(goops.info.gz) Instance Slots
Info Catalog
(goops.info.gz) Accessing Slots
(goops.info.gz) Class Slots
Instance Slots
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Any slot, regardless of its allocation, can be queried, referenced and
set using the following four primitive procedures.
- primitive procedure: slot-exists? obj slot-name
Return `#t' if OBJ has a slot with name SLOT-NAME, otherwise `#f'.
- primitive procedure: slot-bound? obj slot-name
Return `#t' if the slot named SLOT-NAME in OBJ has a value,
otherwise `#f'.
`slot-bound?' calls the generic function `slot-missing' if OBJ
does not have a slot called SLOT-NAME ( slot-missing
Handling Slot Access Errors.).
- primitive procedure: slot-ref obj slot-name
Return the value of the slot named SLOT-NAME in OBJ.
`slot-ref' calls the generic function `slot-missing' if OBJ does
not have a slot called SLOT-NAME ( slot-missing Handling
Slot Access Errors.).
`slot-ref' calls the generic function `slot-unbound' if the named
slot in OBJ does not have a value ( slot-unbound Handling
Slot Access Errors.).
- primitive procedure: slot-set! obj slot-name value
Set the value of the slot named SLOT-NAME in OBJ to VALUE.
`slot-set!' calls the generic function `slot-missing' if OBJ does
not have a slot called SLOT-NAME ( slot-missing Handling
Slot Access Errors.).
GOOPS stores information about slots in class metaobjects. Internally,
all of these procedures work by looking up the slot definition for the
slot named SLOT-NAME in the class metaobject for `(class-of OBJ)', and
then using the slot definition's "getter" and "setter" closures to get
and set the slot value.
The next four procedures differ from the previous ones in that they take
the class metaobject as an explicit argument, rather than assuming
`(class-of OBJ)'. Therefore they allow you to apply the "getter" and
"setter" closures of a slot definition in one class to an instance of a
different class.
[ *fixme* I have no idea why this is useful! Perhaps when a slot in
`(class-of OBJ)' shadows a slot with the same name in one of its
superclasses? There should be an enlightening example here. ]
- primitive procedure: slot-exists-using-class? class obj slot-name
Return `#t' if the class metaobject CLASS has a slot definition
for a slot with name SLOT-NAME, otherwise `#f'.
- primitive procedure: slot-bound-using-class? class obj slot-name
Return `#t' if applying `slot-ref-using-class' to the same
arguments would call the generic function `slot-unbound', otherwise
`#f'.
`slot-bound-using-class?' calls the generic function
`slot-missing' if CLASS does not have a slot definition for a slot
called SLOT-NAME ( slot-missing Handling Slot Access
Errors.).
- primitive procedure: slot-ref-using-class class obj slot-name
Apply the "getter" closure for the slot named SLOT-NAME in CLASS
to OBJ, and return its result.
`slot-ref-using-class' calls the generic function `slot-missing'
if CLASS does not have a slot definition for a slot called
SLOT-NAME ( slot-missing Handling Slot Access Errors.).
`slot-ref-using-class' calls the generic function `slot-unbound'
if the application of the "getter" closure to OBJ returns an
unbound value ( slot-unbound Handling Slot Access Errors.).
- primitive procedure: slot-set-using-class! class obj slot-name value
Apply the "setter" closure for the slot named SLOT-NAME in CLASS
to OBJ and VALUE.
`slot-set-using-class!' calls the generic function `slot-missing'
if CLASS does not have a slot definition for a slot called
SLOT-NAME ( slot-missing Handling Slot Access Errors.).
Info Catalog
(goops.info.gz) Accessing Slots
(goops.info.gz) Class Slots
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