An instance (or object) of a defined class can be created with
make takes one mandatory parameter, which is the
class of the instance to create, and a list of optional arguments that
will be used to initialize the slots of the new instance. For instance
the following form
(define c (make <my-complex>))
creates a new
<my-complex> object and binds it to the Scheme
Create and return a new instance of class class, initialized using initarg ....
In theory, initarg … can have any structure that is
understood by whatever methods get applied when the
generic function is applied to the newly allocated instance.
In practice, specialized
initialize methods would normally call
(next-method), and so eventually the standard GOOPS
initialize methods are applied. These methods expect
initargs to be a list with an even number of elements, where
even-numbered elements (counting from zero) are keywords and
odd-numbered elements are the corresponding values.
GOOPS processes initialization argument keywords automatically for slots
whose definition includes the
#:init-keyword option (see init-keyword). Other keyword value pairs can only be
processed by an
initialize method that is specialized for the new
instance’s class. Any unprocessed keyword value pairs are ignored.
make-instance is an alias for
The slots of the new complex number can be accessed using
slot-set! sets the value
of an object slot and
slot-ref retrieves it.
(slot-set! c 'r 10) (slot-set! c 'i 3) (slot-ref c 'r) ⇒ 10 (slot-ref c 'i) ⇒ 3
(oop goops describe) module provides a
function that is useful for seeing all the slots of an object; it prints
the slots and their values to standard output.
(describe c) -| #<<my-complex> 401d8638> is an instance of class <my-complex> Slots are: r = 10 i = 3