singleton

问题 I was pointed last week about a piece of code like this: #include <pthread.h> namespace NSTest { class SingletonClass { public: static SingletonClass & getInstance() { static pthread_mutex_t mutex; pthread_mutex_lock(&mutex); if(singletonPtr==nullptr) { createInstence(); } return (*singletonPtr); pthread_mutex_unlock(&mutex); } private: static void createInstence() { static SingletonClass static_SingletonClass; singletonPtr=&static_SingletonClass; } static SingletonClass * singletonPtr; };

问题 I was pointed last week about a piece of code like this: #include <pthread.h> namespace NSTest { class SingletonClass { public: static SingletonClass & getInstance() { static pthread_mutex_t mutex; pthread_mutex_lock(&mutex); if(singletonPtr==nullptr) { createInstence(); } return (*singletonPtr); pthread_mutex_unlock(&mutex); } private: static void createInstence() { static SingletonClass static_SingletonClass; singletonPtr=&static_SingletonClass; } static SingletonClass * singletonPtr; };

问题 I've noticed that the keyword static in PHP is not that static at all. Lets say Elmo is my singleton: class Elmo { private static $instance; private function __construct() { echo 'Elmo says constructor\n'; } public static function getInstance() { if (!isset(self::$instance)) self::$instance = new Elmo(); return self::$instance; } public function boo() { echo 'Elmo says boo!\n'; } } And the following file is just a regular .php script. <?php Elmo::getInstance()->boo(); Elmo::getInstance()->boo

问题 I need to implement an async singleton, that creates a single instance of a class that requires asynchronous operations in order to pass arguments to the constructor. I have the following code: class AsyncComp { constructor(x, y) { this.x = x; this.y = y; } // A factory method for creating the async instance static async createAsyncInstance() { const info = await someAsyncFunction(); return new AsyncComp(info.x, info.y); } // The singleton method static getAsyncCompInstance() { if

问题 I need to implement an async singleton, that creates a single instance of a class that requires asynchronous operations in order to pass arguments to the constructor. I have the following code: class AsyncComp { constructor(x, y) { this.x = x; this.y = y; } // A factory method for creating the async instance static async createAsyncInstance() { const info = await someAsyncFunction(); return new AsyncComp(info.x, info.y); } // The singleton method static getAsyncCompInstance() { if

问题 I am working on a project where I have lots of classes referring to my GUI (mainly the panels but sometimes the frame itself). So I was thinking that instead of passing the frame as an argument to every constructor and create getters in each class, I would make a singleton instance of the JFrame so all the classes get access to it instead. Is this a good approach or will it just punish my laziness in some way? Edit: I'm not just lazy, I'm trying to think in models here: For example, let's say

问题 In a small Qt application, I have a NetworkAccessManager(NAM) wrapped in a singleton class. NAM object of this class is used by four independent form classes. Each form class fires a request to a separate php (and php takes at least 3 seconds with sleep(3)). Now there are two cases: Case I: When NAM, for each form, is connected to form's slot IN CONSTRUCTOR. In this case, when i send requests from all four forms simultaneously; all the responses are directed to just one form (the one that was

问题 In a small Qt application, I have a NetworkAccessManager(NAM) wrapped in a singleton class. NAM object of this class is used by four independent form classes. Each form class fires a request to a separate php (and php takes at least 3 seconds with sleep(3)). Now there are two cases: Case I: When NAM, for each form, is connected to form's slot IN CONSTRUCTOR. In this case, when i send requests from all four forms simultaneously; all the responses are directed to just one form (the one that was

问题 I am writing an iOS app with several (maybe 8) survey-style modules where the user will answer a series of questions (on Family Life, Health, etc.). Some modules have as many as 12 questions. Each question has its own nib and its own UIViewController. The answers will be written to a database, ideally, at the end of the module. Each module corresponds with one record in one table. There will only ever be one user, hence, one record. I want to leave the Core Data stack in the app delegate. I

问题 I am writing an iOS app with several (maybe 8) survey-style modules where the user will answer a series of questions (on Family Life, Health, etc.). Some modules have as many as 12 questions. Each question has its own nib and its own UIViewController. The answers will be written to a database, ideally, at the end of the module. Each module corresponds with one record in one table. There will only ever be one user, hence, one record. I want to leave the Core Data stack in the app delegate. I