A BList
object is a compact, ordered list of data pointers.
BList objects
can contain pointers to any type of data, including—and
especially—objects.
An item assigned to a
BList
is identified by an index to its position in
the list. Indices start at 0 and are neither arbitrary nor permanent. If,
for example, you insert an item into the middle of a list, the indices of
the items at the tail of the list are incremented (by one). Similarly,
removing an item decrements the indices of the following items.
A BList
stores its items as type void*, so it's necessary to cast an
item to the correct type when you retrieve it. For example, items
retrieved from a list of
BBitmap
objects must be cast as
BBitmap pointers:
BBitmap*theImage= (BBitmap*)myList->ItemAt(anIndex);
There's nothing to prevent you from adding a NULL
pointer to a BList.
However, functions that retrieve items from the list (such as
ItemAt())
return NULL when the requested item can't be found. Thus, you can't
distinguish between a valid NULL item and an invalid attempt to access an
item that isn't there.
