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  • Uses for static generic classes?

    - by Hightechrider
    What are the key uses of a Static Generic Class in C#? When should they be used? What examples best illustrate their usage? e.g. public static class Example<T> { public static ... } Since you can't define extension methods in them they appear to be somewhat limited in their utility. Web references on the topic are scarce so clearly there aren't a lot of people using them. Here's a couple:- http://ayende.com/Blog/archive/2005/10/05/StaticGenericClass.aspx http://stackoverflow.com/questions/686630/static-generic-class-as-dictionary

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  • Variable declarations in header files - static or not?

    - by Rob
    When refactoring away some #defines I came across declarations similar to the following in a C++ header file: static const unsigned int VAL = 42; const unsigned int ANOTHER_VAL = 37; The question is, what difference, if any, will the static make? Note that multiple inclusion of the headers isn't possible due to the classic #ifndef HEADER #define HEADER #endif trick (if that matters). Does the static mean only one copy of VAL is created, in case the header is included by more than one source file?

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  • Static Property losing its value intermittently ?

    - by joedotnot
    Is there something fundamentally wrong with the following design, or can anyone see why would the static properties sometimes loose their values ? I have a class library project containing a class AppConfig; this class is consumed by a Webforms project. The skeleton of AppConfig class is as follows: Public Class AppConfig Implements IConfigurationSectionHandler Private Const C_KEY1 As String = "WebConfig.Key.1" Private Const C_KEY2 As String = "WebConfig.Key.2" Private Const C_KEY1_DEFAULT_VALUE as string = "Key1defaultVal" Private Const C_KEY2_DEFAULT_VALUE as string = "Key2defaultVal" Private Shared m_field1 As String Private Shared m_field2 As String Public Shared ReadOnly Property ConfigValue1() As String Get ConfigValue1= m_field1 End Get End Property Public Shared ReadOnly Property ConfigValue2() As String Get ConfigValue2 = m_field2 End Get End Property Public Shared Sub OnApplicationStart() m_field1 = ReadSetting(C_KEY1, C_KEY1_DEFAULT_VALUE) m_field2 = ReadSetting(C_KEY2, C_KEY1_DEFAULT_VALUE) End Sub Public Overloads Shared Function ReadSetting(ByVal key As String, ByVal defaultValue As String) As String Try Dim setting As String = System.Configuration.ConfigurationManager.AppSettings(key) If setting Is Nothing Then ReadSetting = defaultValue Else ReadSetting = setting End If Catch ReadSetting = defaultValue End Try End Function Public Function Create(ByVal parent As Object, ByVal configContext As Object, ByVal section As System.Xml.XmlNode) As Object Implements System.Configuration.IConfigurationSectionHandler.Create Dim objSettings As NameValueCollection Dim objHandler As NameValueSectionHandler objHandler = New NameValueSectionHandler objSettings = CType(objHandler.Create(parent, configContext, section), NameValueCollection) Return 1 End Function End Class The Static Properties get set once on application start, from the Application_Start event of the Global.asax Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs) //Fires when the application is started AppConfig.OnApplicationStart() End Sub Thereafter, whenever we want to access a value in the Web.Config from anywhere, e.g. aspx page code-behind or another class or referenced class, we simply call the static property. For example, AppConfig.ConfigValue1() AppConfig.ConfigValue2() This is turn returns the value stored in the static backing fields m_field1, m_field2 Problem is sometimes these values are empty string, when clearly the Web.Config entry has values. Is there something fundamentally wrong with the above design, or is it reasonable to expect the static properties would keep their value for the life of the Application session?

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  • Another Call to a member function get_segment() on a non-object question

    - by hogofwar
    I get the above error when calling this code: <? class Test1 extends Core { function home(){ ?> This is the INDEX of test1 <? } function test2(){ echo $this->uri->get_segment(1); //this is where the error comes from ?> This is the test2 of test1 testing URI <? } } ?> I get the error where commentated. This class extends this class: <?php class Core { public function start() { require("funk/funks/libraries/uri.php"); $this->uri = new uri(); require("funk/core/loader.php"); $this->load = new loader(); if($this->uri->get_segment(1) != "" and file_exists("funk/pages/".$this->uri->get_segment(1).".php")){ include("funk/pages/". $this->uri->get_segment(1).".php"); $var = $this->uri->get_segment(2); if ($var != ""){ $home= $this->uri->get_segment(1); $Index= new $home(); $Index->$var(); }else{ $home= $this->uri->get_segment(1); $Index = new $home(); $Index->home(); } }elseif($this->uri->get_segment(1) and ! file_exists("funk/pages/".$this->uri->get_segment(1).".php")){ echo "404 Error"; }else{ include("funk/pages/index.php"); $Index = new Index(); $Index->home(); //$this->Index->index(); echo "<!--This page was created with FunkyPHP!-->"; } } } ?> And here is the contents of uri.php: <?php class uri { private $server_path_info = ''; private $segment = array(); private $segments = 0; public function __construct() { $segment_temp = array(); $this->server_path_info = preg_replace("/\?/", "", $_SERVER["PATH_INFO"]); $segment_temp = explode("/", $this->server_path_info); foreach ($segment_temp as $key => $seg) { if (!preg_match("/([a-zA-Z0-9\.\_\-]+)/", $seg) || empty($seg)) unset($segment_temp[$key]); } foreach ($segment_temp as $k => $value) { $this->segment[] = $value; } unset($segment_temp); $this->segments = count($this->segment); } public function segment_exists($id = 0) { $id = (int)$id; if (isset($this->segment[$id])) return true; else return false; } public function get_segment($id = 0) { $id--; $id = (int)$id; if ($this->segment_exists($id) === true) return $this->segment[$id]; else return false; } } ?> i have asked a similar question to this before but the answer does not apply here. I have rewritten my code 3 times to KILL and Delimb this godforsaken error! but nooooooo....

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  • noncopyable static const member class in template class

    - by Dukales
    I have a non-copyable (inherited from boost::noncopyable) class that I use as a custom namespace. Also, I have another class, that uses previous one, as shown here: #include <boost/utility.hpp> #include <cmath> template< typename F > struct custom_namespace : boost::noncopyable { F sqrt_of_half(F const & x) const { using std::sqrt; return sqrt(x / F(2.0L)); } // ... maybe others are not so dummy const/constexpr methods }; template< typename F > class custom_namespace_user { static ::custom_namespace< F > const custom_namespace_; public : F poisson() const { return custom_namespace_.sqrt_of_half(M_PI); } static F square_diagonal(F const & a) { return a * custom_namespace_.sqrt_of_half(1.0L); } }; template< typename F > ::custom_namespace< F > const custom_namespace_user< F >::custom_namespace_(); this code leads to the next error (even without instantiation): error: no 'const custom_namespace custom_namespace_user::custom_namespace_()' member function declared in class 'custom_namespace_user' The next way is not legitimate: template< typename F ::custom_namespace< F const custom_namespace_user< F ::custom_namespace_ = ::custom_namespace< F (); What should I do to declare this two classes (first as noncopyable static const member class of second)? Is this feaseble?

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  • what is the exact difference between PHP static class and singleton class

    - by Saif Bechan
    I have always used a Singleton class for a registry object in PHP. As all Singleton classes I think the main method looks like this: class registry { public static function singleton() { if( !isset( self::$instance ) ) { self::$instance = new registry(); } return self::$instance; } public function doSomething() { echo 'something'; } } So whenever I need something of the registry class I use a function like this: registry::singleton()->doSomethine(); Now I do not understand what the difference is between creating just a normal static function. Will it create a new object if I just use a normal static class. class registry { public static function doSomething() { echo 'something'; } } Now I can just use: registry::doSomethine(); Can someone explain to me what the function is of the singleton class. I really do not understand this.

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  • how to deal with a static analyzer output

    - by Jim
    We have started using a static analyzer (Coverity) on our code base. We were promptly stupefied by the sheer amount of warnings we received (its in the hundreds of thousands) , it will take the entire team a few mounts to clear them all (obliviously impossible). the options we discussed so far are 1) hire a contractor to sort out the warning and fix them - he drawback: we will probably need very experiences people to do all these modifications, and no contractor will have required understanding of the code. 2) filter out the warning and deal only with the dangerous ones - the problem here is that our static analysis output will always be cluttered by warning making it difficult for us to isolate problems. also the filtering of the warning is also a major effort. either way, bringing our code to a state when the static analyzer can be a useful tool for us seems a monumental task. so how is it possible to work with the static analyzer without braining current development efforts into a complete stand still?

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  • Serving CSS from a static domain

    - by Saif Bechan
    I want to serve my css and images from a static cookieless domain. Now my problem is how to point to the images from within my css files. I don't want to program my domain hard within the css file, for example: http://static.com/image.png I would rather have a variable pointing to the the image, so it works for every static domain i use. What is the best way for achieving this. Should i run the whole css file trough php and add the static domain in front of all the png references. A downside in this is that i have to place the whole css in html. Or is there another more optimized way of doing this.

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  • What's static function for in c?

    - by user198729
    I only see static methods by which we don't need to instantiate a class to call the method. What's the purpose of a static function? static GtkWidget * create_bbox (gint horizontal, char *title, gint spacing, gint layout) { ... }

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  • Java: when to use static methods

    - by KP65
    Hello, I am wondering when to use static methods? Say If i have a class with a few getters and setters, a method or two, and i want those methods only to be invokable on an instance object of the class. Does this mean i should use a static method? e.g Obj x = new Obj(); x.someMethod or Obj.someMethod (is this the static way?) I'm rather confused!

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  • Why can't you call a non-static method from a static method?

    - by VoodooChild
    I have a static method [Method1] in my class, which calls another method [Method2] in the same class and is not a static method. But this is a no-no. I get this error: An object reference is required for the non-static field, method, or property "ClassName.MethodName()" Can someone please briefly describe why? including other things that might be related to this.

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  • static, define, and const in C

    - by yCalleecharan
    Hi, I've read that static variables are used inside function when one doesn't want the variable value to change/initialize each time the function is called. But what about defining a variable static in the main program before "main" e.g. #include <stdio.h> static double m = 30000; int main(void) { value = m * 2 + 3; } Here the variable m has a constant value that won't get modified later in the main program. In the same line of thought what difference does it make to have these instead of using the static definition: const double m = 30000; or #define m 30000 //m or M and then making sure here to use double operations in the main code so as to convert m to the right data type. Thanks a lot...

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  • Initializing static pointer in templated class.

    - by Anthony
    This is difficult for me to formulate in a Google query (at least one that gives me what I'm looking for) so I've had some trouble finding an answer. I'm sure I'm not the first to ask though. Consider a class like so: template < class T > class MyClass { private: static T staticObject; static T * staticPointerObject; }; ... template < class T > T MyClass<T>::staticObject; // <-- works ... template < class T > T * MyClass<T>::staticPointerObject = NULL; // <-- cannot find symbol staticPointerObject. I am having trouble figuring out why I cannot successfully create that pointer object. Edit: The above code is all specified in the header, and the issue I mentioned is an error in the link step, so it is not finding the specific symbol.

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  • Javascript - cannot make static reference to non-static function ....

    - by Ankur
    I am making a reference to the Javascript function splice() on an array and I get the error: "Cannot make a static reference to the non-static function splice()" What's going on - how is this a static reference, aren't I referencing an instance of an Array class and its method - how is that static? $(document).ready( function() { var queryPreds = new Array(); var queryObjs = new Array(); function remFromQuery(predicate) { for(var i=0; i<arrayName.length;i++ ) { if(queryPreds[i]==predicate) queryPreds.splice(i,1); queryObjs.splice(i,1); } } }

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  • Static variables in C and C++

    - by Naveen
    Is there any difference between a variable declared as static outside any function between C and C++. I read that static means file scope and the variables will not be accessible outside the file. I also read that in C, global variables are static . So does that mean that global variables in C can not be accessed in another file?

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  • Would you make this method Static or not?

    - by Adam Drummond
    During a code review I presented a method quickly to the team that I had made static and one person agreed that there was no reason for it to not be static and a person disagreed saying that he would not make it static because it wasn't necessary and just to be on the safe side for future modifications and testing. So I did quite a bit of research and obviously it's a specialized case but I would like to know what you would do in this situation and why? (Its basically a helper method I call from a few different methods, a very low traffic page. More for my knowledge and learning on Static.) private IEnumerable<Category> GetCategoryByID(int id, Context context) { var categoryQuery = from selectAllProc in context.SelectAll_sp() where selectAllProc.CategoryID == id select selectAllProc; return categoryQuery; }

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  • Unable to access static var from Document Class in AS3

    - by omidomid
    I have a Document class called "CityModule", and an asset with class "City". Below is the coe for each. For some reason, I am unable to access the static variables of the City class from CityModule: CityModule.as: package { public class CityModule extends MovieClip { public function CityModule() { var buildings:Array = City.getBuildings(); } } } } City.as: package { import flash.display.MovieClip; public class City extends MovieClip { private static var _buildings:Array = [ {className:'City.Generic1', type:'generic'}, {className:'City.Generic2', type:'generic'}, {className:'City.Generic3', type:'generic'} ]; public function City(){ //empty } public static function getBuildings():Array{ return _buildings; } } } Doing this gives me a "Call to a possibly undefined method getBuildings" error. If I instantiate an instance of City, I can see any public/ getters/ setters perfectly fine. But static isn't working...

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  • CodeIgniter static class question

    - by Josh K
    If I would like to have several static methods in my models so I can say User::get_registered_users() and have it do something like public static function get_registered_users() { $sql = "SELECT * FROM `users` WHERE `is_registered` = 0"; $this->db->query($sql); // etc... } Is it possible to access the $this->db object or create a new one for a static method?

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  • static member specialization of templated child class and templated base class

    - by b3nj1
    I'm trying to have a templated class (here C) that inherits from another templated class (here A) and perform static member specialization (of int var here), but I cant get the right syntax to do so (if it's possible #include <iostream> template<typename derived> class A { public: static int var; }; //This one works fine class B :public A<B> { public: B() { std::cout << var << std::endl; } }; template<> int A<B>::var = 9; //This one doesn't works template<typename type> class C :public A<C<type> > { public: C() { std::cout << var << std::endl; } }; //template<> template<typename type> int A<C<type> >::a = 10; int main() { B b; C<int> c; return 0; } I put an example that works with a non templated class (here B) and i can get the static member specialization of var, but for C that just doesn't work. Here is what gcc tells me : test.cpp: In constructor ‘C<type>::C()’: test.cpp:29:26: error: ‘var’ was not declared in this scope test.cpp: At global scope: test.cpp:34:18: error: template definition of non-template ‘int A<C<type> >::a’ I'm using gcc version 4.6.3, thanks for any help

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  • C++ static virtual members?

    - by cvb
    Is it possible in C++ to have a member function that is both static and virtual? Apperantly, there isn't a straight-forward way to do it (static virtual member(); is a complie error), but at least a way to acheive the same effect? I.E: struct Object { struct TypeInformation; static virtual const TypeInformation &GetTypeInformation() const; }; struct SomeObject : public Object { static virtual const TypeInformation &GetTypeInformation() const; }; It makes sence to use GetTypeInformation() both on an instance (object->GetTypeInformation()) and on a class (SomeObject::GetTypeInformation()), which can be useful for comparsions and vital for templates. The only ways I can think of involves writing two functions / a function and a constant, per class, or use macros. Any other solutions?

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  • class member access specifiers

    - by pdehaan
    I understand what the typical access specifiers are, and what they mean. 'public' members are accessible anywhere, 'private' members are accessible only by the same class and friends, etc. What I'm wondering is what, if anything, this equates to in lower-level terms. Are their any post-compilation functional differences between these beyond the high-level restrictions (what can access what) imposed by the language (c++ in this case) they're used in. Another way to put it - if this were a perfect world where programmers always made good choices (like not accessing members that may change later and using only well defined members that should stay the same between implementations), would their be any reason to use these things?

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  • Why does this static field always get initialized over-eagerly?

    - by TheSilverBullet
    I am looking at this excellent article from Jon Skeet. While executing the demo code, Jon Skeet says that we can expect three different kinds of behaviours. To quote that article: The runtime could decide to run the type initializer on loading the assembly to start with... Or perhaps it will run it when the static method is first run... Or even wait until the field is first accessed... When I try this out (on framework 4), I always get the first result. That is, the static method is initialized before the assembly is loaded. I have tried running this multiple times and get the same result. (I tried both the debug and release versions) Why is this so? Am I missing something?

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