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V-man
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 Posted: Fri Mar 05, 2004 11:59 pm Post subject: about member variables that are static, and threads |
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I have a slight problem.
I have a class with it's own member variables and a member function.
I'm dealing with threads, so I made the variables and that mem
function static
class X
{
public:
static int value;
static void ThreadFuncToBeCalled();
};
void X::ThreadFuncToBeCalled()
{
.... running the thread .........
}
//there is more code of course, but this is the jist of it
the trouble is, since value has to be static, it is *shared* by all
the instances of X.
I want each instance of X to have it's own copy of value and at the
same time be static.
Or maybe there is a better solution you can recommend.
TIA
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Dhruv Matani
Guest
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| Posted: Sat Mar 06, 2004 10:09 am Post subject: Re: about member variables that are static, and threads |
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On Fri, 05 Mar 2004 18:59:27 -0500, V-man wrote:
| Quote: | I have a slight problem.
I have a class with it's own member variables and a member function.
I'm dealing with threads, so I made the variables and that mem
function static
class X
{
public:
static int value;
static void ThreadFuncToBeCalled();
};
void X::ThreadFuncToBeCalled()
{
.... running the thread .........
}
//there is more code of course, but this is the jist of it
the trouble is, since value has to be static, it is *shared* by all
the instances of X.
I want each instance of X to have it's own copy of value and at the
same time be static.
Or maybe there is a better solution you can recommend.
|
I actually did encounter this problem some time ago.
From my previous experience and the extra knowlegde that I have gained
because of a similar post on this group:
1. Ususlly a thread function returns a void* and accepts a void*.
2. Using this information, we can change all statics to non-statics.
3. Make the thread Proc accept a void* that is actually an X*.
4. Cast the void* to an X* inside the thread function, and use the members
like normal.
5. Would there would be 2 ways to get the above behaviour? I'm slightly
confused on this count:
a. One way seems natural which would be to make the data public, and let
anyone acces it.
b The 2nd method is slightly counter intuitive. I was thinking that we
could make the static member a friend of the class so that it may access
it's private parts, but since it is already a member, it already does have
those priviledges except that it may not access non-statics? So what is
the verdict of the gurus? Can the static member access the private
non-static members given a pointer to the class? Also I realized that
making a member function a friend of the class would again be
counter-intuitive.
--
Regards,
-Dhruv.
Proud to be a Vegetarian.
http://www.vegetarianstarterkit.com/
http://www.vegkids.com/vegkids/index.html
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Francis Glassborow
Guest
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| Posted: Sat Mar 06, 2004 3:14 pm Post subject: Re: about member variables that are static, and threads |
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In message <e1da64ba.0403050852.67931584 (AT) posting (DOT) google.com>, V-man
<j_carbone (AT) excite (DOT) com> writes
| Quote: | I have a slight problem.
I have a class with it's own member variables and a member function.
I'm dealing with threads, so I made the variables and that mem
function static
|
I do not understand the logic of that statement.
| Quote: |
class X
{
public:
static int value;
static void ThreadFuncToBeCalled();
};
void X::ThreadFuncToBeCalled()
{
.... running the thread .........
}
//there is more code of course, but this is the jist of it
the trouble is, since value has to be static, it is *shared* by all
the instances of X.
I want each instance of X to have it's own copy of value and at the
same time be static.
|
Please explain what you mean by that statement. Are you using the word
'static' in the sense of being done at compile time, or is it that you
need a free function rather than a member function. Let me assume the
latter, then:
class X {
int value;
friend void ThreadFuncToBeCalled(X&)
public:
// ctors etc.
};
void ThreadFuncToBeCalled(X& x_ref){
// whatever
}
Note that there is no way of have distinct values of X::value without
either implicitly (as a member function) or explicitly via a declared
parameter telling the function which version it is to use.
Actually, strictly speaking that is not true because I could use a
global variable to identify which one to use such as:
X * active_X(0);
but all this really requires much more knowledge of your design
objectives than you have so far provided.
--
Francis Glassborow ACCU
Author of 'You Can Do It!' see http://www.spellen.org/youcandoit
For project ideas and contributions: http://www.spellen.org/youcandoit/projects
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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