On 1/24/06, David A. Greene <greened@obbligato.org> wrote:
David A. Greene wrote:
I'm having some trouble with BLL and Boost.Function in this simple testcase:
I worked around the problem using Boost.Function:
int main(void) { Test tester; int value = 10;
boost::function<void (int)> bound = boost::lambda::bind(&Test::foo, &tester, boost::lambda::_1); Caller<boost::function<void (void)> > printer(boost::lambda::bind(bound, value)); //Caller<boost::function<void (void)> > printer(boost::lambda::bind(boost::lambda::bind(&Test::foo, &tester, boost::lambda::_1), value));
printer.bar();
return(0); }
I have a couple of questions and another problem, however.
I had to pass "&tester" to the first bind expression because g++ complained about passing "tester" as "const Test &." Is passing by reference supposed to work?
Only if you use a reference wrapper - i.e. you can use boost::ref(tester) or boost::lambda::var(tester) rather than &tester
Also, this workaround gets rid of the error but is the original code supposed to work as written or did I do something incorrectly?
Finally, the new problem, closer to the actual code I'm working with:
#include <boost/lambda/bind.hpp> #include <boost/function.hpp> #include <boost/shared_ptr.hpp>
#include <iostream>
class Test { public: void foo(int a) { std::cout << "a is " << a << std::endl; }; };
template<typename Function> class Caller { private: Function func;
public: Caller(Function f) : func(f) {};
void bar(void) { func(); }; };
int main(void) { boost::shared_ptr<Test> tester(new Test); int value = 10;
boost::function<void (int)> bound = boost::lambda::bind(&Test::foo, tester, boost::lambda::_1); Caller<boost::function<void (void)> > printer(boost::lambda::bind(bound, value));
printer.bar();
return(0); }
If you're using a shared_ptr, you'll either need to use tester.get() directly to get a Test* to pass into the bind expression bind(&Test::foo, tester.get(), value) or something like bind(&Test::foo, bind(boost::shared_ptr<Test>::get, tester), value) to delay the call to tester.get() until invocation of printer.bar(). Stuart Dootson