Game Development Reference
In-Depth Information
handler += [](void*, int data)
{ std::cout << “Callback: “ << data << std::endl; }
When the event is invoked by calling handler.Invoke(this, n); (where n is any int), the
lambda function will be called and we would see the output “Callback: n” in the standard
It's possible to use std::function in conjunction with std::bind , which allows us to create
functions for which certain arguments are already bound to some value to bind a function
object to a member function of an object.
using std::placeholders;
event_handler<wchar_t> inputEventHandler;
keyboard keyb;
auto onInputFunction =
std::bind(&keyboard::OnInput, &keyb, _1, _2);
inputEventHandler += onInputFunction;
In this example, we know that an event handler expects a callback function with the signa-
ture (void*, T), where T is defined by the template argument, these parameters are repres-
entedbytheplaceholder values_1,_2and std::bind returnsafunctionpointertothe OnIn-
put member function in the object keyb. This is one possible use of std::bind , however it
can also be used for argument reordering, binding to member data as well as functions and
of course, creating functions with bound arguments.
Static functions may also be provided as callbacks:
static void onEvent(void* sender, int d)
std::cout << “Callback: “ << data << std::endl;
event_hander<int> handler;
handler += onEvent;
In short, it's possible to bind any callable object to an event handler, which one you choose
will depend entirely on the game's code architecture or a particular feature.
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