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  • Should downcasting be avoided while using a class hierarchy in C++?

    - by neuviemeporte
    Let's say I'm writing an application which works with projects, and exposes different functionality depending on the type of the project. I have a hierarchy of classes for the different types of projects: class AbstractProject { }; class ProjectA : public AbstractProject { }; class ProjectB : public AbstractProject { }; class ProjectC : public AbstractProject { }; Now, I was planning to have an AbstractProject *_currentProject pointer as a member in the application's main class, pop up a dialog box on startup and based on the selection, do: _currentProject = new ProjectB(); // e.g. Later, I'll have to downcast the pointer to the specific type to utilize the functionality specific to different Project-s. Somehow this makes me feel uneasy. Is there a Better Way of doing this?

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  • Check one element on last row of a table is not empty using Jquery.

    - by Cesar Lopez
    I have the following function: var emptyFields = false; function checkNotEmpty(tblName, columns, className){ emptyFields = false; $("."+className+"").each(function() { if($.trim($(this).val()) === "" &amp;&amp; $(this).is(":visible")){ emptyFields = true; return false; // break out of the each-loop } }); if (emptyFields) { alert("Please fill in current row before adding a new one."); } else { AddRow_OnButtonClick(tblName,columns); } } Its checking that all elements in the table are not empty before adding a new row, and I only need to check that the last row of the table has at least an element which its not empty and not the whole table. Any help would be apreciated. Thanks

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  • IPhone: Controllers, Delagates, DataSources, etc all in one class?

    - by MLS
    Hi All, I am learning iPhone programming. I am starting with a simple example of displaying recently used documents in a UITableView. What I am confused about is why do I need to have several classes and why cant I just use one? Example, My class is called RecentFileList. I need to implement controller, delegate and datasource as well as the actual table view. Can't I just do this all in my RecentFileList Class versus having to create a RecentFileListDelegate RecentFileListController, RecentFileListDataSource class, etc, etc. Related to this can one define a class like: @interface FileListView : NSObject <UITableViewDelegate> <UITableViewController> <UITableViewDataSource { // code } @end or would I just do the work to make my class a delegate and controller in init()?

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  • How do I create an empty file in emacs?

    - by Singletoned
    How can I create an empty file from emacs, ideally from within a dired buffer? For example, I've just opened a Python module in dired mode, created a new directory, opened that in dired, and now need to add an empty __init__.py file in the directory. If I use C-x C-f __init__.py RET C-x C-s then emacs doesn't create the file because no changes have been made to it. I would have to type in the file, save it, delete my typing and then save it again for that to work. Thanks

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  • Can a function/class know the context from where it is being invoked or instantiated?

    - by vrode
    Let's take this class as example and assume that get_context() returns the source of the call: class A { public function __construct( ) { if( get_class( get_context( ) ) == B ) { return true; } else { return false; } } } class B { function __construct( ) { $a = new A( ); } } $a = new B( ); // returns true, as B is the invoking class of A $a = new A( ); // returns false, as B is invoked outside of any class So, my questions are: 1) can a function know the context that calls it? 2) can a object know context from where it has been instantiated? Or am I dreaming up new features not implementable in PHP?

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  • How to get or Kill all instances from certain class?

    - by Ehab Sutan
    How can I get all instances from a certain class or kill all instances of certain class? For Example, I've a Class MyClass which I intantiate three times as m1, m2 and m3. Is there a way to get or kill all these instances? more clarification : when I've a "settings form" class. When the user click Settings button the application makes instance from this class. When he clicks the same button again it makes new instance. I want it show the 1st instance only and not making new instance

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  • StructureMap: How can i unit test the registry class?

    - by Marius
    I have a registry class like this: public class StructureMapRegistry : Registry { public StructureMapRegistry() { For<IDateTimeProvider>().Singleton().Use<DateTimeProviderReturningDateTimeNow>(); } I want to test that the configuration is according to my intent, so i start writing a test: public class WhenConfiguringIOCContainer : Scenario { private TfsTimeMachine.Domain.StructureMapRegistry registry; private Container container; protected override void Given() { registry = new TfsTimeMachine.Domain.StructureMapRegistry(); container = new Container(); } protected override void When() { container.Configure(i => i.AddRegistry(registry)); } [Then] public void DateTimeProviderIsRegisteredAsSingleton() { // I want to say "verify that the container contains the expected type and that the expected type // is registered as a singleton } } How can verify that the registry is accoring to my expectations? Note: I introduced the container because I didn't see any sort of verification methods available on the Registry class. Idealy, I want to test on the registry class directly.

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  • Getting set accessor for property in abstract class, not possible?

    - by Lars Udengaard
    Given the class': public abstract class AbstractEntity { public virtual Guid Id { get; private set; } } public class Entity { public virtual Guid Id { get; private set; } } And a PropertyInfo for the property 'Id'. When calling the method: PropertyInfo.GetAccessors() It returns both the get-method and the set-method when the class is not abstract (Entity), but only the get-method when the class is abstract (AbstractEntity). Why is this? And is there another way to get the set-method from a property with a private set?

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  • use file or class for documenting classes in doxygen?

    - by AlejandroVK
    Hi all, This surely is a noob question, but I can't find an answer in Doxygen documentation. I'm not sure whether using: @file or @class when documenting my header files. The reason is that if I put file, then all the comments appear in the Files tab only, but not in the Classes tab (per each). For cpp it's ok, I just use file and it's good, but if I use both file and class in the header (file at the beginning and class right before the start of the class declaration) then I get duplicated entries for the class in the generated documentation... What I'm doing wrong? Any suggestions? Ideas? Regards, Alex

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  • How do I stop and empty tag in XML serializer?

    - by John
    I have an object like this, public class UserObj { public string First {get; set;} public string Last {get; set;} public addr Address {get; set;} } public class addr { public street {get; set;} public town {get; set;} } Now when I use XmlSerializer on it and street and town are empty I get this in the XML output, <Address /> Is there a way not to output this empty tag? Thanks

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  • String.split() - matching leading empty String prior to first delimiter?

    - by tehblanx
    I need to be able to split an input String by commas, semi-colons or white-space (or a mix of the three). I would also like to treat multiple consecutive delimiters in the input as a single delimiter. Here's what I have so far: String regex = "[,;\\s]+"; return input.split(regex); This works, except for when the input string starts with one of the delimiter characters, in which case the first element of the result array is an empty String. I do not want my result to have empty Strings, so that something like, ",,,,ZERO; , ;;ONE ,TWO;," returns just a three element array containing the capitalized Strings. Is there a better way to do this than stripping out any leading characters that match my reg-ex prior to invoking String.split? Thanks in advance!

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  • Class decorator to declare static member (e.g., for log4net)?

    - by Ken
    I'm using log4net, and we have a lot of this in our code: public class Foo { private static readonly ILog log = LogManager.GetLogger(typeof(Foo)); .... } One downside is that it means we're pasting this 10-word section all over, and every now and then somebody forgets to change the class name. The log4net FAQ also mentions this alternative possibility, which is even more verbose: public class Foo { private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); ... } Is it possible to write a decorator to define this? I'd really like to say simply: [LogMe] // or perhaps: [LogMe("log")] public class Foo { ... } I've done similar things in other languages, but never a statically-compiled language like C#. Can I define class members from a decorator?

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  • How do I extend the code igniter controller class?

    - by ChronoFish
    Hello, In my CI system\libraries directory I have a new class named DD_Controller.php. This file looks like this: <?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); class DD_Controller extends Controller { protected $ddauthentication; function __construct() { parent::Controller(); $this->ddauthentication = "Authenticated"; } } ?> My application controller is defined like this: class Inquiry extends DD_Controller {...} The Inquiry class works fine when I extend Controller, but I get a Fatal error: Class 'DD_Controller' not found in C:\development\localhost\applications\inquiry\controllers\inquiry.php on line 4 When I extend DD_Controller. In the config file I have the prefix defined as such: $config['subclass_prefix'] = 'DD_'; Any idea of what I'm missing? TIA

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  • Is setting an empty/blank DNS A record allowed?

    - by John
    I'm trying to wrap my head around the wonderful world on DNS. I have created a zone file for example.com which contains: @ A 1.2.3.4 * A 1.2.3.4 However I am also setting up my local DNS, local.example.com which I have created a separate zone file for containing the following: machine1 A 192.168.0.1 machine2 A 192.168.0.2 When I dig machine1.local.example.com it returns A record 192.168.0.1, great. Sadly, badmachine.local.example.com returns 1.2.3.4, as does local.example.com. I'm not sure of the best way to prevent this. If I add the following to the local.example.com empty A records are returned for the above 2 examples as is the behaviour I desire: @ A * A Is this allowed? Is this best practice, or am I doing things terribly wrong? I'm using PowerDNS with BIND backend. Thanks for your thoughts!

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  • C# Why does code compile fine when there is an ambiguous virtual method?

    - by Jimbo
    I have a class (Class B) that inherits another class (Class A) that contains virtual methods. Mistakenly, I omitted the override keyword when declaring a (supposed to be) overriding method in Class B. Class A public class ClassA{ public virtual void TestMethod(){ } } Class B public class ClassB : ClassA{ public void TestMethod(){ } } The code compiled without a problem. Can anyone explain why?

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  • git - how do I clone into a non-empty directory?

    - by shovas
    I have directory A with files matching directory B. Directory A may have other needed files. Directory B is a git repo. I want to clone directory B to directory A but git-clone won't allow me to since the directory is non-empty. I was hoping it would just clone .git and since all the files match I could go from there? I can't clone into an empty directory because I have files in directory A that are not in directory B and I want to keep them. Copying .git is not an option since I want refs to push/pull with and I don't want to set them up manually. Is there any way to do this? Update: I think this works, can anyone see any problems? -- cd a git clone --no-hardlinks --no-checkout ../b a.tmp mv a.tmp/.git . rm -rf a.tmp git unstage # apparently git thinks all the files are deleted if you don't do this

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  • When using SELECT can you modify the value of a returned field based on other fields?

    - by user570759
    When using MySQL SELECT can you change the value of a returned field based on other fields? For example, if I have this select: SELECT city,state,country FROM table Now if city is empty AND state is empty, I want the value of country to returned empty as well (whether country actually has a value or not). Example table: id | city | state | country ----------------------------- 1 | Here | There | MyCountry 2 | | | YourCountry So with the above table, I want the results for id=1 to return Here,There,MyCountry but the results for id=2 should be empty,empty,empty Thanks

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  • In Django, using __init__() method of non-abstract parent model to record class name of child model

    - by k-g-f
    In my Django project, I have a non-abstract parent model defined as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) and, say, two children models defined as follows: class ChildA(Parent): parent = models.OneToOneField(Parent,parent_link=True) class ChildB(Parent): parent = models.OneToOneField(Parent,parent_link=True) Each time I create an instance of ChildA or of ChildB, I'd like the classType attribute to be set to the strings "ChildA" or "ChildB" respectively. What I have done is added an _ _ init_ _() method to Parent as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) def __init__(self,*args,**kwargs): super(Parent,self).__init__(*args,**kwargs) self.classType = self.__class__.__name__ Is there a better way to implement and achieve my desired result? One downside of this implementation is that when I have an instance of the Parent, say "parent", and I want to get the type of the child object linked with "parent", calling "parent.classType" gives me "Parent". In order to get the appropriate "ChildA" or "ChildB" value, I need to write a "_getClassType()" method to wrap a custom sql query.

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  • Why does Generic class signature requires specifying new() if type T needs instantiation ?

    - by this. __curious_geek
    I'm writing a Generic class as following. public class Foo<T> : where T : Bar, new() { public void MethodInFoo() { T _t = new T(); } } As you can see the object(_t) of type T is instantiated at run-time. To support instantiation of generic type T, language forces me to put new() in the class signature. I'd agree to this if Bar is an abstract class but why does it need to be so if Bar standard non-abstract class with public parameter-less constructor. compiler prompts following message if new() is not found. Cannot create an instance of the variable type 'T' because it does not have the new() constraint

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  • Setting an empty default value for a char-column in MySQL?

    - by user281434
    Hi In phpMyAdmin I have a char(32) column that has no default value(ie. Default: None). When I try to insert data through a SQL query, it throws out an error saying that the column "doesn't have a default value". I need it to be empty, so instead I've just set it's default value as "As defined: " and then nothing in the value field. Is this a bad idea? And is it any better than simply throwing in an empty value for the column in the SQL query? Thanks for your time.

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  • NameError on accessing ancestor constants when using Class.new?

    - by PDG
    To my current knowledge Ruby classes defined with Class.new should not differ from classes created with the class keyword. Then why do following classes B and C behave differently? class A TEST = 'A' def test TEST end end class B < A def test TEST end end C = Class.new(A) { def test TEST end } puts 'A: ' + A.new.test # => "A: A" puts 'B: ' + B.new.test # => "B: A" puts 'C: ' + C.new.test # => uninitialized constant TEST (NameError) Tested with ruby 1.9.3p327 and ruby 1.8.7p358.

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  • Auto-Selecting Navigation works for active page but how to add class to parent menu items?

    - by jacqueschoquette
    I am following this article http://docs.jquery.com/Tutorials:Auto-Selecting_Navigation I am able to successfully add a class to the active page li menu item but does anyone know how to modify or add to this script so that any parent menu li items also get the active class? I would like to avoid having to add ID's as the menu items will be changing alot My menus have three levels max here is the script jquery script i am using $(function(){ var path = location.pathname.substring(1); if ( path ) $('.topLevel a[href$="' + path + '"]').attr('class', 'underline'); }); which works on the current page li a I thought I could go this route $('.topLevel a[href$="' + path + '"]').attr('class', 'underline').parent().attr('class', 'underline'); but it does not seem to work any ideas? a working example can be found here whistlerwebandprint.com/home.html

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  • MySQL null/empty-string too long for VarChar(5) ?

    - by rlb.usa
    I have a stored procedure that takes an input var_zip varchar(5). My webapp calls this procedure and gives it the parameter: cmd.Parameters.Add(new MySqlParameter("var_Zip", MySqlDbType.VarChar, 5)); cmd.Parameters["var_Zip"].Value = txtZip.Text; txtZip is empty. So it is either giving empty string '', or null. Doesn't matter to me which. But it is throwing an error: MySql.Data.MySqlClient.MySqlException: Data too long for column 'var_Zip' at row 1 What's going on and how can I fix it? I don't understand.

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  • Is Java class initialized by the thread which use it for the first time?

    - by oo_olo_oo
    Lets assume following classes definition: public class A { public final static String SOME_VALUE; static { SOME_VALUE = "some.value"; } } public class B { private final String value = A.SOME_VALUE; } Assuming that the class A hasn't been loaded yet, what does happen when object of the class B is instantiated by some thread T? The class A has to be loaded and instantiated first. But my question is: if it's done in context of the thread T, or rather in context of some other (special) "classloader" thread?

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