A class defined with define-objc-class has no methods associated with it by default, other than those inherited from the its ancestor classes. New methods can be defined (or overridden) by using the macros define-objc-method for instance methods and define-objc-class-method for class methods.
Note that the Lisp method definition form is separate from the class definition, unlike in Objective-C where it is embedded in the
@implementation
block. Also, there is no Lisp equivalent of the
@interface
block: the methods of an Objective-C class are just those whose defining forms have been evaluated.
When defining a method, various things must be specified:
For example, a method that would be implemented in an Objective-C class as follows:
@implementation MyObject
- (unsigned int)areaOfWidth:(unsigned int)width
height:(unsigned int)height
{
return width*height;
}
@end
could be defined in Lisp for instances of the
MyObject
class from Defining an Objective-C class using the form:
(define-objc-method ("areaOfWidth:height:" (:unsigned :int))
((self my-object)
(width (:unsigned :int))
(height (:unsigned :int)))
(* width height))
The variable
self
is bound to an object of type
my-object
and
width
and
height
is bound to unsigned integers. The area is returned to the caller as an unsigned integer.