c++ - How do I decide if I should use a pointer or a regular variable? -

in c++ can declare field regular variable of type, instantiate in constructor, , use later:

private:    foo field; ...  a::a() {     // upd: instatiate field wrong ways (see comments)     field = fieldimpl(); } .... method(field);

or alternatively can use pointer:

private:    foo* field; ...  a::a() {     field = new fieldimpl(); }  a::~a() {     delete field; }  ... method(*field);

when declaring field, how decide if should use pointer or regular variable?

you might want use pointer if:

the referenced object can outlive parent.
because of size, want ensure referenced object on heap.
the pointer provided outside class.
null possible value.
the field can set dynamically different object.
the actual object type determined @ runtime. example, field might base-class pointer of number of subclasses.

you might want use smart pointer.

the last point above applies sample code. if field of type foo, , assign fieldimpl it, remains foo part of fieldimpl. referred slicing problem.

Babette