How do I enforce the user create a object via operator new only?

[Xie Yubo]

Hello every,
I have a question, could you help me?
How do I enforce the user create a object via operator new only?

For example, there is a class C:

class C
{
.....
}

Then the user can only create a C object with:
C* p = new C;
and
C c;
is forbided.

Are there some ways to implement it?

Thanks!

[Ian Collins]

Xie Yubo wrote:

Hello every,
I have a question, could you help me?
How do I enforce the user create a object via operator new only?

For example, there is a class C:

class C
{
.....
}

Then the user can only create a C object with:
C* p = new C;
and
C c;
is forbided.

Are there some ways to implement it?

Make the constructor private and private a friend function to return an
instance of the class.

class X
{
X() {}
friend X* makeX() { return new X; }
};

--
Ian Collins.

[Jerry Coffin]

In article <11************ *********@h3g20 00cwc.googlegro ups.com>,
xi*****@gmail.c om says...

Hello every,
I have a question, could you help me?
How do I enforce the user create a object via operator new only?

[ ... ]

FAQ, 16.21

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Xie Yubo]

On Jan 29, 7:27 am, Ian Collins <[e-mail] mwrote:

Xie Yubo wrote:

Hello every,
I have a question, could you help me?
How do I enforce the user create a object via operator new only?

For example, there is a class C:

class C
{
.....
}

Then the user can only create a C object with:
C* p = new C;
and
C c;
is forbided.

Are there some ways to implement it?Make the constructor private and private a friend function to return an

instance of the class.

class X
{
X() {}
friend X* makeX() { return new X; }

};--
Ian Collins.

But in this way, the user only use X* p = makeX(); not X* p = new X;

[Xie Yubo]

On Jan 29, 7:33 am, Jerry Coffin <jcof...@taeus. comwrote:

In article <1170026540.624 521.97...@h3g20 00cwc.googlegro ups.com>,
xiey...@gmail.c om says...

Hello every,
I have a question, could you help me?
How do I enforce the user create a object via operator new only?[ ... ]

FAQ, 16.21

--
Later,
Jerry.

The universe is a figment of its own imagination.

I have read it. But in that way, the user only use Fred* p =
Fred::create, not Fred* p = new Fred;

[Jerry Coffin]

In article <11************ **********@k78g 2000cwa.googleg roups.com>,
xi*****@gmail.c om says...

[ ... ]

I have read it. But in that way, the user only use Fred* p =
Fred::create, not Fred* p = new Fred;

That's right. What you asked for isn't possible, and that's as close as
you can get.

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Xie Yubo]

On Jan 29, 7:51 am, Jerry Coffin <jcof...@taeus. comwrote:

In article <1170028023.228 345.169...@k78g 2000cwa.googleg roups.com>,
xiey...@gmail.c om says...

[ ... ]

I have read it. But in that way, the user only use Fred* p =
Fred::create, not Fred* p = new Fred;That's right. What you asked for isn't possible, and that's as close as

you can get.

--
Later,
Jerry.

The universe is a figment of its own imagination.

Is it impossible? Ok, I see. Thanks every one!

[Chris]

Xie Yubo wrote:

On Jan 29, 7:33 am, Jerry Coffin <jcof...@taeus. comwrote:

>In article <1170026540.624 521.97...@h3g20 00cwc.googlegro ups.com>,
xiey...@gmail. com says...

Hello every,
I have a question, could you help me?
How do I enforce the user create a object via operator new only?[ ... ]

FAQ, 16.21

--
Later,
Jerry.

The universe is a figment of its own imagination.

I have read it. But in that way, the user only use Fred* p =
Fred::create, not Fred* p = new Fred;

Yes Xie that's right. This will ensure that Fred is dynamically created via
the new operator. So, since Fred::create() calls "new Fred;" then the user
is effectively calling new Fred.

--
Chris

[Grizlyk]

Xie Yubo wrote:

Then the user can only create a C object with:
C* p = new C;
and
C c;
is forbided.

class A
{
~A(){}

public:
int i;
static void destroy(A*);
};

void A::destroy(A* p){delete p;}

int main()
{

A a; //error
A *p=new A; //ok

delete p; //error
A::destroy(p); //ok
}

Probably you can overload "new" and "delete" operators for your class also.

--
Maksim A Polyanin

[Xie Yubo]

On Jan 29, 5:32 pm, "Grizlyk" <grizl...@yande x.ruwrote:

Xie Yubo wrote:

Then the user can only create a C object with:
C* p = new C;
and
C c;
is forbided.

class A
{
~A(){}

public:
int i;
static void destroy(A*);

};

void A::destroy(A* p){delete p;}

int main()
{

A a; //error
A *p=new A; //ok

delete p; //error
A::destroy(p); //ok

}

Probably you can overload "new" and "delete" operators for your class also.

--
Maksim A Polyanin

Wonderful! Thank you very much!