Re: returning a data member's address - how?

James Kanze <>
Sun, 12 Apr 2009 03:53:43 -0700 (PDT)
On Apr 11, 9:44 pm, Arne Mertz <> wrote:

Greg Shaw schrieb:

I see what you mean about perhaps breaking encapsulation
here. Maybe I'm designing this the wrong way. I'll tell you
my reasons - the code on my system which deals with IP
clients/servers is written in C. The function available to
me on my system to connect from a socket accepts as

1. a pointer to the start of the IPaddress
2. an IPaddress+port length

The IPaddress and Port variables (not the actual names I
used, but you get the idea) are held in a C struct called
Socket (for argument's sake).

I don't have the expertise or access rights to change the
function or write my own in C++, so I'm stuck with that. I
did, however, fancy at least writing my own Socket class to
hold the data members. I'm a relative newbie at this and
enjoy the practice. So anyway, I have the class written, and
it contains accessor methods to Get (but not set) the
address of the IPAddress member and the combined
IPAddress+port length. Feed them into the C function, and it
should work just as if I were using a C struct to hold the
data, is the theory (yet to be tested). However, I'm
wondering if the better course might be to just use the C
struct for the job at hand, and regard my class as a
learning exercise, if I'm breaking encapsulation by
providing the address of a data member. Ho hum.

If I understand you correctly, you wrapped the IPaddress, port
(and perhaps other data) in your Socket class. But to make a
connection to the corresponding socket, your code calls the
plain C function, giving it the pointer to your socket class'

If the class is called Socket, that makes sense. But there's
also a strong argument for having a NetworkAddress class,
containing an IPAddress and a PortAddress. (Well, maybe
defining a class for the latter is a bit overkill.) In such
cases, you do need some means of obtaining a pointer from
IPAddress which can be used to call connect.

James Kanze (GABI Software)
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