I have a parameter (in this case std::vector) that I need to pass to an async method (preferably by move) and to a callback lambda. Does the approach below guarantee that the lambda will be initialized first (implying vector being copied) so that I can move the vector to the async method?
Method(std::vector<std::string> vec)
{
AsyncMethod(std::move(vec), [vec]()
{
// act on vec
});
}
The order of evaluation of function parameter is unspecified, hence you can't rely on your assumption. A solution would be the following.
Method(std::vector<std::string> vec)
{
auto l = [vec]() { /* Act on vec... */ };
AsyncMethod(std::move(vec), l);
}
Depending on the signature of AsyncMethod, you might even want to pass the lambda as std::move(l). This would again be safe, as the vector has been copied into the closure beforehand.