global | 易学教程

Global vs function vs static class method

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Let's say you have a object that is unique, and it's used by all other classes and functions ...something like $application . How would you access this object in your functions? using a global variable in each of you functions: global $application; $application->doStuff(); creating a function, like application() that instantiates the object into a static variable and returns it; then use this function everywhere you need to access the object: application()->doStuff(); create a singleton thing, like a static method inside the object class which returns the only instance, and use this method to

Use of static variables and functions in global scope

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问题 Is there a use for flagging a variable as static , when it lies in the global scope of a .cpp file, not in a function? Can you use the static keyword for functions as well? If yes, what is their use? 回答1: In this case, keyword static means the function or variable can only be used by code in the same cpp file. The associated symbol will not be exported and won't be usable by other modules. This is good practice to avoid name clashing in big software when you know your global functions or

Global Variable - database connection?

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I am trying to connect to a database (MySQLi) just once, but am having problems doing so. How do I make a connection global for the entire script? There are multiple files (index.php, /classes/config.class.php, /classes/admin.class.php, etc). I've tried the following: In: config.class.php public static $config = array(); public static $sql; function __construct() { // database db::$config['host'] = 'localhost'; db::$config['user'] = '_'; db::$config['pass'] = '_'; db::$config['db'] = '_'; // connect db::$sql = new mysqli(db::$config['host'], db::$config['user'], db::$config['pass'], db::

Global exception handling in C++

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Can i implement global exception handling in C++? My requirement is try...catch block is not used in a piece of code then there should be a global exception handler which will handle all uncaught exception. Can i achieve it, please give your valuable suggestion : ) I always wrap the outer-most function in a try-catch like this: int main() { try { // start your program/function Program program; program.Run(); } catch (std::exception& ex) { std::cerr << ex.what() << std::endl; } catch (...) { std::cerr << "Caught unknown exception." << std::endl; } } This will catch everything. Good exception

Global Exception Handling in Google App Engine

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问题 Instead of encapsulating my entire code in a try{} except{} block, is there someway of catching exceptions globally? Basically I am looking for a way to have a global exception handler which will handle all unhandled exceptions in the my python application written for google app engine 回答1: If you're using the webapp framework, you should already be defining a subclass of RequestHandler that serves as a base class, with all your app's handlers extending that. You can simply override handle

AspectJ - Creating a global Logger field using an Inter-Type Declaration

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问题 I'd like to create an Inter-Type declaration that declares a (static final) Logger instance inside each class. The constructor should be passed the enclosing class Klazz.class value: @Aspect public class LoggerAspect { public interface Logger { } public static class LoggerImpl implements Logger { private static final Logger logger = new Logger(thisJoinPoint.getTarget().getClass()/*.getName()*/); } @DeclareParents(value="com.my.api..*",defaultImpl=LoggerImpl.class) private Logger

When to use global variables in Swift

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问题 I'm learning Swift and iOS app development and I was wondering in which cases (if there are some) I should use global variables and constants in an iOS app. Global variables are variables that are defined outside of any function, method, closure, or type context. Local variables are variables that are defined within a function, method, or closure context. Using global variables usually seems inelegant and not advisable (it is in fact not recommended by most guides and tutorials) and to pass

Does using global variables impact performance in MATLAB?

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问题 As I understand, MATLAB cannot use pass by reference when sending arguments to other functions. I am doing audio processing, and I frequently have to pass waveforms as arguments into functions, and because MATLAB uses pass by value for these arguments, it really eats up a lot of RAM when I do this. I was considering using global variables as a method to pass my waveforms into functions, but everywhere I read there seems to be a general opinion that this is a bad idea, for organization of code

Share variables between functions in PHP without using globals

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问题 I have a class for interacting with a memcache server. I have different functions for inserting, deleting and retrieving data. Originally each function made a call to memcache_connect() , however that was unnecessary, e.g.: mc->insert() mc->get() mc->delete() would make three memcache connections. I worked around this by creating a construct for the class: function __construct() { $this->mem = memcache_connect( ... ); } and then using $this->mem wherever the resource was needed, so each of

Share variables between functions in PHP without using globals

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I have a class for interacting with a memcache server. I have different functions for inserting, deleting and retrieving data. Originally each function made a call to memcache_connect() , however that was unnecessary, e.g.: mc->insert() mc->get() mc->delete() would make three memcache connections. I worked around this by creating a construct for the class: function __construct() { $this->mem = memcache_connect( ... ); } and then using $this->mem wherever the resource was needed, so each of the three functions use the same memcache_connect resource. This is alright, however if I call the class