Deciding which kind you want
When you design your application, you need to decide how you
will use the functions you will define:
-
If a function is general purpose and applies throughout an
application, make it a global function. -
If a function applies only to a particular kind of object,
make it an object-level function. You can still call the function
from anywhere in the application, but the function acts only on a
particular object type.For example, suppose you want a function that returns the
contents of a SingleLineEdit control in one window to another
window. Make it a window-level function, defined in the window
containing the SingleLineEdit control. Then, anywhere in your
application that you need this value, call the window-level
function.
Multiple objects can have functions with the same
name
Two or more objects can have functions with the same name that
do different things. In object-oriented terms, this is called
polymorphism. For example, each window type can have its own
Initialize function that performs processing unique to that window
type. There is never any ambiguity about which function is being
called, because you always specify the object’s name when you call
an object-level function.
Object-level functions can also be overloaded—two or more
functions can have the same name but different argument lists.
Global functions cannot be overloaded.