y = j; l = k; solution = 0; prec=0; b=0; } friend ostream& operator << (ostream& out, const RAngle& ra){ out << ra.x << " " << ra.y << " " << ra.l <<endl; return out; } friend istream& operator >>( istream& is, RAngle& ra){ is >> ra.x; is >> ra.y; is >> ra.l; return is ; } }; ADT.h: template <class T> class List { private: struct Elem { T data; Elem* next; }; Elem* first; T pop_front(){ if (first!=NULL) { T aux = first->data; first = first->next; return aux; } T a; return a; } void push_back(T data){ Elem *n = new Elem; n->data = data; n->next = NULL; if (first == NULL) { first = n; return ; } Elem *current; for(current=first;current->next != NULL;current=current->next); current->next = n; } Main.cpp(after i call this function in main which prints object as they suppose to be the x var(from RAngle class) changes to 0 in all cases.) void readData(List <RAngle> &l){ RAngle r; ifstream f_in; f_in.open("ex.in",ios::in); for(int i=0;i<10;++i){ f_in >> r; cout << r; l.push_back(r); }

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  • C# - Dictionary with generic array as value

    - by alhazen
    In my class, I want to use a dictionary with the following declaration: Dictionary<string, T[]> Since the operations of my class are exactly the same for all generic types, I do not wish to define my class as generic (which means I would have to create a separate instance of my class for each generic type I insert into the dictionary ?). One alternative I'm attempting is to use Dictionary<string, object> instead: public void Add<T>(string str, T value) { // Assuming key already exists var array = (T[]) dictionary[str]; array[0] = value; } However, when iterating over the dictionary, how do I cast the object value back to an array ? foreach(string strKey in dictionary.Keys) { var array = (T[]) dictionary[strKey]; // How to cast here ? //... array[0] = default(T); } Thanks.

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  • How do I get started writing a .Net-wrapper around C++ Omniorb-stubs

    - by Superfisi
    Hello there, my job is to access a CPRBA-server-application from .NET 3.5. After evaluating projets like IIOP.Net (undefined state) and products like VisiBroker (expensive) I'd like to do it "by myself" and write a .Net-Wrapper around C++-Stubs generated my Omniidl (the Omniorb IDL to C++ generator). This means writing some kind of layer of managed code (CLI) around the unmanaged C++ code. My question is: Has anyone experience in this topic? I honestly don't know how to do it the best way. Right now I plan to create a managed class for every unmanaged class, each managed class itself has a member to an instance of the unmanaged class, which is not garbage-collected. Is this the right way to do it or am I on the wrong path? Thanks in advance!

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  • Android: Help with tabs view

    - by James
    So I'm trying to build a tabs view for an Android app, and for some reason I get a force close every time I try to run it on the emulator. When I run the examples, everything shows fine, so I went as far as to just about copy most of the layout from the examples(a mix of Tabs2.java and Tabs3.java), but for some reason it still wont run, any ideas? Here is my code(List1.class is a copy from the examples for testing purposes). It all compiles fine, just gets a force close the second it starts: package com.jvavrik.gcm; import android.app.TabActivity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.widget.TabHost; import android.widget.TextView; public class GCM extends TabActivity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); final TabHost tabHost = getTabHost(); tabHost.addTab(tabHost.newTabSpec("tab1") .setIndicator("g", getResources().getDrawable(R.drawable.star_big_on)) .setContent(new Intent(this, List1.class))); tabHost.addTab(tabHost.newTabSpec("tab2") .setIndicator("C") .setContent(new Intent(this, List1.class)) ); tabHost.addTab(tabHost.newTabSpec("tab3") .setIndicator("S") .setContent(new Intent(this, List1.class)) ); tabHost.addTab(tabHost.newTabSpec("tab4") .setIndicator("A") .setContent(new Intent(this, List1.class)) ); } }

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  • virtual keyword in different scenarios

    - by Mahesh
    I figured out 2 different meanings for virtual based on the situation it is being used. If a baseClass has a function defined virtual, then the derivedClass is going to override the function. The baseClass::~baseClass() should be defined virtual, if there is any class derived from it. Here it means, the derived class destruction first takes place followed by base class destruction. Are there any other situations where virtual hold a different meaning ?

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  • Many-to-many mapping with LINQ

    - by Alexander
    I would like to perform LINQ to SQL mapping in C#, in a many-to-many relationship, but where data is not mandatory. To be clear: I have a news site/blog, and there's a table called Posts. A blog can relate to many categories at once, so there is a table called CategoriesPosts that links with foreign keys with the Posts table and with Categories table. I've made each table with an identity primary key, an id field in each one, if it matters in this case. In C# I defined a class for each table, defined each field as explicitly as possible. The Post class, as well as Category class, have a EntitySet to link to CategoryPost objects, and CategoryPost class has 2 EntityRef members to link to 2 objects of each other type. The problem is that a Post may relate or not to any category, as well as a category may have posts in it or not. I didn't find a way to make an EntitySet<CategoryPost?> or something like that. So when I added the first post, all went well with not a single SQL statement. Also, this post was present in the output. When I tried to add the second post I got an exception, Object reference not set to an instance of an object, regarding to the CategoryPost member. Post: [Table(Name="tm_posts")] public class Post : IDataErrorInfo { public Post() { //Initialization of NOT NULL fields with their default values } [Column(Name = "id", DbType = "int", CanBeNull = false, IsDbGenerated = true, IsPrimaryKey = true)] public int ID { get; set; } private EntitySet<CategoryPost> _categoryRef = new EntitySet<CategoryPost>(); [Association(Name = "tm_rel_categories_posts_fk2", IsForeignKey = true, Storage = "_categoryRef", ThisKey = "ID", OtherKey = "PostID")] public EntitySet<CategoryPost> CategoryRef { get { return _categoryRef; } set { _categoryRef.Assign(value); } } } CategoryPost [Table(Name = "tm_rel_categories_posts")] public class CategoryPost { [Column(Name = "id", DbType = "int", CanBeNull = false, IsDbGenerated = true, IsPrimaryKey = true)] public int ID { get; set; } [Column(Name = "fk_post", DbType = "int", CanBeNull = false)] public int PostID { get; set; } [Column(Name = "fk_category", DbType = "int", CanBeNull = false)] public int CategoryID { get; set; } private EntityRef<Post> _post = new EntityRef<Post>(); [Association(Name = "tm_rel_categories_posts_fk2", IsForeignKey = true, Storage = "_post", ThisKey = "PostID", OtherKey = "ID")] public Post Post { get { return _post.Entity; } set { _post.Entity = value; } } private EntityRef<Category> _category = new EntityRef<Category>(); [Association(Name = "tm_rel_categories_posts_fk", IsForeignKey = true, Storage = "_category", ThisKey = "CategoryID", OtherKey = "ID")] public Category Category { get { return _category.Entity; } set { _category.Entity = value; } } } Category [Table(Name="tm_categories")] public class Category { [Column(Name = "id", DbType = "int", CanBeNull = false, IsDbGenerated = true, IsPrimaryKey = true)] public int ID { get; set; } [Column(Name = "fk_parent", DbType = "int", CanBeNull = true)] public int ParentID { get; set; } private EntityRef<Category> _parent = new EntityRef<Category>(); [Association(Name = "tm_posts_fk2", IsForeignKey = true, Storage = "_parent", ThisKey = "ParentID", OtherKey = "ID")] public Category Parent { get { return _parent.Entity; } set { _parent.Entity = value; } } [Column(Name = "name", DbType = "varchar(100)", CanBeNull = false)] public string Name { get; set; } } So what am I doing wrong? How to make it possible to insert a post that doesn't belong to any category? How to insert categories with no posts?

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  • Searching in an Arraylist

    - by Puchatek
    Currently I have two classes. A Classroom class and a School class. I would like to write a method in the School class public void showClassRoomDetails which would find the classroom details by only using the teacherName. e.g. teacherName = Daniel className = Science teacherName = Bob className = Maths so when I input Bob, it would print out Bob and Maths many, thanks public class Classroom { private String classRoomName; private String teacherName; public void setClassRoomName(String newClassRoomName) { classRoomName = newClassRoomName; } public String returnClassRoomName() { return classRoomName; } public void setTeacherName(String newTeacherName) { teacherName = newTeacherName; } public String returnTeacherName() { return teacherName; } } import java.util.ArrayList; public class School { private ArrayList<Classroom> classrooms; private String classRoomName; private String teacherName; public School() { classrooms = new ArrayList<Classroom>(); } public void addClassRoom(Classroom newClassRoom, String theClassRoomName) { classrooms.add(newClassRoom); classRoomName = theClassRoomName; } public void addTeacherToClassRoom(int classroomId, String TeacherName) { if (classroomId < classrooms.size() ) { classrooms.get(classroomId).setTeacherName(TeacherName); } } public void showClassRoomDetails { //loop System.out.println(returnClassRoomName); System.out.println(returnTeacherName); } }

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  • Wordpress loop not showing 'else' when no posts exist

    - by Reuben
    When no posts exist I'm used to seeing the message after the else, and I'm not sure why it's not showing it now? Code: <?php $args = array( 'post_type' => 'event', 'posts_per_page' => 1, 'post_status' => 'future', 'order' => 'ASC' ); $loop = new WP_Query( $args ); if ( have_posts() ) : while ( $loop->have_posts() ) : $loop->the_post(); ?> <div class="event_preview_title"><?php the_title(); ?></div> <div class="event_details"> <div class="event_date"><?php the_time('m/d/y'); ?></div> <div class="event_time"><?php the_time('g:i A'); ?></div> </div> <?php the_post_thumbnail( array(65,65) ); ?> <a class="clickthrough" href="<?php bloginfo('wpurl'); ?>/events"></a> <?php endwhile; else: ?> <p>Bluebird Books may be coming soon to a neighborhood near you!<br /> We are currently on hiatus planning our next season's schedule. New tour dates will be posted to this page once confirmed. Meanwhile, inquiries about appearances and programs are welcomed! If you are interested in having Bluebird visit your business, school, or special event, please contact us.</p> <?php endif; ?> Thanks!

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  • Django left join m2m field.

    - by duder
    Here's my Model: class User(models.Model): pass class Item(models.Model): pass class ItemVote(models.Model): user = models.ForeignKey(User) item = models.ForeignKey(Item) vote = models.BooleanField() I want to retrieve a list of Items, and I want to know if the current user has voted for each Item. How do I alter my query object so that it will generate sql similar to: SELECT ... FROM items LEFT OUTER JOIN item_votes ON (item_votes.user_id = ? AND item_votes.item_id = items.id)

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  • WxPython multiple grid instances

    - by randomPythonHacker
    Does anybody know how I can get multiple instances of the same grid to display on one frame? Whenever I create more than 1 instance of the same object, the display of the original grid widget completely collapses and I'm left unable to do anything with it. For reference, here's the code: import wx import wx.grid as gridlib class levelGrid(gridlib.Grid): def __init__(self, parent, rows, columns): gridlib.Grid.__init__(self, parent, -1) self.moveTo = None self.CreateGrid(rows, columns) self.SetDefaultColSize(32) self.SetDefaultRowSize(32) self.SetColLabelSize(0) self.SetRowLabelSize(0) self.SetDefaultCellBackgroundColour(wx.BLACK) self.EnableDragGridSize(False) class mainFrame(wx.Frame): def __init__(self, parent, id, title): wx.Frame.__init__(self, parent, id, title, size=(768, 576)) editor = levelGrid(self, 25, 25) panel1 = wx.Panel(editor, -1) #vbox = wx.BoxSizer(wx.VERTICAL) #vbox.Add(editor, 1, wx.EXPAND | wx.ALL, 5) #selector = levelGrid(self, 1, 25) #vbox.Add(selector, 1, wx.EXPAND |wx.BOTTOM, 5) self.Centre() self.Show(True) app = wx.App() mainFrame(None, -1, "SLAE") app.MainLoop()

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  • Java DAO caching

    - by santiagobasulto
    I'm developing a medium Java app, and i'm facing a small problem due to my lack of experience. I've a custom DAO, which gets "Article" objects from the Database. I've the Article class, and the DAO has a method called getArticle(int id), this method returns an Article. The Article has a Category object, and I'm using lazy loading. So, when I request for an article's category (Article a = new Article(); a.getCategory();) the Article class gets the Category from the DAO and then returns it. I'm now thinking to cache it, so when I request multiple times to an article's category, the database is only queried one time. My question is: where should I put that cache? I can put it on the Article class (in the DTO), or I can put it on the DAO class. What do you say?

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  • functional dependencies vs type families

    - by mhwombat
    I'm developing a framework for running experiments with artificial life, and I'm trying to use type families instead of functional dependencies. Type families seems to be the preferred approach among Haskellers, but I've run into a situation where functional dependencies seem like a better fit. Am I missing a trick? Here's the design using type families. (This code compiles OK.) {-# LANGUAGE TypeFamilies, FlexibleContexts #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u => a -> StateT u IO a -- plus other functions class Universe u where type MyAgent u :: * withAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } defaultWithAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () defaultWithAgent = undefined -- stub -- plus default implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- .. and they'll also need to make SimpleUniverse an instance of Universe -- for their agent type. -- instance Universe SimpleUniverse where type MyAgent SimpleUniverse = Bug withAgent = defaultWithAgent -- boilerplate -- plus similar boilerplate for other functions Is there a way to avoid forcing my users to write those last two lines of boilerplate? Compare with the version using fundeps, below, which seems to make things simpler for my users. (The use of UndecideableInstances may be a red flag.) (This code also compiles OK.) {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u a => a -> StateT u IO a -- plus other functions class Universe u a | u -> a where withAgent :: Agent a => (a -> StateT u IO a) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } instance Universe SimpleUniverse a where withAgent = undefined -- stub -- plus implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- And now my users only have to write stuff like... -- u :: SimpleUniverse u = SimpleUniverse "mydir"

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  • Doubt in abstract classes

    - by mohit
    public abstract class Person { private String name; public Person(String name) { this.name = name; System.out.println("Person"); } public String getName() { return name; } abstract public String getDescription(); } public class Student extends Person { private String major; public Student(String name, String major) { super(name); this.major = major; } public String getMajor() { return major; } @Override public String getDescription() { return "student" + super.getName() + " having" + major; } } public class PersonTest { public static void main(String[] args) { Person person = new Student("XYZ", "ABC"); System.out.println(person.getDescription()); } } Ques: We cannot create objects of abstract classes, then why Person Constructor has been invoked, even its an abstract class?

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  • center text in div

    - by Son of anarchy
    <div> <div class="left"> <div align="center" class="node"> <div class="nodeText"> <h2 >test</h2> </div> <div class="node"> <h2>test</h2> </div> <div class="node"> <h2>test</h2> </div> <div> I need to center text in div nothing seems to work .left { float:left; width:200px; border:solid 1px black; text-align: center; } .node { height:200px; border:solid 1px black; margin:0 auto; } .nodeText{ vertical-align: middle; } h2{ text-align: center; } Tnxs

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  • Help with listView in Android

    - by jul
    Hi, I'm just starting with Android and can't find how to display a list in my activity. I get some restaurant data from a web service and I'd like to show the results in a list. The activity, the restaurant class and the layout main.xml are shown below. How can I display, for instance, the list of the restaurant names in the ListView 'list' of my layout? thank you Jul public class Atable extends ListActivity { RestaurantList restaurantList; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //Here I set restaurantList //Now how can I display, for example, the list of the names of the restaurants } main.xml <LinearLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/search" /> <EditText android:id="@+id/search" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1"/> </LinearLayout> <LinearLayout android:orientation="vertical" android:layout_width="wrap_content" android:layout_height="wrap_content"> <ListView android:id="@+id/android:list" android:layout_width="wrap_content" android:layout_height="wrap_content"/> <TextView android:id="@+id/android:empty" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/noresults"/> </LinearLayout> </LinearLayout> Restaurant list class package org.digitalfarm.atable; import java.util.List; public class RestaurantList { private List<Restaurant> restaurants; public List<Restaurant> getRestaurants() { return restaurants; } public void setRestaurants(List<Restaurant> restaurants) { this.restaurants = restaurants; } } Restaurant class package org.digitalfarm.atable; public class Restaurant { private String name; private float latitude; private float longitude; public String getName() { return name; } public void setName(String name) { this.name = name; } public float getLatitude() { return latitude; } public void setLatitude(float latitude) { this.latitude = latitude; } public float getLongitude() { return longitude; } public void setLongitude(float longitude) { this.longitude = longitude; } }

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  • Questions about use lib for perl

    - by Tyug
    I use use lib "./DIR" to grab a library from a folder elsewhere. However, it doesn't seem to work on my server, but it works fine on my local desktop. Any particular reasons? And one more question, does use lib get propagated within several modules? Two situations: Say I make a base class that requires a few libraries, but I know that it needs to be extended and the extended class will need to use another library. Can I put the use lib command in the base class? or will I need to put it in every extending class? Finally, can I just have a use package where package contains a bunch of use lib, will it propagate the use lib statements over to my current module? <-- I don't think so, but asking anyways Thanks in advance! Tyug

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  • jQuery each function, getting the data out of it

    - by Ankur
    I am trying to use the jQuery each function (line 5) to display the results of an AJAX call. when I write resultObj.value on line 6 how come I am not getting any data? Am I making a syntax error (I am pretty sure that I must be)? success : function(resultObj) { count = count+1; $(".objHolder").filter("#"+id).append("<table border='1' cellspacing='4' cellpadding='4' class='preTable' id='"+id+"' level='"+count+"'><tr><td class='preItem' id='"+id+"' level='"+count+"'><img src='images/right.jpg' width='16' height='10' /></td><td class='preList'>&nbsp;</td><td class='preHolder' level='"+count+"'>&nbsp;</td></tr></table>"); isClicked[level]="yes"; $.each(resultObj, function(index, value){ $(".preHolder").filter("#"+id).append(resultObj.value); }); } });

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  • How can I use BeanUtils copyProperties to copy from boolean to Boolean?

    - by carrier
    BeanUtils copyProperties, out of the box, doesn't seem to handle copying from Boolean object properties to boolean primitive properties. I figured I could create and register a converter to handle this, but that just didn't seem to work. So, how can I use BeanUtils to copy the properties from class Source to class Destination where: public class Destination { private boolean property; public boolean isProperty() { return property; } public void setProperty(boolean property) { this.property = property; } } public class Source{ private Boolean property; public Boolean getProperty() { return property; } public void setProperty(Boolean property) { this.property = property; } }

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  • Overloading generic implicit conversions

    - by raichoo
    Hi I'm having a little scala (version 2.8.0RC1) problem with implicit conversions. Whenever importing more than one implicit conversion the first one gets shadowed. Here is the code where the problem shows up: // containers class Maybe[T] case class Nothing[T]() extends Maybe[T] case class Just[T](value: T) extends Maybe[T] case class Value[T](value: T) trait Monad[C[_]] { def >>=[A, B](a: C[A], f: A => C[B]): C[B] def pure[A](a: A): C[A] } // implicit converter trait Extender[C[_]] { class Wrapper[A](c: C[A]) { def >>=[B](f: A => C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, f) } def >>[B](b: C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, { (x: A) => b } ) } } implicit def extendToMonad[A](c: C[A]) = new Wrapper[A](c) } // instance maybe object maybemonad extends Extender[Maybe] { implicit object MaybeMonad extends Monad[Maybe] { override def >>=[A, B](a: Maybe[A], f: A => Maybe[B]): Maybe[B] = { a match { case Just(x) => f(x) case Nothing() => Nothing() } } override def pure[A](a: A): Maybe[A] = Just(a) } } // instance value object identitymonad extends Extender[Value] { implicit object IdentityMonad extends Monad[Value] { override def >>=[A, B](a: Value[A], f: A => Value[B]): Value[B] = { a match { case Value(x) => f(x) } } override def pure[A](a: A): Value[A] = Value(a) } } import maybemonad._ //import identitymonad._ object Main { def main(args: Array[String]): Unit = { println(Just(1) >>= { (x: Int) => MaybeMonad.pure(x) }) } } When uncommenting the second import statement everything goes wrong since the first "extendToMonad" is shadowed. However, this one works: object Main { implicit def foo(a: Int) = new { def foobar(): Unit = { println("Foobar") } } implicit def foo(a: String) = new { def foobar(): Unit = { println(a) } } def main(args: Array[String]): Unit = { 1 foobar() "bla" foobar() } } So, where is the catch? What am I missing? Regards, raichoo

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  • Providing custom database functionality to custom asp.net membership provider

    - by IrfanRaza
    Hello friends, I am creating custom membership provider for my asp.net application. I have also created a separate class "DBConnect" that provides database functionality such as Executing SQL statement, Executing SPs, Executing SPs or Query and returning SqlDataReader and so on... I have created instance of DBConnect class within Session_Start of Global.asax and stored to a session. Later using a static class I am providing the database functionality throughout the application using the same single session. In short I am providing a single point for all database operations from any asp.net page. I know that i can write my own code to connect/disconnect database and execute SPs within from the methods i need to override. Please look at the code below - public class SGI_MembershipProvider : MembershipProvider { ...... public override bool ChangePassword(string username, string oldPassword, string newPassword) { if (!ValidateUser(username, oldPassword)) return false; ValidatePasswordEventArgs args = new ValidatePasswordEventArgs(username, newPassword, true); OnValidatingPassword(args); if (args.Cancel) { if (args.FailureInformation != null) { throw args.FailureInformation; } else { throw new Exception("Change password canceled due to new password validation failure."); } } ..... //Database connectivity and code execution to change password. } .... } MY PROBLEM - Now what i need is to execute the database part within all these overriden methods from the same database point as described on the top. That is i have to pass the instance of DBConnect existing in the session to this class, so that i can access the methods. Could anyone provide solution on this. There might be some better techniques i am not aware of that. The approach i am using might be wrong. Your suggessions are always welcome. Thanks for sharing your valuable time.

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  • java: "downcasting" to new object / opposite of slicing

    - by rhavin
    Sorry, i really dont know how to make a headline for that question; maybe there is a name for what im trying to do that i dont know, but i can explain it with some code: Guess you have a class that unfortunately neither has a copy-constructor nor a public static copy method. class A { private int i; // <- private, cant access String x; // <- even worse: cant access unless in same pkg! /* … other stuff, ctor, etc. … */ public A clone() { A a = new A(); a.i = i; a.x = x; return x; } } Guess further, there is some function that returns an object of that class: public static A someFn(x,y,z); Now the problem: I want to derive from that class to add some functionality. Unfortunately, i neither have a sizeof in java nor a cc or static copy method. So when i do a class B extends A { protected w; public B clone() { /* as usual */ } } then i can clone my B and get a new one, but how can i convert the returned A from someFn() into a B. Is there anyway to do the opposite of slicing in java? if i clone it, it's still an A, and i cant copy it field by field. This is all simple in c++, but how to do this in Java?

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  • NUnit doesn't work well with Assert.AreEqual

    - by stasal
    Hi! I'm new to unit-testing and NUit in particular. I'm just typing some examples from the book which refers to Java and JUnit. But I'm using C# instead. The problem is: I've got a class with overriden methods such as Equals() and GetHashCode(), but when I am trying to compare two objects of this class with Assert.AreEqual() my code is not called, so I get an exception. Assert.True(MyClass.Equals(MyClass2)) does work well. But I don't wanna use this construction instead of Assert.AreEqual(). Where the problem can be? Here is the class: public class Money { public int amount; protected string currency; public Money(int amount, string currency) { this.amount = amount; this.currency = currency; } public new bool Equals(object obj) { if (obj == null) return false; Money money = (Money)obj; return (amount == money.amount) && (Currency().Equals(money.Currency())); } public new int GetHashCode() { return (string.Format("{0}{1}", amount, currency)).GetHashCode(); } public static Money Dollar(int amount) { return new Money(amount, "USD"); } public static Money Franc(int amount) { return new Money(amount, "CHF"); } public Money Times(int multiplier) { return new Money(amount * multiplier, currency); } public string Currency() { return currency; } } And the test method itself: [TestFixture] public class DollarTest { [Test] public void TestMultiplication() { Money five = Money.Dollar(5); Assert.True(Money.Dollar(10).Equals(five.Times(2))); // ok Assert.AreEqual(Money.Dollar(10), five.Times(2)); // fails } } Thanks.

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  • prototype findElements querySelectorAll error

    - by JD
    i'm call the "down" function but am getting an invalid argument using 1.6.1_rc2 here's the html snippet: <TR id=000000214A class="activeRow searchResultsDisplayOver" conceptID="0000001KIU"> <TD> <DIV class=gridRowWrapper> <SPAN class=SynDesc>Asymmetric breasts</SPAN> <DIV class=buttonWrapper> <SPAN class=btnAddFav title="Add to Favorites">&nbsp;</SPAN> </DIV> </DIV> </TD> </TR> here's the code: var description = row.down('span.SynDesc').innerHTML; row is a dom reference to the element. prototype is appending a # then the id of the element: findElements: function(root) { root = root || document; var e = this.expression, results; switch (this.mode) { case 'selectorsAPI': if (root !== document) { var oldId = root.id, id = $(root).identify(); id = id.replace(/[\.:]/g, "\\$0"); e = "#" + id + " " + e; } results = $A(root.querySelectorAll(e)).map(Element.extend); <-- e = "#000000214A span.SynDesc" root.id = oldId; return results; case 'xpath': return document._getElementsByXPath(this.xpath, root); default: return this.matcher(root); } i get an "invalid argument" error? if i put a breakpoint before the offending line and change e to be equal to "span.SynDesc" it works fine. help. :)

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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • How to handle failure to release a resource which is contained in a smart pointer?

    - by cj
    How should an error during resource deallocation be handled, when the object representing the resource is contained in a shared pointer? Smart pointers are a useful tool to manage resources safely. Examples of such resources are memory, disk files, database connections, or network connections. // open a connection to the local HTTP port boost::shared_ptr<Socket> socket = Socket::connect("localhost:80"); In a typical scenario, the class encapsulating the resource should be noncopyable and polymorphic. A good way to support this is to provide a factory method returning a shared pointer, and declare all constructors non-public. The shared pointers can now be copied from and assigned to freely. The object is automatically destroyed when no reference to it remains, and the destructor then releases the resource. /** A TCP/IP connection. */ class Socket { public: static boost::shared_ptr<Socket> connect(const std::string& address); virtual ~Socket(); protected: Socket(const std::string& address); private: // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; But there is a problem with this approach. The destructor must not throw, so a failure to release the resource will remain undetected. A common way out of this problem is to add a public method to release the resource. class Socket { public: virtual void close(); // may throw // ... }; Unfortunately, this approach introduces another problem: Our objects may now contain resources which have already been released. This complicates the implementation of the resource class. Even worse, it makes it possible for clients of the class to use it incorrectly. The following example may seem far-fetched, but it is a common pitfall in multi-threaded code. socket->close(); // ... size_t nread = socket->read(&buffer[0], buffer.size()); // wrong use! Either we ensure that the resource is not released before the object is destroyed, thereby losing any way to deal with a failed resource deallocation. Or we provide a way to release the resource explicitly during the object's lifetime, thereby making it possible to use the resource class incorrectly. There is a way out of this dilemma. But the solution involves using a modified shared pointer class. These modifications are likely to be controversial. Typical shared pointer implementations, such as boost::shared_ptr, require that no exception be thrown when their object's destructor is called. Generally, no destructor should ever throw, so this is a reasonable requirement. These implementations also allow a custom deleter function to be specified, which is called in lieu of the destructor when no reference to the object remains. The no-throw requirement is extended to this custom deleter function. The rationale for this requirement is clear: The shared pointer's destructor must not throw. If the deleter function does not throw, nor will the shared pointer's destructor. However, the same holds for other member functions of the shared pointer which lead to resource deallocation, e.g. reset(): If resource deallocation fails, no exception can be thrown. The solution proposed here is to allow custom deleter functions to throw. This means that the modified shared pointer's destructor must catch exceptions thrown by the deleter function. On the other hand, member functions other than the destructor, e.g. reset(), shall not catch exceptions of the deleter function (and their implementation becomes somewhat more complicated). Here is the original example, using a throwing deleter function: /** A TCP/IP connection. */ class Socket { public: static SharedPtr<Socket> connect(const std::string& address); protected: Socket(const std::string& address); virtual Socket() { } private: struct Deleter; // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; struct Socket::Deleter { void operator()(Socket* socket) { // Close the connection. If an error occurs, delete the socket // and throw an exception. delete socket; } }; SharedPtr<Socket> Socket::connect(const std::string& address) { return SharedPtr<Socket>(new Socket(address), Deleter()); } We can now use reset() to free the resource explicitly. If there is still a reference to the resource in another thread or another part of the program, calling reset() will only decrement the reference count. If this is the last reference to the resource, the resource is released. If resource deallocation fails, an exception is thrown. SharedPtr<Socket> socket = Socket::connect("localhost:80"); // ... socket.reset();

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