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• C++ memory management of reference types

  - by Russel

  Hello, I'm still a fairly novice programmer and I have a question about c++ memory management with refence types. First of all, my understanding of reference types: A pointer is put on the stack and the actual data that the pointer points to is created and placed on the heap. Standard arrays and user defined classes are refence types. Is this correct? Second, my main question is do c and c++'s memory management mechanisms (malloc, free and new, delete) always handle this properly and free the memory that a class or array is pointing to? Does everything still work if those pointers get reassigned somehow to other objects of the same size/type on the heap? What if a class has a pointer member that points to another object? I am assuming that delete/freeing the class object doesn't free what it's member pointer points to, is that correct? Thanks all! -R

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• SQL returns non-array value in PHP

  - by DeadMG

  $request = 'SELECT * FROM flight WHERE Id = \''.$_SESSION['LFLightRadio'].'\''; $data = mysql_fetch_array(mysql_query($request, $SQL)); echo '<table class="table">'; foreach($data as $key => $value) { echo '<th class="head" align="center" height="19">'.$key.'</th>'; } echo '<tr>'; foreach($data as $key => $value) { echo '<td class="cell" align="center" height="19">'.$value.'</td>'; } echo '</tr></table>'; I know that the LFlightRadio value is set, and is a value returned by the Id value of a previously returned row from the flight database. So within "flight", a record definitely exists with this Id. But, this still gives me a non-array result, so that when I try to use foreach on it, it errors out. Suggestions?

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• How do i get file path of my file in java enterprise application?

  - by Nitesh Panchal

  Hello, I created java enterprise application and it consists of ejb module and web application. I have plain old xml file in source packages folder in package "common" in my ejb module. I want to pass this file path in File() constructor for one class in ejb module. How do i do it? If i pass any of the below it doesn't work :- new File("abc.xml"); //this take file from glassfish/domains/domain1 :( new File("./abc.xml"); I don't want to pass hardcode path like /home/administrator/appname/module/etc.. I want the path relative from my ejb module. Please help me. I've tried all things. Actually when i created a class in same folder and then try classname.getResource("abc.xml").getPath() it works fine. But what if i don't have any class in that folder. Waiting for your replies

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• Use SQL query to populate property in nHibernate mapping file

  - by brainimus

  I have an object which contains a property that is the result of an SQL statement. How do I add the SQL statement to my nHibernate mapping file? Example Object: public class Library{ public int BookCount { get; set; } } Example Mapping File: <hibernate-mapping> <class name="Library" table="Libraries"> <property name="BookCount" type="int"> <- This is where I want the SQL query to populate the value. -> </class> </hibernate-mapping> Example SQL Query: SELECT COUNT(*) FROM BOOKS WHERE BOOKS.LIBRARY_ID = LIBRARIES.ID

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• Best way to map/join two autogenerated enums

  - by tomlip

  What is the best C++ (not C++11) way of joining two enums from autogenerated class similar to one presented below: namespace A { namespace B { ... class CarInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } class BikeInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } } } What is needed is unified enum State for both classes that is seen to outside world alongside with safe type conversion. The best and probably most straightforward way I came up with is to create external enum: enum State { Running, Stopped, Broken } together with conversion functions State stateEnumConv(A::B::CarInfo::State aState); State stateEnumConv(A::B::BikeInfo::State aState); A::B::CarInfo::State stateEnumConv(State aState); A::B::BikeInfo::State stateEnumConv(State aState); Direction into right approach is needed. Gosh coming from C I hate those long namespaces everywhere an I wish it could be only A::B level like in presented example. Four conversion functions seem redundant note that CarInfo::State and BikeInfo::State has same enum "members".

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• What Can A 'TreeDict' (Or Treemap) Be Used For In Practice?

  - by Seun Osewa

  I'm developing a 'TreeDict' class in Python. This is a basically a dict that allows you to retrieve its key-value pairs in sorted order, just like the Treemap collection class in Java. I've implemented some functionality based on the way unique indexes in relational databases can be used, e.g. functions to let you retrieve values corresponding to a range of keys, keys greater than, less than or equal to a particular value in sorted order, strings or tuples that have a specific prefix in sorted order, etc. Unfortunately, I can't think of any real life problem that will require a class like this. I suspect that the reason we don't have sorted dicts in Python is that in practice they aren't required often enough to be worth it, but I want to be proved wrong. Can you think of any specific applications of a 'TreeDict'? Any real life problem that would be best solved by this data structure? I just want to know for sure whether this is worth it.

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• Question about C# properties

  - by Impz0r

  Hey there, i bumped the other day into a little problem regarding C#'s properties. Let's say i do have this setup: public class Point { public float X; public float Y; } public class Control { protected Point m_Position = new Point(); public Position { get { return m_Position; } set { m_Position = value; } // reorganize internal structure.. reorganize(); } protected reorganize() { // do some stuff } } This is all fine, but when it comes to usage, i could write something like: Control myControl = new Control(); myControl.Position.X = 1.0f; The thing is, my Control class wont recognize that the Position has been changed because set hasn't been called. So i guess my question is, is there a way to make Control aware of any Position changes? Thanks in advance! Mfg Imp

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• Problem overridding virtual function

  - by William

  Okay, I'm writing a game that has a vector of a pairent class (enemy) that s going to be filled with children classes (goomba, koopa, boss1) and I need to make it so when I call update it calls the childclasses respective update. I have managed to create a example of my problem. #include <stdio.h> class A{ public: virtual void print(){printf("Hello from A");} }; class B : public A{ public: void print(){printf("Hello from B");} }; int main(){ A ab = B(); ab.print(); while(true){} } Output wanted: "Hello from B" Output got: "Hello from A" How do I get it to call B's print function?

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• Collectable<T> serialization, Root Namespaces on T in .xml files.

  - by Stacey

  I have a Repository Class with the following method... public T Single<T>(Predicate<T> expression) { using (var list = (Models.Collectable<T>)System.Xml.Serializer.Deserialize(typeof(Models.Collectable<T>), FileName)) { return list.Find(expression); } } Where Collectable is defined.. [Serializable] public class Collectable<T> : List<T>, IDisposable { public Collectable() { } public void Dispose() { } } And an Item that uses it is defined.. [Serializable] [System.Xml.Serialization.XmlRoot("Titles")] public partial class Titles : Collectable<Title> { } The problem is when I call the method, it expects "Collectable" to be the XmlRoot, but the XmlRoot is "Titles" (all of object Title). I have several classes that are collected in .xml files like this, but it seems pointless to rewrite the basic methods for loading each up when the generic accessors do it - but how can I enforce the proper root name for each file without hard coding methods for each one? The [System.Xml.Serialization.XmlRoot] seems to be ignored.

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• Reuse C++ Header files

  - by Amrish

  Guys, I have a Visual C++ solution with 2 projects AlgorithmA & AlgorithmB and both share a common header file RunAlgo.h with the class declaration. Each project in the solution has its own unique implementation for the header file. I am trying to compile a DLL out of the common header file RunAlgo.h and add reference to this DLL in the projects AlgorithmA & AlgorithmB. I have then included separate RunAlgo.cpp definition file in both my projects. The problem is that I am getting linker errors while compiling the new DLL project which has only the header file. So, the question is Can a header file with only class declaration be compiled into a DLL (Similar to class library containing an Interface in C#)? For the above scenario, is there a better approach to reuse the common Header file among projects? Should the above method work (re-check my code?)

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• test cases for testing a strtok-alike function [C++]

  - by Neeraj

  Consider the following class definition: class StrToTokens { StrToTokens(const char* str, const char* delimiters = "\t\r\n"); //constructor string getNextToken(); void reset(); bool empty(); } Can someone list some good testcases to test the above class. A few I could think of are: empty string, empty delimiters, repeated delimiters, consecutive delimiters, string with only delimiters. However, the interviewer expected some more(better ones). Can you help out. Thanks.

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• django form creation on init

  - by John

  Hi, How can I add a field in the form init function? e.g. in the code below I want to add a profile field. class StaffForm(forms.ModelForm): def __init__(self, user, *args, **kwargs): if user.pk == 1: self.fields['profile'] = forms.CharField(max_length=200) super(StaffForm, self).__init__(*args, **kwargs) class Meta: model = Staff I know I can add it just below the class StaffForm.... line but I want this to be dynamic depending on what user is passed in so can't do it this way. Thanks

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• Dynamically load a type from an external assembly

  - by Water Cooler v2

  From managed code, how do I load a managed type from another assembly at runtime, assuming the calling code does not have a static reference to the assembly? To clarify, let's say I have class Lib in Lib.cs compiled into Lib.dll. I want to write a class Foo in a separate assembly called Foo.dll, that does not have a reference to Lib.dll statically, but instead loads Lib.dll and then reflects on for the presence of the class Lib and then calls a method on it. Sorry for such an obvious question on Reflection. I figure it'll take much lesser time to get the answer on a forum that to read a few articles.

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• Optional parameters for interfaces

  - by bryanjonker

  Using c# 4.0 -- building an interface and a class that implements the interface. I want to declare an optional parameter in the interface and have it be reflected in the class. So, I have the following: public interface IFoo { void Bar(int i, int j=0); } public class Foo { void Bar(int i, int j=0) { // do stuff } } This compiles, but it doesn't look right. The interface needs to have the optional parameters, because otherwise it doesn't reflect correctly in the interface method signature. Should I skip the optional parameter and just use a nullable type? Or will this work as intended with no side effects or consequences?

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• Can I write functors using a private nested struct?

  - by Kristo

  Given this class: class C { private: struct Foo { int key1, key2, value; }; std::vector<Foo> fooList; }; The idea here is that fooList can be indexed by either key1 or key2 of the Foo struct. I'm trying to write functors to pass to std::find so I can look up items in fooList by each key. But I can't get them to compile because Foo is private within the class (it's not part of C's interface). Is there a way to do this without exposing Foo to the rest of the world? (note: I've got to run to a meeting. I'll be able to post more sample code in about a half hour.)

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• Breakpoint pointing out "objc_autoreleaseNoPool"

  - by Andrew

  So I'm debugging an app in preperation for its app so release, and I enabled a universal breakpoint for "All Exceptions". Since then, everytime I run the app, the console prints: Catchpoint 2 (throw)Pending breakpoint 1 - "objc_exception_throw" resolved objc[11765]: Object 0x8f18ff0 of class __NSCFLocale autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug objc[11765]: Object 0x8f190a0 of class __NSCFNumber autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug objc[11765]: Object 0x8f1fef0 of class __NSCFLocale autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug Literally printed 3 times. I have no idea what this means but it looks bad. Any advice would be appreciated.

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• How to Add Horizontal line in Javascript

  - by user54197

  I would like to add a horizontal seperating line on a dynamic populated table. How do I do this? Below is a snippet. function addNewRow() { $('#displayTable tr:last').after('<tr><td style="font-size:smaller;" class="dataField1"></td><td style="font-size:smaller;" class="dataField2"></td><td style="font-size:smaller;" class="dataField3"></td></tr>'); var $tr = $('#displayTable tr:last'); $tr.find('.dataField1').text($('#txtName').val()); $tr.find('.dataField2').text($('#txtAddress').val()); $tr.find('.dataField3').text('document.write("<tr><td colspan=\"2\"><hr \/><\/td><\/tr>"); }

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• How do I dynamically add and remove line items from an ASP.NET MVC view?

  - by Mike Roosa

  I have a PurchaseOrder model: public class PurchaseOrder { public string OrderNumber { get; set; } public string Customer { get; set; } public IList<LineItem> Lines { get; set; } } and a LineItem class: public class LineItem { public string PartNumber { get; set; } public int Quantity { get; set; } } What I want to do is on my view for the PurhcaseOrder Create action, I need a section for line items. The user should be able to add a new line, remove a line, then submit. One caveat is the PartNumber needs to be a dropdown list of valid parts. What can I do to accomplish what I'm looking for?

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• Segfault when calling a method c++

  - by shuttle87

  I am fairly new to c++ and I am a bit stumped by this problem. I am trying to assign a variable from a call to a method in another class but it always segfaults. My code compiles with no warnings and I have checked that all variables are correct in gdb but the function call itself seems to cause a segfault. The code I am using is roughly like the following: class History{ public: bool test_history(); }; bool History::test_history(){ std::cout<<"test"; //this line never gets executed //more code goes in here return true; } class Game{ private: bool some_function(); public: History game_actions_history; bool local_variable; }; bool Game::some_function(){ local_variable = game_actions_history.test_history(); if (local_variable == true){ return true; } else{ return false; } } Any tips or advice is greatly appreciated!

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• Using a backwards relation (i.e FOO_set) for ModelChoiceField in Django

  - by Bwmat

  I have a model called Movie, which has a ManyToManyField called director to a model called Person, and I'm trying to create a form with ModelChoiceField like so: class MovieSearchForm(forms.Form): producer = forms.ModelChoiceField(label='Produced by', queryset=movies.models.Person.producer_set, required=False) but this seems to be failing to compile (I'm getting a ViewDoesNotExist exception for the view that uses the form, but it goes away if I just replace the queryset with all the person objects), I'm guessing because '.producer_set' is being evaluated too 'early'. How can I get this work? here are the relevant parts of the movie/person classes: class Person(models.Model): name = models.CharField(max_length=100) class Movie(models.Model): ... producer = models.ForeignKey(Person, related_name="producers") director = models.ForeignKey(Person, related_name="directors") What I'm trying to do is get ever Person who is used in the producer field of some Movie.

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• Explanation of output

  - by Anon

  My program class Building { Building() { System.out.print("b "); } Building(String name) { this(); System.out.print("bn " + name); } }; public class House extends Building { House() { System.out.print("h "); // this is line# 1 } House(String name) { this(); // This is line#2 System.out.print("hn " + name); } public static void main(String[] args) { new House("x "); } } We know that compiler will write a call to super() as the first line in the child class's constructor. Therefore should not the output be: b (call from compiler written call to super(), before line#2 b (again from compiler written call to super(),before line#1 ) h hn x But the output is b h hn x Why is that?

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• Code First entity framework connection string

  - by Suneel Dixit

  I have 3 class projects in my solutions. 1. MVC4 project 2. Domain 3. Tests In the MVC4 project I have added a web.config file with the connection string as <add name="EfDbContext" connectionString="Data Source=.;Initial Catalog=SportsStore;Integrated Security=true;" providerName="System.Data.SqlClient"/> I have a class by name EfDbContext in Domain project which inherits DbContext. When I view the website in browser, I get the server not found error. I debugged the EfDbContext class and found that the Database.Connection.ConnectionString is set to \SqlExpress with database as EfDbContext. Why is that?

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• bulk update/delete entities of different kind in db.run_in_transaction

  - by Ray Yun

  Here goes pseudo code of bulk update/delete entities of different kind in single transaction. Note that Album and Song entities have AlbumGroup as root entity. class AlbumGroup: pass class Album: group = db.ReferenceProperty(reference_class=AlbumGroup,collection_name="albums") class Song: album = db.ReferenceProperty(reference_class=Album,collection_name="songs") def bulk_update_album_group(album_group): updated = [album_group] deleted = [] for album in album_group.albums: updated.append(album) for song in album.songs: if song.is_updated: updated.append(song) if song.is_deleted: deleted.append(song) db.put(updated) db.delete(deleted) a = AlbumGroup.all().filter("...").get() # bulk update/delete album group. for simplicity, album cannot be deleted. db.run_in_transaction(bulk_update_album_group,a) But I met a famous "Only Ancestor Queries in Transactions" error at the iterating reference properties like album.songs or album_group.albums. I guess ancestor() filter does not help because those entities are modified in memory. Should I not to iterate reference property in transaction function and always provide them as function parameters like def bulk_update_album_group(updated,deleted): ??? Is there any good coding pattern for this situation?

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• Reading file data during form's clean method

  - by Dominic Rodger

  So, I'm working on implementing the answer to my previous question. Here's my model: class Talk(models.Model): title = models.CharField(max_length=200) mp3 = models.FileField(upload_to = u'talks/', max_length=200) Here's my form: class TalkForm(forms.ModelForm): def clean(self): super(TalkForm, self).clean() cleaned_data = self.cleaned_data if u'mp3' in self.files: from mutagen.mp3 import MP3 if hasattr(self.files['mp3'], 'temporary_file_path'): audio = MP3(self.files['mp3'].temporary_file_path()) else: # What goes here? audio = None # setting to None for now ... return cleaned_data class Meta: model = Talk Mutagen needs file-like objects - the first case (where the uploaded file is larger than the size of file handled in memory) works fine, but I don't know how to handle InMemoryUploadedFile that I get otherwise. I've tried: # TypeError (coercing to Unicode: need string or buffer, InMemoryUploadedFile found) audio = MP3(self.files['mp3']) # TypeError (coercing to Unicode: need string or buffer, cStringIO.StringO found) audio = MP3(self.files['mp3'].file) # Hangs seemingly indefinitely audio = MP3(self.files['mp3'].file.read()) Is there something wrong with mutagen, or am I doing it wrong?

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• RotationAsync with each row in List view

  - by Labeeb P

  Hi, From this answer in stack overflow and the sample project referred there, i got the Idea of RotationAsync, where a progress bar work fine with device rotation. But my problem is, i have a listview with each row there is progress bar. And is there any way to retain the progress while rotation for reach row. Me creating onclicklistener object for the button click listener in getview function of my adapter class. Where its onClick function call the AsyncTask class Since each getview (row) is calling different instant of my AsyncTask, i cannot make it static of single ton class. Any Idea on this. Thanks.

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