How can I operate std::async call on a member function?
Example:
class Person{
public:
void sum(int i){
cout << i << endl;
}
};
int main(int argc, char **argv) {
Person person;
async(&Person::sum,&person,4);
}
I want to call to sum async.
Person p;
call async to p.sum(xxx)
I didnt figure out if i can do it with std::async. Dont want to use boost. Looking for a one line async call way.
Something like this:
auto f = std::async(&Person::sum, &p, xxx);
or
auto f = std::async(std::launch::async, &Person::sum, &p, xxx);
where p is a Person instance and xxx is an int.
This simple demo works with GCC 4.6.3:
#include <future>
#include <iostream>
struct Foo
{
Foo() : data(0) {}
void sum(int i) { data +=i;}
int data;
};
int main()
{
Foo foo;
auto f = std::async(&Foo::sum, &foo, 42);
f.get();
std::cout << foo.data << "\n";
}
std::async(&Person::sum, &p, xxx)
std::async isn't properly implemented in your compiler.There are several ways, but I find it's most clear to use a lambda, like this:
int i=42;
Person p;
auto theasync=std::async(std::launch::async,[&p,i]{ return p.sum(i);});
This creates a std::future. For a complete example of this, I have a full example including a async-capable setup of mingw here:
http://scrupulousabstractions.tumblr.com/post/36441490955/eclipse-mingw-builds
You need to make sure that p is thread safe and that the &p reference is valid until the async is joined. (You can also hold p with a shared pointer, or in c++14, a unique_ptr or even move p into the lambda.)
