Accessing <objc/runtime.h> from Cycript

Question

I wan't to be able to use associated objects and ISA swizzle, but I can't figure out how to import objc/runtime.h for use with Cycript. I have tried in both the console and in .js files but no luck.

Ideally I'd like to figure out how to include frameworks as well.

Answer 1

It seems like a subset of runtime.h is included by default in the Cycript environment. For example, class_copyMethodList and objc_getClass work without any added effort.

var count = new new Type(@encode(int));
var methods = class_copyMethodList(objc_getClass("NSObject"), count);

However objc_setAssociatedObject is not referenced:

objc_getAssociatedObject(someVar, "asdf")
#ReferenceError: Can't find variable: objc_getAssociatedObject

After a lot of searching, I realized the answer was right under my nose. limneos's weak_classdump uses the runtime to do it's dump and Cycript's tutorial shows how to grab C functions.

The solution I ended up with is this:

function setAssociatedObject(someObject, someValue, constVoidPointer) {
    SetAssociatedObject = @encode(void(id, const void*, id, unsigned long))(dlsym(RTLD_DEFAULT, "objc_setAssociatedObject"))
    SetAssociatedObject(someObject, constVoidPointer, someValue, 1)
}

function getAssociatedObject(someObject, constVoidPointer) {
    GetAssociatedObject = @encode(id(id, const void*))(dlsym(RTLD_DEFAULT, "objc_getAssociatedObject"))
    return GetAssociatedObject(someObject, constVoidPointer)
}

It is used like this:

# create void pointer (probably should be a global variable for later retrieval)
voidPtr = new new Type(@encode(const void))

someVar = [[NSObject alloc] init]
setAssociatedObject(someVar, @[@"hello", @"world"], voidPtr)
getAssociatedObject(someVar, voidPtr)
# spits out @["Hello", "World"]