class Egg {
Egg e;
int i;
Egg(int ii=0) : i(ii) {}
};
because you would end up with an endless definition (memory allocation) of Egg objects, thus int i.
Ok, so God Eckel proposes for a singleton:
Code:
class Egg {
static Egg e;
int i;
Egg(int ii=0) : i(ii) {}
};
Egg Egg::e(47);
Does the static qualifier prevent from the memory allocation for the endless series of int i? I am not quite sure because any new Egg object (thus, int i) is in an inner scope (e.e...), even static says that all Egg objects share the same static memory for that member. ???
I understand that making the constructor private prevents the class user from creating any object, leaving us only with the shared static data member, previously defined by the class creator. Right?
Thanks for reading
Moderator's Comments:
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Hi, i have a question about C++. Is it possible to declare a class with a member ot the same class? For example, a linked list or i want to convert this C code to C++ class (Elemento)
typedef struct elemento
{
char name;
char value;
List<struct elemento> ltElementos;
... (7 Replies)
Hi all!
I am trying to register a device in an existing device class, but I am
having trouble getting the pointer to an existing class.
I can create a class in a module, get the pointer to it and then use
it to register the device with:
*cl = class_create(THIS_MODULE, className);... (0 Replies)
I have the two class definition as follows.
class A { public: int a; };
class B : virtual public A{ };
The size of class A is shown as 4, and size of class B is shown as 16. Why is this effect ?. (2 Replies)
Hello All,
I am a learner in C++. I was testing my inheritance knowledge with following piece of code.
#include <iostream>
using namespace std;
class base
{
public :
void display()
{
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}
void display(int k)
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Discussion started by: milhan
3 Replies
LEARN ABOUT MOJAVE
moosex::singleton5.18
MooseX::Singleton(3) User Contributed Perl Documentation MooseX::Singleton(3)NAME
MooseX::Singleton - turn your Moose class into a singleton
VERSION
version 0.29
SYNOPSIS
package MyApp;
use MooseX::Singleton;
has env => (
is => 'rw',
isa => 'HashRef[Str]',
default => sub { \%ENV },
);
package main;
delete MyApp->env->{PATH};
my $instance = MyApp->instance;
my $same = MyApp->instance;
DESCRIPTION
A singleton is a class that has only one instance in an application. "MooseX::Singleton" lets you easily upgrade (or downgrade, as it
were) your Moose class to a singleton.
All you should need to do to transform your class is to change "use Moose" to "use MooseX::Singleton". This module uses metaclass roles to
do its magic, so it should cooperate with most other "MooseX" modules.
METHODS
A singleton class will have the following additional methods:
Singleton->instance
This returns the singleton instance for the given package. This method does not accept any arguments. If the instance does not yet exist,
it is created with its defaults values. This means that if your singleton requires arguments, calling "instance" will die if the object has
not already been initialized.
Singleton->initialize(%args)
This method can be called only once per class. It explicitly initializes the singleton object with the given arguments.
Singleton->_clear_instance
This clears the existing singleton instance for the class. Obviously, this is meant for use only inside the class itself.
Singleton->new
This method currently works like a hybrid of "initialize" and "instance". However, calling "new" directly will probably be deprecated in a
future release. Instead, call "initialize" or "instance" as appropriate.
BUGS
Please report any bugs or feature requests to "bug-moosex-singleton@rt.cpan.org", or through the web interface at <http://rt.cpan.org>. We
will be notified, and then you'll automatically be notified of progress on your bug as we make changes.
SOME CODE STOLEN FROM
Anders Nor Berle <debolaz@gmail.com>
AND PATCHES FROM
Ricardo SIGNES <rjbs@cpan.org>
AUTHOR
Shawn M Moore <sartak@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2011 by Shawn M Moore.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
perl v5.18.2 2011-12-08 MooseX::Singleton(3)
08-09-2012
static use for class inside the same class c++
