How To Call D Code from Objective C?

[Jacob Carlborg via Digitalmars-d]

On 2015-12-11 09:20, Mike McKee wrote:

> I found a way to call C from in Objective C. The big trick is to rename
> a .m file to a .mm file.

.mm means Objective-C++. That is, combining C++ and Objective-C in the 
same file. Objective-C can call C functions directly with no problems. A 
global function in a .m file is a C function. NSLog, for example is a 
regular C function.

> So, I think there's probably a way for me to
> link a compiled C dylib into Objective C and then load its .h header
> file so that Objective C can call those C functions.
>
> I'll be using GCC to statically combine the D's .o code in with the C code.
>
> So, I'm thinking the process is like this:
>
> 1. Create a D function d_test() that takes a string input, concatenates
> on "-response", and returns the result. Compile as dtest.o with "dmd -c
> dtest.d".
>
> 2. Create a C function c_test() that takes a string input, calls
> d_test() and passes it the string, and then returns the response from
> d_test() out of c_test() as a string result. Compile as ctest.dylib with
> "gcc -dynamiclib -o ctest.dylib ctest.c dtest.o -L/usr/local/lib
> -lphobos2 -lpthread -lm".

This step is not necessary. You can call the D function directly without 
needing a wrapper.

> 3. In Xcode IDE, add this ctest.dylib linked library. Then, create a
> ctest.h for the function declaration.
>
> 4. In Objective C, import ctest.h in my main.mm file and then call with
> something like NSLog("RESULT=%s",c_test("request")); That should create
> a debugger line that reads: RESULT=request-response.
>
> The problem is that I don't know the entire way that I should create
> dtest.d and ctest.c.
>


-- 
/Jacob Carlborg