gistfile1.txt

# This module gives low-level access to the Objective-C runtime, 
# allowing classes to be created.
# Copyright 2014, Martin Percossi.
#

type
    ObjectId* = object      # represents id in Objective-C.
    ClassRepr* = object     # represents Class in Objective-C.
    Selector* = object      # represents SEL in Objective-C.
    MethodRepr* = object    # represents Method in Objective-C.
    MethodImpl* = proc (self: ptr[ObjectId], sel: ptr[Selector]) {.cdecl.}

proc objc_getClass*(className: cstring): ptr[ClassRepr]
    {.importc, dynlib: "objc".}

proc objc_allocateClassPair*(superclassObj: ptr[ClassRepr], name: cstring, extraBytes: int64): ptr[ClassRepr]
    {.importc, dynlib: "objc".}

proc objc_registerClassPair*(cls: ptr[ClassRepr])
    {.importc, dynlib: "objc".}

proc sel_registerName*(str: cstring): ptr[Selector]
    {.importc, dynlib: "objc".}

proc class_addMethod*(cls: ptr[ClassRepr], name: ptr[Selector], imp: MethodImpl, types: cstring): bool
    {.importc, dynlib: "objc".}

proc class_getInstanceMethod*(cls: ptr[ClassRepr], selector: ptr[Selector]): ptr[MethodImpl]
    {.importc, dynlib: "objc".}

proc objc_msgSend*(self: ptr[ObjectId], op: ptr[Selector])
    {.importc, dynlib: "objc", varargs.}

proc class_createInstance*(cls: ptr[ClassRepr], extraBytes: int64): ptr[ObjectId]
    {.importc, dynlib: "objc", varargs.}

proc myImpl(self: ptr[ObjectId], sel: ptr[Selector]) {.cdecl, exportc.} =
    echo("Hello, Objective-C!")

proc test() =
    var 
        nsobjClass = objc_getClass("NSObject")
        cls = objc_allocateClassPair(nsobjClass, "NSFoo", 0)
        sel = sel_registerName("foo")
        ok = class_addMethod(cls, sel, myImpl, "v@:")

    objc_registerClassPair(cls)
    var obj = class_createInstance(cls, 0)
    objc_msgSend(obj, sel)

when isMainModule:
    test()

gistfile2.txt

# This is a higher level interface to Objective-C,
# allowing to create classes and methods at runtime.

import objcapi as llobjc

proc myImpl(self: ptr[llobjc.ObjectId], sel: ptr[llobjc.Selector]) {.cdecl, exportc.} =
    echo("Hello, Objective-C!")

proc test() =
    var 
        nsobjClass = llobjc.objc_getClass("NSObject")
        cls = llobjc.objc_allocateClassPair(nsobjClass, "NSFoo", 0)
        sel = llobjc.sel_registerName("foo")
        ok = llobjc.class_addMethod(cls, sel, myImpl, "v@:")

    llobjc.objc_registerClassPair(cls)
    var obj = llobjc.class_createInstance(cls, 0)
    llobjc.objc_msgSend(obj, sel)

when isMainModule:
    test()