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  • What is the ambiguity in this piece of code?

    - by cambr
    #include <iostream> using namespace std; class A { public: void eat(){ cout<<"A";} }; class B: public A { public: void eat(){ cout<<"B";} }; class C: public A { public: void eat(){ cout<<"C";} }; class D: public B,C { public: void eat(){ cout<<"D";} }; int main(){ A *a = new D(); a->eat(); } I am not sure this is called diamond problem or not, but why doesn't this work? When I said, a->eat() (remember eat() is not virtual), there is only one possible eat() to call, that of A. Why then, do I get this error: 'A' is an ambiguous base of 'D'

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  • Python - Get Instance Variables

    - by Chris Bunch
    Is there a built-in method in Python to get an array of all a class' instance variables? For example, if I have this code: class hi: def __init__(self): self.ii = "foo" self.kk = "bar" Is there a way for me to do this: >>> mystery_method(hi) ["ii", "kk"] Thanks guys! Edit: I originally had asked for class variables erroneously. Thanks to all who brought this to my attention!

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  • How do I flag only one of the formsets in django admin?

    - by azuer88
    I have these (simplified) models: class Question(models.Model): question = models.CharField(max_length=60) class Choices(models.Model): question = models.ForeignKey(Question) text = models.CharField(max_length=60) is_correct = models.BooleanField(default=False) I've made Choices as an inline of Question (in admin). Is there a way to make sure that only one Choice will have is_correct = True? Ideally, is_correct will be displayed as a radio button when it is displayed in the admin formset (TabularInline). my admin.py has: from django.contrib import admin class OptionInline(admin.TabularInline): model = Option extra = 5 max_num = 5 class QuestionAdmin(admin.ModelAdmin): inlines = [OptionInline, ] admin.site.register(QType) admin.site.register(Question, QuestionAdmin)

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  • Passing Activity to non-activity object properly

    - by rayman
    In my app ive got a non-activity object which it's role is being a manager class. many times i need to pass "source activity" to methods as parameter to that manager class in order to make some operations on that activity. for exaple let's assume we have MyActivity which gotta do some toast. so i have this manager class called MyManager, and i have this method in it raiseToast(Activity sourceActivity) { Toast.makeText(sourceActivity, demo, Toast.LENGTH_LONG).show(); } and from Myactivity class we calling that method this way: MyManager manager=new MyManager(); manager.raitetoast(MyActivity.this); it works fine. what I'm asking here, is this a proper way to pass an Activity as parameter to a non-activity object? I'm having a memory leaks on real device(not the emulator), I wonder if this could also causing any reason for that? Thanks Idan.

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  • When to use "property" builtin: auxiliary functions and generators

    - by Seth Johnson
    I recently discovered Python's property built-in, which disguises class method getters and setters as a class's property. I'm now being tempted to use it in ways that I'm pretty sure are inappropriate. Using the property keyword is clearly the right thing to do if class A has a property _x whose allowable values you want to restrict; i.e., it would replace the getX() and setX() construction one might write in C++. But where else is it appropriate to make a function a property? For example, if you have class Vertex(object): def __init__(self): self.x = 0.0 self.y = 1.0 class Polygon(object): def __init__(self, list_of_vertices): self.vertices = list_of_vertices def get_vertex_positions(self): return zip( *( (v.x,v.y) for v in self.vertices ) ) is it appropriate to add vertex_positions = property( get_vertex_positions ) ? Is it ever ok to make a generator look like a property? Imagine if a change in our code meant that we no longer stored Polygon.vertices the same way. Would it then be ok to add this to Polygon? @property def vertices(self): for v in self._new_v_thing: yield v.calculate_equivalent_vertex()

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  • java connectivity with mysql error

    - by abson
    I just started with the connectivity and tried this example. I have installed the necessary softwares. Also copied the jar file into the /ext folder.Yet the code below has the following error import java.sql.*; public class Jdbc00 { public static void main(String args[]){ try { Statement stmt; Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/mysql" DriverManager.getConnection(url,"root", "root"); //Display URL and connection information System.out.println("URL: " + url); System.out.println("Connection: " + con); //Get a Statement object stmt = con.createStatement(); //Create the new database stmt.executeUpdate( "CREATE DATABASE JunkDB"); stmt.executeUpdate( "GRANT SELECT,INSERT,UPDATE,DELETE," + "CREATE,DROP " + "ON JunkDB.* TO 'auser'@'localhost' " + "IDENTIFIED BY 'drowssap';"); con.close(); }catch( Exception e ) { e.printStackTrace(); }//end catch }//end main }//end class Jdbc00 But it gave the following error D:\Java12\Explore>java Jdbc00 java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at Jdbc11.main(Jdbc00.java:11) Could anyone please guide me in correcting this?

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  • Interface "not marked with serializable attribute" exception

    - by Joel in Gö
    I have a very odd exception in my C# app: when trying to deserialize a class containing a generic List<IListMember> (where list entries are specified by an interface), an exception is thrown reporting that "the type ...IListMember is not marked with the serializable attribute" (phrasing may be slightly different, my VisualStudio is not in English). Now, interfaces cannot be Serializable; the class actually contained in the list, implementing IListMember, is [Serializable]; and yes, I have checked that IListMember is in fact defined as an interface and not accidentally as a class! I have tried reproducing the exception in a separate test project only containing the class containing the List and the members, but there it serializes and deserializes happily :/ Does anyone have any good ideas about what it could be?

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  • CruiseControl .Net Plugin Vb.net Error

    - by Brian
    I am trying to make my own Labeller plugin for Cruise Control .Net 1.4.3. I have made a class based on another plug in example but I keep getting an error Class 'AssemblyVersionLabeller' must implement 'Function Generate(integrationResult As IIntegrationResult) As String' for interface 'ThoughtWorks.CruiseControl.Core.ILabeller' Here is my code : Imports Exortech.NetReflector Imports ThoughtWorks.CruiseControl.Core Imports ThoughtWorks.CruiseControl.Core.Util Namespace NetAssembly.CCNet.Label _ Public Class AssemblyVersionLabeller Implements ILabeller Public Sub Run(ByVal result As IIntegrationResult) result.Label = Generate(result) End Sub Public Function Generate(ByVal integrationResult As IIntegrationResult) As String Dim label As String = integrationResult.LastIntegration.Label Return label End Function <ReflectorProperty("prefix", Required:=False)> _ Public Prefix As String = String.Empty End Class End Namespace What am I doing wrong? What have I missed? Background Info: I am using VS2005. I cant use CrusieControl 1.4.4 RC2 (which has an Assembly Labeller) because my source control's plugin (SCM Anywhere) doesnt work with it.

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  • Iphone: TabView + TableView

    - by OneTrickPonySoft
    I think I'm missing something simple, but I can't figure out exactly what it is. I'm trying to set up an App with a UITabViewController, and one of the Tabs will have a UITableView and UISearchBar (but no Navigation Controller). I set up the UITabViewController with all the tabs in interface builder, and the views are in their own xib files. The xib file for the tab with the UITableView is set up and connected as follows. Stuff in the browser: File's owner (Class is my custom class that is a child of UITableViewController) view - View View (class UIView, reference view - File's owner) contains: UITableView (if i try and set references to the data source / delegate, the app breaks) UISearchBar (unconfigured at the moment) This setup displays all the items and doesn't lock up, but I can't assign a DataSource without it crashing when i try and load the tab with the UITableView. What should I do to get data into this table, either in IB or code? My ideas are as follows: Implement custom UITableView class, hook up to table view in IB or to custom tableviewcontroller in Xcode. Pound head or laptop against the wall until it works. Update: Here's the error the simulator pushes to the console when I connect the Tableview's data source and delegate to File Owner (who's class is my custom tableviewcontroller). 2/14/09 6:59:12 PM TabBarWillbeRight[33172] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x523760'

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  • Nhibernat mapping aspnet_Users table

    - by Michael D. Kirkpatrick
    My User table I want to map to aspnet_Users: <class name="User" table="`User`"> <id name="ID" column="ID" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <property name="UserId" column="UserId" type="Guid" not-null="true" /> <property name="FullName" column="FullName" type="String" not-null="true" /> <property name="PhoneNumber" column="PhoneNumber" type="String" not-null="false" /> </class> My aspnet_Users table: <class name="aspnet_Users" table="aspnet_Users"> <id name="ID" column="UserId" type="Guid" /> <property name="UserName" column="UserName" type="string" not-null="false" /> </class> I tried adding one-to-one, one-to-many and many-to-one mappings. The closest I can get is with this error: Object of type 'System.Guid' cannot be converted to type 'System.Int32'. How do I create a 1 way mapping from User to aspnet_User via the UserId column in User? I am only wanting to create a reference so I can extract read-only information, affect sorts, etc. I still need to leave UserId column in User set up like it is now. Maybe a virtual reference keying off of UserId? Is this even possible with Nhibernate? Unfortunately it acts like it only wants to use ID from User to map to aspnet_Users. Changing the table User to have it's primary key be UserId instead of ID is not an option at this point. Any help would be greatly appreciated. Thanks in advance.

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  • No Binary File Generation

    - by Nathan Campos
    I've just bought a new laptop for me on the travel, then on my free time, I've started to test MinGW on it by trying to compile my own OS that is written in C++, then I've created all the files needed and the kernel.cpp: extern "C" void _main(struct multiboot_data* mbd, unsigned int magic); void _main( struct multiboot_data* mbd, unsigned int magic ) { char * boot_loader_name =(char*) ((long*)mbd)[16]; /* Print a letter to screen to see everything is working: */ unsigned char *videoram = (unsigned char *) 0xb8000; videoram[0] = 65; /* character 'A' */ videoram[1] = 0x07; /* forground, background color. */ } And tried to compile it with g++ G: g++ -o C:\kernel.o -c kernel.cpp -Wall -Wextra -Werror -nostdlib -nostartfiles -nodefaultlibs kernel.cpp: In function `void _main(multiboot_data*, unsigned int)': kernel.cpp:8: warning: unused variable 'boot_loader_name' kernel.cpp: At global scope: kernel.cpp:4: warning: unused parameter 'magic' G: But it don't create any binary file at C:/, what can I do?

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  • Why is a fixed size buffers (arrays) must be unsafe?

    - by brickner
    Let's say I want to have a value type of 7 bytes (or 3 or 777). I can define it like that: public struct Buffer71 { public byte b0; public byte b1; public byte b2; public byte b3; public byte b4; public byte b5; public byte b6; } A simpler way to define it is using a fixed buffer public struct Buffer72 { public unsafe fixed byte bs[7]; } Of course the second definition is simpler. The problem lies with the unsafe keyword that must be provided for fixed buffers. I understand that this is implemented using pointers and hence unsafe. My question is why does it have to be unsafe? Why can't C# provide arbitrary constant length arrays and keep them as a value type instead of making it a C# reference type array or unsafe buffers?

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  • Fluent NHibernate mapping List<Point> as value to single column

    - by Paja
    I have this class: public class MyEntity { public virtual int Id { get; set; } public virtual List<Point> Vectors { get; set; } } How can I map the Vectors in Fluent NHibernate to a single column (as value)? I was thinking of this: public class Vectors : ISerializable { public List<Point> Vectors { get; set; } /* Here goes ISerializable implementation */ } public class MyEntity { public virtual int Id { get; set; } public virtual Vectors Vectors { get; set; } } Is it possible to map the Vectors like this, hoping that Fluent NHibernate will initialize Vectors class as standard ISerializable? Or how else could I map List<Point> to a single column? I guess I will have to write the serialization/deserialization routines myself, which is not a problem, I just need to tell FNH to use those routines. I guess I should use IUserType or ICompositeUserType, but I have no idea how to implement them, and how to tell FNH to cooperate.

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  • rails HABTM versus view (formtastic)

    - by VP
    I have two models: The model NetworkObject try to describe "hosts". I want to have a rule with source and destination, so i'm trying to use both objects from the same class since it dont makes sense to create two different classes. class NetworkObject < ActiveRecord::Base attr_accessible :ip, :netmask, :name has_many :statements has_many :rules, :through =>:statements end class Rule < ActiveRecord::Base attr_accessible :active, :destination_ids, :source_ids has_many :statements has_many :sources, :through=> :statements, :source=> :network_object has_many :destinations, :through => :statements, :source=> :network_object end To build the HABTM i did choose the Model JOIN. so in this case i created a model named Statement with: class Statement < ActiveRecord::Base attr_accessible :source_id, :rule_id, :destination_id belongs_to :network_object, :foreign_key => :source_id belongs_to :network_object, :foreign_key => :destination_id belongs_to :rule end The problem is: is right to add two belongs_to to the same class using different foreign_keys? I tried all combinations like: belongs_to :sources, :class_name => :network_object, :foreign_key => :source_id but no success.. anything that i am doing wrong?

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  • What is the correct term for the number of bits used by an operating system

    - by benc
    Recently, some discussions came up about 32 bit vs. 64 bit implementations of operating systems. While I was composing a message about this topic, I realized that I did not know if there was a correct term for the number of bits supported by an operating system. For example, various versions of Solaris and Linux have 32bit and 64bit releases. Is the distinction "architecture"? In my experience, that has referred to chip types (Intel vs. PPC). Is it a "release"? Typically, I think of a release as a version number a consistent feature set, that might run on different architectures. Maybe it is just "architecture", after all, even though a chip family might have used several different bit sizes over time, the chips themselves are different when you jump from 32bit to 64bit.

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  • NHibernate Unique Constraint on Name and Parent Object fails because NH inserts Null

    - by James
    Hi, I have an object as follows Public Class Bin Public Property Id As Integer Public Property Name As String Public Property Store As Store End Class Public Class Store Public Property Id As Integer Public Property Bins As IEnumerable(Of Bin) End Class I have a unique constraint in the database on Bin.Name and BinStoreID to ensure unique names within stores. However, when NHibernate persists the store, it first inserts the Bin records with a null StoreID before performing an update later to set the correct StoreID. This violates the Unique Key If I persist two stores with a Bin of the same name because The Name columns are the same and the StoreID is null for both. Is there something I can add to the mapping to ensure that the correct StoreID is included in the INSERT rather than performing an update later? We are using HiLo identity generation so we are not relying on DB generated identity columns Thanks James

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  • jQuery Tools alert works once (but only once)

    - by Jim Miller
    I'm trying to build a simple alert mechanism with jQuery Tools -- in response to a bit of Javascript code, pop up an overlay with a message and an OK button that, when clicked, makes the overlay go away. Trivial, or it should be. I've been slavishly following http://flowplayer.org/tools/demos/overlay/trigger.html, and have something that works fine the first time it's invoked, but only that time. If I repeat the JS action that should expose the overlay, it doesn't. My content/DIV: <div class='modal' id='the_alert'> <div id='modal_content' class='modal_content'> <h2>hi there</h2> this is the body <p> <button class='close'>OK</button> </p> </div> <div id='modal_background' class='modal_background'><img src='/images/overlay/f9f9f9-180.png' class='stretch' alt='' /></div> </div> and the Javascript: function showOverlayDialog() { $('#the_alert').overlay({ mask: {color: '#cccccc', loadSpeed: 200, opacity: 0.9}, closeOnClick: false, load: true }); } As I said: When showOverlayDialog() is invoked the first time, the overlay appears just like it should, and goes away when the "OK" button is clicked. But if I cause showOverlayDialog() to run again, without reloading the page, nothing happens. If I reload the page, then the pattern repeats -- the first invocation brings up the overlay, but the second one doesn't. I'm obviously missing something -- any advice out there? Thanks!

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  • C# Design Layout/Patterns

    - by wpfwannabe
    I am still fairly new to C# and I am trying to decide the best way to structure a new program. Here is what I want to do and I would like feed back on my idea. Presentation Layer Business Layer (Separate Class Library) Data Layer (Separate Class Library) Model Layer (Separate Class Library) What I am struggling with is if it is ok to have the classes in the Data Layer and Business Layer inherit from the types I define in Model Layer. This way I can extended the types as needed in my Business Layer with any new properties I see fit. I might not use every property from the Model type in my Business Layer class but is that really a big deal? If this isn't clear enough I can try and put together an example.

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  • Video/Audio frame as input to OpenCore

    - by Vinay
    I am not able to use MediaPlayer/VideoView to make rtsp to work in Android. So I have created a client to interact with RTSP server, I have succeeded in doing this. I am able to get the video/audio frame from RTSP server (MySpace) in Android. Now I want to play the frames. I have searched OpenCore APIs to play the frames, but didn't get any APIs. My investigation: There is a class PlayerDriver.c It creates two sinks one audio and other video. handleSetVideoSurface handleSetAudioSink Two objects of type PVPlayerDataSinkPVMFNode are created. I suspect this class has a way to give the stream as input, but I am not getting the definition of this class. Can you suggest me is there any class I need to look into it?

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  • String::New: what is it?

    - by JavaMan
    I am from a Java background and is learning C++. I encountered the following C++ code: String source = String::New("'Hello' + ', World'"); As what I understand so far, this should be a call to static member function 'New' of class 'String'. But, I've searched through the whole header file defining 'String', there is not any static member named 'New' in the String class or its super classes. Is there any special meaning attached to String class or the New member function in C++?

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  • How to delay static initialization within a property

    - by Mystagogue
    I've made a class that is a cross between a singleton (fifth version) and a (dependency injectable) factory. Call this a "Mono-Factory?" It works, and looks like this: public static class Context { public static BaseLogger LogObject = null; public static BaseLogger Log { get { return LogFactory.instance; } } class LogFactory { static LogFactory() { } internal static readonly BaseLogger instance = LogObject ?? new BaseLogger(null, null, null); } } //USAGE EXAMPLE: //Optional initialization, done once when the application launches... Context.LogObject = new ConLogger(); //Example invocation used throughout the rest of code... Context.Log.Write("hello", LogSeverity.Information); The idea is for the mono-factory could be expanded to handle more than one item (e.g. more than a logger). But I would have liked to have made the mono-factory look like this: public static class Context { private static BaseLogger LogObject = null; public static BaseLogger Log { get { return LogFactory.instance; } set { LogObject = value; } } class LogFactory { static LogFactory() { } internal static readonly BaseLogger instance = LogObject ?? new BaseLogger(null, null, null); } } The above does not work, because the moment the Log property is touched (by a setter invocation) it causes the code path related to the getter to be executed...which means the internal LogFactory "instance" data is always set to the BaseLogger (setting the "LogObject" is always too late!). So is there a decoration or other trick I can use that would cause the "get" path of the Log property to be lazy while the set path is being invoked?

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  • nested QMap in qt

    - by goutham
    I am trying to use this code in my QT app QMap<QString,QMap> but there is a build problem it says C:/****/****/****/***/domparser.h:14: error: type/value mismatch at argument 2 in template parameter list for 'template<class Key, class T> class QMap'

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  • Question about the Cloneable interface and the exception that should be thrown

    - by Nazgulled
    Hi, The Java documentation says: A class implements the Cloneable interface to indicate to the Object.clone() method that it is legal for that method to make a field-for-field copy of instances of that class. Invoking Object's clone method on an instance that does not implement the Cloneable interface results in the exception CloneNotSupportedException being thrown. By convention, classes that implement this interface should override Object.clone (which is protected) with a public method. See Object.clone() for details on overriding this method. Note that this interface does not contain the clone method. Therefore, it is not possible to clone an object merely by virtue of the fact that it implements this interface. Even if the clone method is invoked reflectively, there is no guarantee that it will succeed. And I have this UserProfile class: public class UserProfile implements Cloneable { private String name; private int ssn; private String address; public UserProfile(String name, int ssn, String address) { this.name = name; this.ssn = ssn; this.address = address; } public UserProfile(UserProfile user) { this.name = user.getName(); this.ssn = user.getSSN(); this.address = user.getAddress(); } // get methods here... @Override public UserProfile clone() { return new UserProfile(this); } } And for testing porpuses, I do this in main(): UserProfile up1 = new UserProfile("User", 123, "Street"); UserProfile up2 = up1.clone(); So far, no problems compiling/running. Now, per my understanding of the documentation, removing implements Cloneable from the UserProfile class should throw an exception in up1.clone() call, but it doesn't. I've read around here that the Cloneable interface is broken but I don't really know what that means. Am I missing something?

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  • Rails 3 equivalent of complex SQL query

    - by Bryan
    Given the following models: class Recipe < ActiveRecord::Base has_many :recipe_ingredients has_many :ingredients, :through => :recipe_ingredients end class RecipeIngredient < ActiveRecord::Base belongs_to :recipe belongs_to :ingredient end class Ingredient < ActiveRecord::Base end How can I perform the following SQL query using Arel in Rails 3? SELECT * FROM recipes WHERE NOT EXISTS ( SELECT * FROM ingredients WHERE name IN ('chocolate', 'cream') AND NOT EXISTS ( SELECT * FROM recipe_ingredients WHERE recipe_ingredients.recipe_id = recipes.id AND recipe_ingredients.ingredient_id = ingredients.id))

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  • Static string variable in Objective C on iphone

    - by Prajakta
    Hi, How to create & access static string in iPhone (objective c)? I declare static NSString *str = @"OldValue" in class A. If i assign some value to this in class B as str = @"NewValue". This value persists for all methods in class B. But if I access it in class C (after assignment in B) I am getting it as OldValue. Am I missing something? Should i use extern in other classes? Thanks & Regards, Yogini

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