Hi all;

I want to write a class as follows:

class Foo
{
public:
Foo();
~Foo()

void Start(void);

private:
boost::thread* ptr;
void Update(int x, int y);
};

void
Foo::Start(void)
{
ptr = new boost::thread( boost::bind( &Update, x, y) ); //
compiler complains here
}

All I want to do is creating a Foo object, initializing it and
creating a thread which is calling Update() member function after
calling Start() member function. However, compiler complains and says
that

"error: ISO C++ forbids taking the address of an unqualified or
parenthesized non-static member function to form a pointer to member
function."

It seems that creating a thread that calls a member function is
impossible, and called function must be static. However, I have to
call a member function as thread, since it performs some calculation
on object's attributes. How can I solve this problem? Any ,
suggestion will be appreciated.


Thanks
yatko

yatko wrote:

> I want to write a class as follows:

> class Foo
> {
> public:
> Foo();
> ~Foo()

> void Start(void);

> private:
> boost::thread* ptr;
> void Update(int x, int y);
> };

> void
> Foo::Start(void)
> {
> ptr = new boost::thread( boost::bind( &Update, x, y) ); //
> compiler complains here
> }

And what is boost::thread supposed to do with &Update? Update
is a non-static member function, and can only be called on an
object. Of type Foo. The only object you're giving
boost::thread is the result of boost::bind.

And of course, you can't take the address of a member function
like that anyway; the syntax would be &Foo::Update (even in a
member function of Foo).

You need is something like:

boost::bind( &Foo::Update, this, x, y ) ;

> All I want to do is creating a Foo object, initializing it
> and creating a thread which is calling Update() member
> function after calling Start() member function. However,
> compiler complains and says that

> "error: ISO C++ forbids taking the address of an unqualified
> or parenthesized non-static member function to form a pointer
> to member function."

Well, that's the obvious syntax error mentionned above. Once
you've resolved that, you still have to tell bind what object to
use when calling the member function.

> It seems that creating a thread that calls a member function
> is impossible, and called function must be static.

No, but you have to tell bind (and thus boost::thread) what
object to use. And you have to use the correct syntax for a
pointer to member.

(I modified your code so that start() took two arguments, x and
y, and with the suggested corrections, it worked for me.)

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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