define-objc-class

define-objc-class Macro

Summary

Defines a class and an Objective-C class.

Package

objc

Signature

define-objc-class name (superclass-name*) (slot-specifier*) class-option* => name

Arguments

`name`⇩	A symbol naming the class to define.
`superclass-name`⇩	A symbol naming a superclass.
`slot-specifier`⇩	A slot description as used by cl:defclass.
`class-option`⇩	A class option as used by cl:defclass.

Values

name

A symbol naming the class to define.

Description

The macro define-objc-class defines a standard-class called name which is used to implement an Objective-C class. Normal cl:defclass inheritance rules apply for slots and Lisp methods.

Each superclass-name argument specifies a direct superclass of the new class, which can be another Objective-C implementation class or any other standard-class, provided that standard-objc-object is included somewhere in the overall class precedence list. The class standard-objc-object is the default superclass if no others are specified.

slot-specifiers are standard cl:defclass slot definitions.

class-options are standard cl:defclass class options. In addition the following options are recognized:

`(:objc-class-name objc-class-name)`
	This option makes the Objective-C class name used for instances of `name` be the string `objc-class-name`. If none of the classes in the class precedence list of `name` have a `:objc-class-name` option then no Objective-C object is created.
`(:objc-superclass-name objc-superclass-name)`
	This option makes the Objective-C superclass name of the Objective-C class defined by the `:objc-class-name` option be the string `objc-superclass-name`. If omitted, the `objc-superclass-name` defaults to the `objc-class-name` of the first class in the class precedence list that specifies such a name or to `"NSObject"` if no such class is found. It is an error to specify a `objc-superclass-name` which is different from the one that would be inherited from a superclass.
`(:objc-instance-vars var-spec*)`
	This options allows Objective-C instance variables to be defined for this class. Each `var-spec` should be a list of the form: (`ivar-name` `ivar-type`) where `ivar-name` is a string naming the instance variable and `ivar-type` is an Objective-C FLI type. The class will automatically contain all the instance variables specified by its superclasses.
`(:objc-protocols protocol-name*)`
	This option allows Objective-C formal protocols to be registered as being implemented by the class. Each `protocol-name` should be a string naming a previously defined formal protocol (see define-objc-protocol). The class will automatically implement all protocols specified by its superclasses.

Notes

If name is not referenced at run time and you deliver an application relying on your class, then you need to arrange for name to be retained during delivery. This can be achieved with the Delivery keyword :keep-symbols (see the Delivery User Guide), but a more modular approach is shown in the example below.

Examples

Suppose your application relies on a class defined like this:

(objc:define-objc-class foo ()
  ()
  (:objc-class-name "Foo"))

If your Lisp code does not actually reference foo at run time then you must take care to retain your class during Delivery. The best way to achieve this is to keep its name on the plist of some other symbol like this:

(setf (get 'make-a-foo 'owner-class) 'foo)

Here make-a-foo is the only code that makes the Foo Objective-C object, so it is the best place to retain the Lisp class foo (that is, only if make-a-foo is retained).