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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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• 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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• 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 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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• 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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• 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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• vc++ - static member is showing error

  - by prabhakaran

  I am using vc++(2010). I am trying to create a class for server side socket. Here is the header file #include<winsock.h> #include<string> #include<iostream> using namespace std; class AcceptSocket { // static SOCKET s; protected: SOCKET acceptSocket; public: AcceptSocket(){}; void setSocket(SOCKET socket); static void EstablishConnection(int portNo,string&); static void closeConnection(); static void StartAccepting(); virtual void threadDeal(); static DWORD WINAPI MyThreadFunction(LPVOID lpParam); }; SOCKET AcceptSocket::s; and the corresponding source file #include<NetWorking.h> #include<string> void AcceptSocket::setSocket(SOCKET s) { acceptSocket=s; } void AcceptSocket::EstablishConnection(int portno,string &failure) { WSAData w; int error = WSAStartup(0x0202,&w); if(error) failure=failure+"\nWSAStartupFailure"; if(w.wVersion != 0x0202) { WSACleanup(); failure=failure+"\nVersion is different"; } SOCKADDR_IN addr; addr.sin_family=AF_INET; addr.sin_port=htons(portno); addr.sin_addr.s_addr=htonl(INADDR_ANY); AcceptSocket::s=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP); if(AcceptSocket::s == INVALID_SOCKET) failure=failure+"\nsocket creating error"; if(bind(AcceptSocket::s,(LPSOCKADDR) &addr,sizeof(addr)) == SOCKET_ERROR) failure=failure+"\nbinding error"; listen(AcceptSocket::s,SOMAXCONN); } void AcceptSocket::closeConnection() { if(AcceptSocket::s) closesocket(AcceptSocket::s); WSACleanup(); } void AcceptSocket::StartAccepting() { sockaddr_in addrNew; int size=sizeof(addrNew); while(1) { SOCKET temp=accept(AcceptSocket::s,(sockaddr *)&addrNew,&size); AcceptSocket * tempAcceptSocket=new AcceptSocket(); tempAcceptSocket->setSocket(temp); DWORD threadId; HANDLE thread=CreateThread(NULL,0,MyThreadFunction,(LPVOID)tempAcceptSocket,0,&threadId); } } DWORD WINAPI AcceptSocket::MyThreadFunction(LPVOID lpParam) { AcceptSocket * acceptsocket=(AcceptSocket *) lpParam; acceptsocket->threadDeal(); return 1; } void AcceptSocket::threadDeal() { "You didn't define threadDeal in the derived class"; } Now the main.cpp is #include<Networking.h> int main() { } When I am compiling The error I got is Error 1 error LNK2005: "private: static unsigned int AcceptSocket::s" (?s@AcceptSocket@@0IA) already defined in NetWorking.obj C:\Documents and Settings\prabhakaran\Desktop\check\check\main.obj check Error 2 error LNK1169: one or more multiply defined symbols found C:\Documents and Settings\prabhakaran\Desktop\check\Debug\check.exe 1 1 check Now anybody please enlighten me about this issue

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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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• 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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• Make methods that do not depend on instance fields, static?

  - by m3th0dman

  Recently I started programming in Groovy for a integration testing framework, for a Java project. I use Intellij IDEA with Groovy plug-in and I am surprised to see as a warning for all the methods that are non-static and do not depend on any instance fields. In Java, however, this is not an issue (at least from IDE's point of view). Should all methods that do not depend onto any instance fields be transformed into static functions? If true, is this specific to Groovy or it is available for OOP in general? And why?

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• C#4: Why does this static field always get initialized over-eagerly?

  - by TheSilverBullet

  I am looking at this excellent article from Jon Skeet at this location: http://csharpindepth.com/Articles/General/Beforefieldinit.aspx 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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• What is the difference between all-static-methods and applying a singleton pattern?

  - by shahensha

  I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton pattern here or rather make all it's methods static? I will be using this DBManager for basic things like adding, deleting and updating User profiles. Along with it, I'll use for all other querying purposes, for instance to find out whether a username already exists and to get all users for administrative purposes and stuff like that. My questions What is the benefit of singleton pattern? Which thing is most apt here? All static methods or a singleton pattern? Please compare both of them. regards shahensha P.S. The database is bigger than this. Here I am talking only about the tables which I'll be using for storing User Information.

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• Requriing static class setter to be called before Constructor, bad design?

  - by roverred

  I have a class, say Foo, and every instance of Foo will need and contain the same List object, myList. Since every class instance will share the same List Object, I thought it would be good to make myList static and use a static function to set myList before the constructor is called. I was wondering if this was bad, because this requires the setter to be called before the constructor. If the person doesn't, the program will crash. Alternative way would be passing myList every time. Thanks.

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• What is the difference between all-static-methods and applying a singleton pattern?

  - by shahensha

  I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton pattern here or rather make all it's methods static? I will be using this DBManager for basic things like adding, deleting and updating User profiles. Along with it, I'll use for all other querying purposes, for instance to find out whether a username already exists and to get all users for administrative purposes and stuff like that. My questions What is the benefit of singleton pattern? Which thing is most apt here? All static methods or a singleton pattern? Please compare both of them. P.S. The database is bigger than this. Here I am talking only about the tables which I'll be using for storing User Information.

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• Configuring Cisco ASA 5510 to assign static IP address based on MAC address

  - by knd

  Hi, We have a CISCO ASA 5510 at work. We want to configure the same such that it can serve specific IP addresses based on the MAC address of the clients. Any help would be greatly appreciated. Thanks in advance -knd

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• Apache - Serving static files from different subdomain + machine

  - by rubayeet

  Here's the scenario A site is running on this domain - www.someserver.com I'm going to host subdomain.someserver.com on my machine. Let's say all the image files are under the directory 'img'. I don't want to copy all their images to my machine. So what should be the Apache directive(s) that'll map the request for an image, like http://subdomain.someserver.com/img/image.png to http://www.someserver.com/img/image.png

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• Static Routes and the Routing Table

  - by TheD

  This is very much a learning question if someone would be happy to explain a couple of concepts. My question is - the default routing table that exists in, in my case, a default Windows 7 install, what do each of the routes in the table do? Here is a screenshot: The 10.128.4.0 is just a route I've added while messing. I understand from a question I posted on Superuser the first route is just a default route that will route all traffic for any IP to my default gateway on my Interface in use. But what about the others? And how would the routing table handle a machine with multiple NIC's, perhaps connected to two different networks, or maybe even two NIC's on the same network so a VM can have a physical Network card instead of each VM sharing the hosts. Thanks!

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• Static Route Qestion

  - by mrlayance

  I have a Wan simulator between 2 networks. I can ping both networks from the wan simulator, but I can not ping from one network to the other. testr01 Fa0/0 10.0.0.1/24 FA0/1 192.168.0.1/30 | | Wan Sim 2 nics Eth0 192.168.0.2/30 | Eth1 192.168.1.2/30 | | testr02 Fa0/1 192.168.1.1/30 Fa0/0 10.1.0.2/24 I can not figure out what type of routes I need. On the route? On the Server? I guess all 10. traffic to the Fa0/0 ports? Thanks

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• Generate static gallery

  - by theomega

  Hy, I need a (linux/shell) script which does the following: It takes a folder full of jpg-files, generates thumbnails and previews (maybe using imagemagik's convert) and creates a html-page which includes all the thumbnails, opens a preview using something like LightBox and links to the original size. Does somebody know a script which does this? I could write one on my own, but it would save me some time.

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• Why are static classes considered “classes” and “reference types”?

  - by Timwi

  I’ve been pondering about the C# and CIL type system today and I’ve started to wonder why static classes are considered classes. There are many ways in which they are not really classes: A “normal” class can contain non-static members, a static class can’t. In this respect, a class is more similar to a struct than it is to a static class, and yet structs have a separate name. You can have a reference to an instance of a “normal” class, but not a static class (despite it being considered a “reference type”). In this respect, a class is more similar to an interface than it is to a static class, and yet interfaces have a separate name. The name of a static class can never be used in any place where a type name would normally fit: you can’t declare a variable of this type, you can’t use it as a base type, and you can’t use it as a generic type parameter. In this respect, static classes are somewhat more like namespaces. A “normal” class can implement interfaces. Once again, that makes classes more similar to structs than to static classes. A “normal” class can inherit from another class. It is also bizarre that static classes are considered to derive from System.Object. Although this allows them to “inherit” the static methods Equals and ReferenceEquals, the purpose of that inheritance is questionable as you would call those methods on object anyway. C# even allows you to specify that useless inheritance explicitly on static classes, but not on interfaces or structs, where the implicit derivation from object and System.ValueType, respectively, actually has a purpose. Regarding the subset-of-features argument: Static classes have a subset of the features of classes, but they also have a subset of the features of structs. All of the things that make a class distinct from the other kinds of type, do not seem to apply to static classes. Regarding the typeof argument: Making a static class into a new and different kind of type does not preclude it from being used in typeof. Given the sheer oddity of static classes, and the scarcity of similarities between them and “normal” classes, shouldn’t they have been made into a separate kind of type instead of a special kind of class?

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• Variables in static library are never initialized. Why?

  - by Coyote

  I have a bunch of variables that should be initialized then my game launches, but must of them are never initialized. Here is an example of the code: MyClass.h class MyClass : public BaseObject { DECLARE_CLASS_RTTI(MyClass, BaseObject); ... }; MyClass.cpp REGISTER_CLASS(MyClass) Where REGISTER_CLASS is a macro defined as follow #define REGISTER_CLASS(className)\ class __registryItem##className : public __registryItemBase {\ virtual className* Alloc(){ return NEW className(); }\ virtual BaseObject::RTTI& GetRTTI(){ return className::RTTI; }\ }\ \ const __registryItem##className __registeredItem##className(#className); and __registryItemBase looks like this: class __registryItemBase { __registryItemBase(const _string name):mName(name){ ClassRegistry::Register(this); } const _string mName; virtual BaseObject* Alloc() = 0; virtual BaseObject::RTTI& GetRTTI() = 0; } Now the code is similar to what I currently have and what I have works flawlessly, all the registered classes are registered to a ClassManager before main(...) is called. I'm able to instantiate and configure components from scripts and auto-register them to the right system etc... The problem arrises when I create a static library (currently for the iPhone, but I fear it will happen with android as well). In that case the code in the .cpp files is never registered. Why is the resulting code not executed when it is in the library while the same code in the program's binary is always executed? Bonus questions: For this to work in the static library, what should I do? Is there something I am missing? Do I need to pass a flag when building the lib? Should I create another structure and init all the __registeredItem##className using that structure?

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• Static method not called

  - by Smile

  I'm trying to call a static method (printABC()) in this class but it's not working. If I uncomment both of the lines marked T_T (1 and 2), it works! Why does it fail with only one of the lines? import java.util.Scanner; class pro0009 { static Scanner in = new Scanner(System.in); static int A,B,C; static void printABC(){ String ABC = in.nextLine(); ABC=ABC.replace("A"," "+A+" "); ABC=ABC.replace("B"," "+B+" "); ABC=ABC.replace("C"," "+C+" "); //System.out.print(ABC.substring(1)); System.out.print(ABC); } public static void main(String[] args){ int x = in.nextInt(); //1 int y = in.nextInt(); //2 int z = in.nextInt(); //3 if(x<y){//1<2 if(x<z){ //1<3 if(y<z){//x<y<z 2<3 //1<2<3 A=x; B=y; C=z; printABC();//T_T 1 System.out.println("Here"); //pro0009.printABC();//T_T 2 //System.out.println("Here2"); }else{ //x<z<y A=x; B=z; C=y; } }else{//z<x<y A=z; B=x; C=y; } }else{//y<x if(y<z){ if(x<z){//y<x<z A=y; B=x; C=z; }else{//y<z<x A=y; B=z; C=x; } }else{//z<y<x A=z; B=y; C=x; } } } }

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• Accessing Static Methods on a Generic class in c#

  - by mrlane

  Hello, I have the following situation in code, which I suspect may be a bit dodgey: I have a class: abstract class DataAccessBase<T> : IDataAccess where T : AnotherAbstractClass This class DataAccessBase also has a static factory method which creates instances of derived classes of itself using an enum value in a which statement to decide which derived type to create: static IDataAccess CreateInstance(TypeToCreateEnum) Now, the types derived from DataAccessBase<T> are themselves NOT generic, they specify a type for T: class PoLcZoneData : DataAccessBase<PoLcZone> // PoLcZone is derived from AnotherAbstractClass So far I am not sure if this is pushing the limits of good use of generics, but what I am really concerned about is how to access the static CreateInstance() method in the first place: The way I am doing this at the moment is to simply pass any type T where T : AnotherAbstractClass. In particular I am passing AnotherAbstractClass itself. This allows compilation just fine, but it does seem to me that passing any type to a generic class just to get at the statics is a bit dodgey. I have actually simplified the situation somewhat as DataAccessBase<T> is the lower level in the inheritance chain, but the static factory methods exists in a middle tier with classes such as PoLcZoneData being the most derived on the only level that is not generic. What are peoples thoughts on this arrangement?

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• Thread-safe initialization of function-local static const objects

  - by sbi

  This question made me question a practice I had been following for years. For thread-safe initialization of function-local static const objects I protect the actual construction of the object, but not the initialization of the function-local reference referring to it. Something like this: namspace { const some_type& create_const_thingy() { lock my_lock(some_mutex); static const some_type the_const_thingy; return the_const_thingy; } } void use_const_thingy() { static const some_type& the_const_thingy = create_const_thingy(); // use the_const_thingy } The idea is that locking takes time, and if the reference is overwritten by several threads, it won't matter. I'd be interested if this is safe enough in practice? safe according to The Rules? (I know, the current standard doesn't even know what "concurrency" is, but what about trampling over an already initialized reference? And do other standards, like POSIX, have something to say that's relevant to this?) For the inquiring minds: Many such function-local static const objects I used are maps which are initialized from const arrays upon first use and used for lookup. For example, I have a few XML parsers where tag name strings are mapped to enum values, so I could later switch over the tags enum values.

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