Terms 26: Restrict the number of objects that can be produced in a Class
Allow zero or an object
Zero, very simple, privatizes the constructor of the object. One, it is also very simple, Singleton mode. I also have blogs to discuss local static objects in front.
Construction status of different objects
There are three states of objects, (1) Objects (2) existing in derived class object (3) as a member object exists in a larger object. We usually do this, usually do this
Class A
{
Private:
A () {}
A (const a &) {}
PUBLIC:
Static a * Makea () {Return New A ();
Static A * Makea (Const A & a) {Return New A (A);
}
In order to avoid resource leakage, such objects can usually be placed in a smart pointer.
Allow objects to endocate
When more than one object, you can make a limit in Makea () if a number of times returns NULL or throws an exception.
Class A
{
Private:
A () {}
A (const a &) {}
~ A () {- NumObjects;
Static size_t numoBjects;
Static const size_t maxObjects;
PUBLIC:
Static a * Makea ()
{
IF (NumObjects> = maxObjects)
Return NULL;
Else
{
NumObjects;
Return new a ();
}
}
Static A * Makea (Const A & A)
{
IF (NumObjects> = maxObjects)
Return NULL;
Else
{
NumObjects;
Return new a (a);
}
}
}
SIZE_T A :: NumObjects = 0;
Const size_t a :: maxObjects = 10;
Base Class used to calculate the number of objects
Consider the following code:
Template
<
Class
Beingcounted
>
Class
Ccounted
{
public
:
Class
Toomanyojects
{};
Static
int
Objectcount
() {
Return
NumberObjects
}
protected
:
Ccounted
() {
init
();
Ccounted
(
Const
Ccounted
&
RHS
) {
init
();
Virtual
~
Ccounted
() {
NumberObjects
}
Private
:
Static
Const
int
MaxObjects
;
Static
int
NumberObjects
;
Void
init
()
{
IF
(
NumberObjects
> =
MaxObjects
)
Throw
Toomanyojects
();
NumberObjects
;
}
}
Template
<
Class
Beingcounted
>
int
Ccounted
<
Beingcounted
> ::
NumberObjects
= 0;
Template
<
Class
Beingcounted
>
Const
int
Ccounted
<
Beingcounted> ::
MaxObjects
= 10;
Class
PRINTER
:
Private
Ccounted
<
PRINTER
>
{
public
:
Static
PRINTER
*
Makeprinter
() {
Return
New
PRINTER
}
Static
PRINTER
*
Makeprinter
(
Const
PRINTER
&
RHS
) {
Return
New
PRINTER
(
RHS
}
Virtual
~
PRINTER
() {}
Using
Ccounted
<
PRINTER
> ::
Objectcount
;
Private
:
PRINTER
() {}
PRINTER
(
Const
PRINTER
&) {}
}
The following code, I tested in VC6, there is no problem. On the original basis, in the destructure, the decrease in the number of objects was added. This is based on future object reference counts.
