▼Objective-C FFI
On this page:
tell
tellv
import-class
define-objc-class
self
super-tell
get-ivar
set-ivar!
selector
Version: 4.2.1
  top← prev  up  next → 

3 Syntactic Forms

(tell result-type obj-expr method-id)
(tell result-type obj-expr arg ...)
 
result-type = 
  | #:type ctype-expr
     
arg = method-id expr
  | #:type ctype-expr method-id arg
Sends a message to the Objective-C object produced by obj-expr. When a type is omitted for either the result or an argument, the type is assumed to be _id, otherwise it must be specified as an FFI C type (see Type Constructors).

If a single method-id is provided with no arguments, then method-id must not end with :; otherwise, each method-id must end with :.

Examples:

  > (tell NSString alloc)

  #<cpointer:id>

  > (tell (tell NSString alloc)
          initWithUTF8String: #:type _string "Hello")

  #<cpointer:id>

(tellv obj-expr method-id)
(tellv obj-expr arg ...)
Like tell, but with a result type _void.

(import-class class-id ...)
Defines each class-id to the class (a value with FFI type _Class) that is registered with the string form of class-id. The registered class is obtained via objc_lookUpClass.

Example:

  > (import-class NSString)

(define-objc-class class-id superclass-expr
  [field-id ...]
  method)
 
method = (mode result-ctype-expr (method-id) body ...+)
  | (mode result-ctype-expr (arg ...+) body ...+)
     
mode = +
  | -
  | +a
  | -a
     
arg = method-id [ctype-expr arg-id]
Defines class-id as a new, registered Objective-C class (of FFI type _Class). The superclass-expr should produce an Objective-C class or #f for the superclass.

Each field-id is an instance field that holds a Scheme value and that is initialized to #f when the object is allocated. The field-ids can be referenced and set! directly when the method bodys. Outside the object, they can be referenced and set with get-ivar and set-ivar!.

Each method adds or overrides a method to the class (when mode is - or -a) to be called on instances, or it adds a method to the meta-class (when mode is + or +a) to be called on the class itself. All result and argument types must be declared using FFI C types (see Type Constructors). When mode is +a or -a, the method is called in atomic mode (see _cprocedure).

If a method is declared with a single method-id and no arguments, then method-id must not end with :. Otherwise, each method-id must end with :.

If the special method dealloc is declared for mode -, it must not call the superclass method, because a (super-tell dealloc) is added to the end of the method automatically. In addition, before (super-tell dealloc), space for each field-id within the instance is deallocated.

Example:

  > (define-objc-class MyView NSView
      [bm] ; <- one field
      (- _scheme (swapBitwmap: [_scheme new-bm])
         (begin0 bm (set! bm new-bm)))
      (- _void (drawRect: [_NSRect exposed-rect])
         (super-tell drawRect: exposed-rect)
         (draw-bitmap-region bm exposed-rect))
      (- _void (dealloc)
         (when bm (done-with-bm bm))))

self
When used within the body of a define-objc-class method, refers to the object whose method was called. This form cannot be used outside of a define-objc-class method.

(super-tell result-type method-id)
(super-tell result-type arg ...)
When used within the body of a define-objc-class method, calls a superclass method. The result-type and arg sub-forms have the same syntax as in tell. This form cannot be used outside of a define-objc-class method.

(get-ivar obj-expr field-id)
Extracts the Scheme value of a field in a class created with define-objc-class.

(set-ivar! obj-expr field-id value-expr)
Sets the Scheme value of a field in a class created with define-objc-class.

(selector method-id)
Returns a selector (of FFI type _SEL) for the string form of method-id.

Example:

  > (tellv button setAction: #:type _SEL (selector terminate:))

  top← prev  up  next →