Re: clarification on pointer use
Ruby Stevenson <ruby185@gmail.com> wrote:
So one is store a pointer to event; the other store a copy of the
event in a container.
what are the implications between the two choices? when would be the
proper use of one instead of the other?
Storing the Event objects by value is much safer (and depending on
its size, often more efficient) than storing pointers to dynamically
allocated Event objects.
However, storing them by value requires that Event objects can be
copied (which means that if Even contains any dynamically allocated
resources, those have to be handled properly in its copy constructor
and assignment operator). If Event contains only basic (non-pointer)
types and class objects (which themselves have working copy constructors)
as members then you don't need to do anything special about it, and it
will work just fine. However, as said, if Event contains dynamically
allocated resources (in most cases having a pointer as member is usually
an indication of this).
Also take into account that if Event is very large (eg. it could contain
things like large std::vectors as members) copying will be a heavy
operation.
Storing dynamically allocated Event objects is error-prone because it
requires you to delete them appropriately (or else you'll get a memory
leak). Usually, if this is required, it's better to use a smart pointer
instead of a raw pointer.
Storing them as pointers allows runtime polymorphism (which storing by
value does not allow). In other words, you could store in the vector
objects of type Event or any object derived from it. This is about the
only advantage of storing pointers instead of objects. (The other is,
as said, if the objects are very large and are heavy to copy.)