Search Results

Search found 3766 results on 151 pages for 'singleton scope'.

Page 3/151 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

• javascript singleton question

  - by Shawn

  I just read a few threads on the discussion of singleton design in javascript. I'm 100% new to the Design Pattern stuff but as I see since a Singleton by definition won't have the need to be instantiated, conceptually if it's not to be instantiated, in my opinion it doesn't have to be treated like conventional objects which are created from a blueprint(classes). So my wonder is why not just think of a singleton just as something statically available that is wrapped in some sort of scope and that should be all. From the threads I saw, most of them make a singleton though traditional javascript new function(){} followed by making a pseudo constructor. Well I just think an object literal is enough enough: var singleton = { dothis: function(){}, dothat: function(){} } right? Or anybody got better insights? [update] : Again my point is why don't people just use a simpler way to make singletons in javascript as I showed in the second snippet, if there's an absolute reason please tell me. I'm usually afraid of this kind of situation that I simplify things to much :D

  Read the article

• Boost singleton trouble

  - by Ockonal

  Hi guys, I have some class which uses boost singleton. It calls some function from own c++ library. This library is written in make file as dependence. Now I have another singleton class and it should call first singleton class. After this code I got linkers error about undefined references for functions which are used in first singleton. When I remove calling first singleton class from second the errors remove. Maybe there is something wrong?

  Read the article

• How do I write a J2EE/EJB Singleton?

  - by Bears will eat you

  A day ago my application was one EAR, containing one WAR, one EJB JAR, and a couple of utility JAR files. I had a POJO singleton class in one of those utility files, it worked, and all was well with the world: EAR |--- WAR |--- EJB JAR |--- Util 1 JAR |--- Util 2 JAR |--- etc. Then I created a second WAR and found out (the hard way) that each WAR has its own ClassLoader, so each WAR sees a different singleton, and things break down from there. This is not so good. EAR |--- WAR 1 |--- WAR 2 |--- EJB JAR |--- Util 1 JAR |--- Util 2 JAR |--- etc. So, I'm looking for a way to create a Java singleton object that will work across WARs (across ClassLoaders?). The @Singleton EJB annotation seemed pretty promising until I found that JBoss 5.1 doesn't seem to support that annotation (which was added as part of EJB 3.1). Did I miss something - can I use @Singleton with JBoss 5.1? Upgrading to JBoss AS 6 is not an option right now. Alternately, I'd be just as happy to not have to use EJB to implement my singleton. What else can I do to solve this problem? Basically, I need a semi-application-wide* hook into a whole bunch of other objects, like various cached data, and app config info. As a last resort, I've already considered merging my two WARs into one, but that would be pretty hellish. *Meaning: available basically anywhere above a certain layer; for now, mostly in my WARs - the View and Controller (in a loose sense).

  Read the article

• Jboss 6 Cluster Singleton Clustered

  - by DanC

  I am trying to set up a Jboss 6 in a clustered environment, and use it to host clustered stateful singleton EJBs. So far we succesfully installed a Singleton EJB within the cluster, where different entrypoints to our application (through a website deployed on each node) point to a single environment on which the EJB is hosted (thus mantaining the state of static variables). We achieved this using the following configuration: Bean interface: @Remote public interface IUniverse { ... } Bean implementation: @Clustered @Stateful public class Universe implements IUniverse { private static Vector<String> messages = new Vector<String>(); ... } jboss-beans.xml configuration: <deployment xmlns="urn:jboss:bean-deployer:2.0"> <!-- This bean is an example of a clustered singleton --> <bean name="Universe" class="Universe"> </bean> <bean name="UniverseController" class="org.jboss.ha.singleton.HASingletonController"> <property name="HAPartition"><inject bean="HAPartition"/></property> <property name="target"><inject bean="Universe"/></property> <property name="targetStartMethod">startSingleton</property> <property name="targetStopMethod">stopSingleton</property> </bean> </deployment> The main problem for this implementation is that, after the master node (the one that contains the state of the singleton EJB) shuts down gracefuly, the Singleton's state is lost and reset to default. Please note that everything was constructed following the JBoss 5 Clustering documents, as no JBoss 6 documents were found on this subject. Any information on how to solve this problem or where to find JBoss 6 documention on clustering is appreciated.

  Read the article

• ngGrid reusable filter AngularJS

  - by wootscootinboogie

  I have a business requirement that I filter a boolean value in my ngGrid. The filter has three states: only true, only false and both. Filtering like this seems to be a common enough use case that I should refactor that functionality out of my code for re use (possibly in a directive/filter?). I'd like to know how I can go about pulling out the customFilter function in my controller and make it so that I can pass the filter a property name on which to filter, and a value for selectedFilterOption. The code currently works, but I feel like this is a good chance to get better at angular :). So how can I pull out my filtering used here and make it a reusable piece of functionality? app.controller('DocumentController',function($scope,DocumentService) { $scope.filterOptions = { filterText: '', useExternalFilter: false }; $scope.totalServerItems =0; $scope.pagingOptions ={ pageSizes: [5,10,100], pageSize: 5, currentPage: 1 } //filter! $scope.dropdownOptions = [{ name: 'Show all' },{ name: 'Show active' },{ name: 'Show trash' }]; //default choice for filtering is 'show active' $scope.selectedFilterOption = $scope.dropdownOptions[1]; //three stage bool filter $scope.customFilter = function(data){ var tempData = []; angular.forEach(data,function(item){ if($scope.selectedFilterOption.name === 'Show all'){ tempData.push(item); } else if($scope.selectedFilterOption.name ==='Show active' && !item.markedForDelete){ tempData.push(item); } else if($scope.selectedFilterOption.name ==='Show trash' && item.markedForDelete){ tempData.push(item); } }); return tempData; } //grabbing data $scope.getPagedDataAsync = function(pageSize, page, filterValue, searchText){ var data; if(searchText){ var ft = searchText.toLowerCase(); DocumentService.get('filterableData.json').success(function(largeLoad){ //filter the data when searching data = $scope.customFilter(largeLoad).filter(function(item){ return JSON.stringify(item).toLowerCase().indexOf(ft) != -1; }) $scope.setPagingData($scope.customFilter(data),page,pageSize); }) } else{ DocumentService.get('filterableData.json').success(function(largeLoad){ var testLargeLoad = $scope.customFilter(largeLoad); //filter the data on initial page load when no search text has been entered $scope.setPagingData(testLargeLoad,page,pageSize); }) } }; //paging $scope.setPagingData = function(data, page, pageSize){ var pagedData = data.slice((page -1) * pageSize, page * pageSize); //filter the data for paging $scope.myData = $scope.customFilter(pagedData); $scope.myData = pagedData; $scope.totalServerItems = data.length; if(!$scope.$$phase){ $scope.$apply(); } } //watch for filter option change, set the data property of gridOptions to the newly filtered data $scope.$watch('selectedFilterOption',function(){ var data = $scope.customFilter($scope.myData); $scope.myData = data; $scope.getPagedDataAsync($scope.pagingOptions.pageSize, $scope.pagingOptions.currentPage); $scope.setPagingData($scope.myData,$scope.pagingOptions.currentPage,$scope.pagingOptions.pageSize); }) $scope.$watch('pagingOptions',function(newVal, oldVal){ if(newVal !== oldVal && newVal.currentPage !== oldVal.currentPage){ $scope.getPagedDataAsync($scope.pagingOptions.pageSize,$scope.pagingOptions.currentPage,$scope.filterOptions.filterText); } },true) $scope.message ="This is a message"; $scope.gridOptions = { data: 'myData', enablePaging: true, showFooter:true, totalServerItems: 'totalServerItems', pagingOptions: $scope.pagingOptions, filterOptions: $scope.filterOptions, showFilter: true, enableCellEdit: true, showColumnMenu: true, enableColumnReordering: true, enablePinning: true, showGroupPanel: true, groupsCollapsedByDefault: true, enableColumnResize: true } //get the data on page load $scope.getPagedDataAsync($scope.pagingOptions.pageSize, $scope.pagingOptions.currentPage); }); HTML

  Read the article

• What is required for a scope in an injection framework?

  - by johncarl

  Working with libraries like Seam, Guice and Spring I have become accustomed to dealing with variables within a scope. These libraries give you a handful of scopes and allow you to define your own. This is a very handy pattern for dealing with variable lifecycles and dependency injection. I have been trying to identify where scoping is the proper solution, or where another solution is more appropriate (context variable, singleton, etc). I have found that if the scope lifecycle is not well defined it is very difficult and often failure prone to manage injections in this way. I have searched on this topic but have found little discussion on the pattern. Is there some good articles discussing where to use scoping and what are required/suggested prerequisites for scoping? I interested in both reference discussion or your view on what is required or suggested for a proper scope implementation. Keep in mind that I am referring to scoping as a general idea, this includes things like globally scoped singletons, request or session scoped web variable, conversation scopes, and others. Edit: Some simple background on custom scopes: Google Guice custom scope Some definitions relevant to above: “scoping” - A set of requirements that define what objects get injected at what time. A simple example of this is Thread scope, based on a ThreadLocal. This scope would inject a variable based on what thread instantiated the class. Here's an example of this: “context variable” - A repository passed from one object to another holding relevant variables. Much like scoping this is a more brute force way of accessing variables based on the calling code. Example: methodOne(Context context){ methodTwo(context); } methodTwo(Context context){ ... //same context as method one, if called from method one } “globally scoped singleton” - Following the singleton pattern, there is one object per application instance. This applies to scopes because there is a basic lifecycle to this object: there is only one of these objects instantiated. Here's an example of a JSR330 Singleton scoped object: @Singleton public void SingletonExample{ ... } usage: public class One { @Inject SingeltonExample example1; } public class Two { @Inject SingeltonExample example2; } After instantiation: one.example1 == two.example2 //true;

  Read the article

• Singleton pattern in web applications

  - by ryudice

  I'm using a singleton pattern for the datacontext in my web application so that I dont have to instantiate it every time, however I'm not sure how web applications work, does IIS open a thread for every user connected? if so, what would happend if my singleton is not thread safe? Also, is it OK to use a singleton pattern for the datacontext? Thanks.

  Read the article

• Examples of IOC/DI over Singleton

  - by Amitd

  Hi, Just started learning/reading about DI and IOC frameworks. Also I read many articles on SO and internet that say that one should prefer DI/IOC over singleton. Can anyone give/link examples of exactly how DI/IOC eliminates/solves the various issues regarding the Singleton pattern? (hopefully code and explanation for better understanding) Also given a system has already implemented Singleton pattern, how to refactor/implement DI/IOC for the same? (any examples for the same?) (Language/Framework no bars..C# would be helpful) Thanks

  Read the article

• Thread safe lazy contruction of a singleton in C++

  - by pauldoo

  Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before any code is executed (ie, even before static constructors are executed - their values may already be "initialized" in the program image)? If so - perhaps this can be exploited to implement a singleton mutex - which can in turn be used to guard the creation of the real singleton..) Excellent, it seems that I have a couple of good answers now (shame I can't mark 2 or 3 as being the answer). There appears to be two broad solutions: Use static initialisation (as opposed to dynamic initialisation) of a POD static varible, and implementing my own mutex with that using the builtin atomic instructions. This was the type of solution I was hinting at in my question, and I believe I knew already. Use some other library function like pthread_once or boost::call_once. These I certainly didn't know about - and am very grateful for the answers posted.

  Read the article

• Singleton Pattern for C#

  - by cam

  I need to store a bunch of variables that need to be accessed globally and I'm wondering if a singleton pattern would be applicable. From the examples I've seen, a singleton pattern is just a static class that can't be inherited. But the examples I've seen are overly complex for my needs. What would be the very simplest singleton class? Couldn't I just make a static, sealed class with some variables inside?

  Read the article

• How to create a true singleton in java?

  - by rjoshi

  I am facing a problem with my singleton when used across multiple class loaders. E.g Singleton accessed by multiple EJBs. Is there any way to create a singleton which has only one instance across all class loader? I am looking for pure java solution either using custom class loader or some other way.

  Read the article

• Javascript 'class' and singleton problems

  - by Kucebe

  I have a singleton object that use another object (not singleton), to require some info to server: var singleton = (function(){ /*_private properties*/ var myRequestManager = new RequestManager(params, //callbacks function(){ previewRender(response); }, function(){ previewError(); } ); /*_public methods*/ return{ /*make a request*/ previewRequest: function(request){ myRequestManager.require(request); //err:myRequestManager.require is not a func }, previewRender: function(response){ //do something }, previewError: function(){ //manage error } }; }()); This is the 'class' that make the request to the server function RequestManager(params, success, error){ //create an ajax manager this.param = params; this._success = success; //callbacks this._error = error; } RequestManager.prototype = { require: function(text){ //make an ajax request }, otherFunc: function(){ //do other things } } The problem is that i can't call myRequestManager.require from inside singleton object. Firebug consolle says: "myRequestManager.require is not a function", but i don't understand where the problem is. Is there a better solution for implement this situation?

  Read the article

• How to instantiate a Singleton multiple times?

  - by Sebi

  I need a singleton in my code. I implemented it in Java and it works well. The reason I did it, is to ensure that in a mulitple environment, there is only one instance of this class. But now I want to test my Singleton object locally with a Unit test. For this reason I need to simulate another instance of this Singleton (the object that would be from another device). So is there a possiblity to instantiate a Singleton a second time for testing purpose or do I have to mock it? I'm not sure, but I think it could be possible by using a different class loader?

  Read the article

• What are the downsides of implementing a singleton with Java's enum?

  - by irreputable

  Traditionally, a singleton is usually implemented as public class Foo1 { private static final Foo1 INSTANCE = new Foo1(); public static Foo1 getInstance(){ return INSTANCE; } private Foo1(){} public void doo(){ ... } } With Java's enum, we can implement a singleton as public enum Foo2 { INSTANCE; public void doo(){ ... } } As awesome as the 2nd version is, are there any downsides to it? (I gave it some thoughts and I'll answer my own question; hopefully you have better answers)

  Read the article

• should singleton be life-time available or should it be destroyable?

  - by Manoj R

  Should the singleton be designed so that it can be created and destroyed at any time in program or should it be created so that it is available in life-time of program. Which one is best practice? What are the advantages and disadvantages of both? EDIT :- As per the link shared by Mat, the singleton should be static. But then what are the disadvantages of making it destroyable? One advantage is it memory can be saved when it is not useful.

  Read the article

• iPhone noob - setting NSMutableDictionary entry inside Singleton?

  - by codemonkey

  Yet another iPhone/Objective-C noob question. I'm using a singleton to store app state information. I'm including the singleton in a Utilities class that holds it (and eventually other stuff). This utilities class is in turn included and used from various view controllers, etc. The utilities class is set up like this: // Utilities.h #import <Foundation/Foundation.h> @interface Utilities : NSObject { } + (id)GetAppState; - (id)GetAppDelegate; @end // Utilities.m #import "Utilities.h" #import "CHAPPAppDelegate.h" #import "AppState.h" @implementation Utilities CHAPPAppDelegate* GetAppDelegate() { return (CHAPPAppDelegate *)[UIApplication sharedApplication].delegate; } AppState* GetAppState() { return [GetAppDelegate() appState]; } @end ... and the AppState singleton looks like this: // AppState.h #import <Foundation/Foundation.h> @interface AppState : NSObject { NSMutableDictionary *challenge; NSString *challengeID; } @property (nonatomic, retain) NSMutableDictionary *challenge; @property (nonatomic, retain) NSString *challengeID; + (id)appState; @end // AppState.m #import "AppState.h" static AppState *neoAppState = nil; @implementation AppState @synthesize challengeID; @synthesize challenge; # pragma mark Singleton methods + (id)appState { @synchronized(self) { if (neoAppState == nil) [[self alloc] init]; } return neoAppState; } + (id)allocWithZone:(NSZone *)zone { @synchronized(self) { if (neoAppState == nil) { neoAppState = [super allocWithZone:zone]; return neoAppState; } } return nil; } - (id)copyWithZone:(NSZone *)zone { return self; } - (id)retain { return self; } - (unsigned)retainCount { return UINT_MAX; //denotes an object that cannot be released } - (void)release { // never release } - (id)init { if (self = [super init]) { challengeID = [[NSString alloc] initWithString:@"0"]; challenge = [NSMutableDictionary dictionary]; } return self; } - (void)dealloc { // should never be called, but just here for clarity [super dealloc]; } @end ... then, from a view controller I'm able to set the singleton's "challengeID" property like this: [GetAppState() setValue:@"wassup" forKey:@"challengeID"]; ... but when I try to set one of the "challenge" dictionary entry values like this: [[GetAppState() challenge] setObject:@"wassup" forKey:@"wassup"]; ... it fails giving me an "unrecognized selector sent..." error. I'm probably doing something really obviously dumb? Any insights/suggestions will be appreciated.

  Read the article

• ipv6 : why ndp resolves to global scope address?

  - by Julien

  I'm facing a strange ipv6 behavior and I don't know how to solve it because I'm not familiar with ipv6. Maybe this behavior is normal. I hope that you will help me. ( I'm running under debian 6.0.9 with a custom kernel 3.2.58 ) machine A is "2a00:7d30:edf6:100::1" wants to ping machine B, which is "2a00:7d30:edf6:100::10". Both are on the same segment. machine A asks for the address of machine B and I don't understand why machine B gives its global scope address instead of the local scope one ? 10:59:02.082785 IP6 2a00:7d30:edf6:100::1 ff02::1:ff00:10: ICMP6, neighbor solicitation, who has 2a00:7d30:edf6:100::10, length 32 10:59:02.082821 IP6 2a00:7d30:edf6:100::10 2a00:7d30:edf6:100::1: ICMP6, neighbor advertisement, tgt is 2a00:7d30:edf6:100::10, length 32 after that machine A pings the global scope address of machine B and it works fine : 10:59:02.082927 IP6 2a00:7d30:edf6:100::1 2a00:7d30:edf6:100::10: ICMP6, echo request, seq 1, length 64 10:59:02.082960 IP6 2a00:7d30:edf6:100::10 2a00:7d30:edf6:100::1: ICMP6, echo reply, seq 1, length 64 Thank you for you help best regards Julien

  Read the article

• Is Structuremap singleton thread safe?

  - by Ben

  Hi, Currently I have the following class: public class PluginManager { private static bool s_initialized; private static object s_lock = new object(); public static void Initialize() { if (!s_initialized) { lock (s_lock) { if (!s_initialized) { // initialize s_initialized = true; } } } } } The important thing here is that Initialize() should only be executed once whilst the application is running. I thought that I would refactor this into a singleton class since this would be more thread safe?: public sealed class PluginService { static PluginService() { } private static PluginService _instance = new PluginService(); public static PluginService Instance { get { return _instance; } } private bool s_initialized; public void Initialize() { if (!s_initialized) { // initialize s_initialized = true; } } } Question one, is it still necessary to have the lock here (I have removed it) since we will only ever be working on the same instance? Finally, I want to use DI and structure map to initialize my servcices so I have refactored as below: public interface IPluginService { void Initialize(); } public class NewPluginService : IPluginService { private bool s_initialized; public void Initialize() { if (!s_initialized) { // initialize s_initialized = true; } } } And in my registry: ForRequestedType<IPluginService>() .TheDefaultIsConcreteType<NewPluginService>().AsSingletons(); This works as expected (singleton returning true in the following code): var instance1 = ObjectFactory.GetInstance<IPluginService>(); var instance2 = ObjectFactory.GetInstance<IPluginService>(); bool singleton = (instance1 == instance2); So my next question, is the structure map solution as thread safe as the singleton class (second example). The only downside is that this would still allow NewPluginService to be instantiated directly (if not using structure map). Many thanks, Ben

  Read the article

• Thread implemented as a Singleton

  - by rocknroll

  Hi all, I have a commercial application made with C,C++/Qt on Linux platform. The app collects data from different sensors and displays them on GUI. Each of the protocol for interfacing with sensors is implemented using singleton pattern and threads from Qt QThreads class. All the protocols except one work fine. Each protocol's run function for thread has following structure: void <ProtocolClassName>::run() { while(!mStop) //check whether screen is closed or not { mutex.lock() while(!waitcondition.wait(&mutex,5)) { if(mStop) return; } //Code for receiving and processing incoming data mutex.unlock(); } //end while } Hierarchy of GUI. 1.Login screen. 2. Screen of action. When a user logs in from login screen, we enter the action screen where all data is displayed and all the thread's for different sensors start. They wait on mStop variable in idle time and when data arrives they jump to receiving and processing data. Incoming data for the problem protocol is 117 bytes. In the main GUI threads there are timers which when timeout, grab the running instance of protocol using <ProtocolName>::instance() function Check the update variable of singleton class if its true and display the data. When the data display is done they reset the update variable in singleton class to false. The problematic protocol has the update time of 1 sec, which is also the frame rate of protocol. When I comment out the display function it runs fine. But when display is activated the application hangs consistently after 6-7 hours. I have asked this question on many forums but haven't received any worthwhile suggestions. I Hope that here I will get some help. Also, I have read a lot of literature on Singleton, multithreading, and found that people always discourage the use of singletons especially in C++. But in my application I can think of no other design for implementation. Thanks in advance A Hapless programmer

  Read the article

• Can the Singleton be replaced by Factory?

  - by lostiniceland

  Hello Everyone There are already quite some posts about the Singleton-Pattern around, but I would like to start another one on this topic since I would like to know if the Factory-Pattern would be the right approach to remove this "anti-pattern". In the past I used the singleton quite a lot, also did my fellow collegues since it is so easy to use. For example, the Eclipse IDE or better its workbench-model makes heavy usage of singletons as well. It was due to some posts about E4 (the next big Eclipse version) that made me start to rethink the singleton. The bottom line was that due to this singletons the dependecies in Eclipse 3.x are tightly coupled. Lets assume I want to get rid of all singletons completely and instead use factories. My thoughts were as follows: hide complexity less coupling I have control over how many instances are created (just store the reference I a private field of the factory) mock the factory for testing (with Dependency Injection) when it is behind an interface In some cases the factories can make more than one singleton obsolete (depending on business logic/component composition) Does this make sense? If not, please give good reasons for why you think so. An alternative solution is also appreciated. Thanks Marc

  Read the article

• Trouble implementing Singleton pattern in Tomcat web application due to Class Loader

  - by jwegan

  I'm trying to implement a Singleton in Tomcat 6.24 on Linux with x86_64 OpenJDK 1.6. My application is just a bunch of JSPs and some static content and the JSPs make calls to my Java code. Currently the web.xml just looks like this: <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"> <description> App Name </description> <display-name>App Name</display-name> <!-- The Usual Welcome File List --> <welcome-file-list> <welcome-file>pages/index.jsp</welcome-file> </welcome-file-list> </web-app> Before when I was trying to load my Singleton it was getting instantiated twice since the class was getting loaded by two different class loaders (I'm not sure why) and each loader would create an instance of the singleton which is not acceptable for my application. I finally figured out if I exported my code as a jar and put it in $CATALINA_HOME/lib then there was only one instance, but this is not an elegant solution. I've been googling for hours, but I haven't come up with anything yet. I'm wondering if there is some other solution. Currently I'm not precompling my JSPs, could this be part of the problem? Could I write a servlet to ensure the singleton is created? If so how do I do that?

  Read the article

• Singleton issue causing a buffer overrun

  - by Rudiger

  Hi everyone, Ive created a singleton to store 2 arrays: @interface Globals : NSObject { NSMutableArray *items; NSMutableArray *extras; } + (Globals *)sharedInstance; @property (nonatomic, assign) NSMutableArray *items; @property (nonatomic, assign) NSMutableArray *extras; @end @implementation Globals @synthesize items, extras; + (Globals *)sharedInstance { static Globals *myInstance = nil; @synchronized(self) { if(!myInstance) { myInstance = [[Globals alloc] init]; } } return myInstance; } -(void)dealloc { [items release]; [extras release]; [super dealloc]; } @end When I set the Arrays in the singleton from the App delegate and then output them to NSLog it displays what is expected. But when I call it from a view controller further into the App it displays the first entry fine, some of the second entry and then garbage which is i assume a buffer overrun, sometimes it also crashes. I set the singleton array in the appDelegate like so: Globals *sharedInstance = [Globals sharedInstance]; [sharedInstance setItems:items]; and retrieve it: [[[sharedInstance items] objectAtIndex:indexPath.row] objectForKey:@"name"]; cell.description.text = [[[sharedInstance items] objectAtIndex:indexPath.row] objectForKey:@"description"]; Name works fine in both cells if there is 2, description works in the first case, never in the second case. Is it because the arrays in my singleton aren't static? If so why is it outputting the first entry fine? Cheers for any help.

  Read the article

• Singleton pattern in C++

  - by skydoor

  I have a question about the singleton pattern. I saw two cases concerning the static member in the singleton class. First it is an object, like this class CMySingleton { public: static CMySingleton& Instance() { static CMySingleton singleton; return singleton; } // Other non-static member functions private: CMySingleton() {} // Private constructor ~CMySingleton() {} CMySingleton(const CMySingleton&); // Prevent copy-construction CMySingleton& operator=(const CMySingleton&); // Prevent assignment }; One is an pointer, like this class GlobalClass { int m_value; static GlobalClass *s_instance; GlobalClass(int v = 0) { m_value = v; } public: int get_value() { return m_value; } void set_value(int v) { m_value = v; } static GlobalClass *instance() { if (!s_instance) s_instance = new GlobalClass; return s_instance; } }; What's the difference between the two cases? Which one is correct?

  Read the article

• please help me Assignment has more non-singleton rhs dimensions than non-singleton

  - by ENG RAED

  I have the following error in my code Assignment has more non-singleton rhs dimensions than non-singleton This is the code: string =['d:\face\face\ffw' int2str(r) '_' int2str(Sel(nSelRow,t)) '.bmp']; A = imread(string); B = im2double(A); Train_Dat(:,:,s)=B;

  Read the article

• Is it OK to use dynamic typing to reduce the amount of variables in scope?

  - by missingno

  Often, when I am initializing something I have to use a temporary variable, for example: file_str = "path/to/file" file_file = open(file) or regexp_parts = ['foo', 'bar'] regexp = new RegExp( regexp_parts.join('|') ) However, I like to reduce the scope my variables to the smallest scope possible so there is less places where they can be (mis-)used. For example, I try to use for(var i ...) in C++ so the loop variable is confined to the loop body. In these initialization cases, if I am using a dynamic language, I am then often tempted to reuse the same variable in order to prevent the initial (and now useless) value from being used latter in the function. file = "path/to/file" file = open(file) regexp = ['...', '...'] regexp = new RegExp( regexp.join('|') ) The idea is that by reducing the number of variables in scope I reduce the chances to misuse them. However this sometimes makes the variable names look a little weird, as in the first example, where "file" refers to a "filename". I think perhaps this would be a non issue if I could use non-nested scopes begin scope1 filename = ... begin scope2 file = open(filename) end scope1 //use file here //can't use filename on accident end scope2 but I can't think of any programming language that supports this. What rules of thumb should I use in this situation? When is it best to reuse the variable? When is it best to create an extra variable? What other ways do we solve this scope problem?

  Read the article

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >