Event callback function type

Member function type for callback functions to be registered with register_callback member function.

It is defined as a member function of ios_base as:

typedef void (*event_callback) (event ev, ios_base& obj, int index);

Therefore it is a function returning no value and having three parameters:

ev

The first parameter is an object of enum member type ios_base::event. When the callback function is called, this parameter is set to one of the three possible values to indicate what type of event triggered the function call.

obj

When the callback function is called, this parameter is a reference to the calling ios_base-derived object (*this).

index

When the callback function is called, this parameter is set to the same value used as the index argument when the function was registered with register_callback.

See also