Now I'll show you an example of calling OCaml from Objective-C. Much of this code will have simplifications as its an example for getting you started. Also note that dealing at the C level and the OCaml runtime can be tricky and is not for beginners.
Here's the OCaml code first, assume it is named code.ml
1: let make_string () = 2: print_endline "Hello Word from OCaml"; 3: "Hello World " 4: 5: let () = 6: Callback.register "make_string" make_string
We're essentially telling the runtime to make this function available to grab as a handle, in this case it's a handle on a closure.
And now the Objective-C code, assume it is named main.c
1: #define CAML_NAME_SPACE
2:
3: #import <Foundation/Foundation.h>
4:
5: #include <caml/callback.h>
6: #include <caml/mlvalues.h>
7:
8: int main (int argc, char **argv)
9: {
10: caml_startup(argv);
11: caml_callback(*caml_named_value("make_string"), Val_unit);
12: NSLog(@"Now using objective-c code");
13: return 0;
14: }
Its important to call caml_startup before any OCaml callbacks. Then
we get a handle on the closure and call it with unit.
To compile this code you'll need the cross-compiler which was installed by following the directions on my opam-ios repo, the command you use is:
$ ocamloptrev -rev 8.3 -ccopt -ObjC -cclib '-framework Foundation' main.c code.ml -o F
The 8.3 is the iOS SDK you want to link against, again see the README on the github repo for opam-ios for more details.
The output we get, F is an arm executable, when we run it on the
iPhone we will get an output of:
$ some_iphone :~/ ./F Hello Word from OCaml 2016-01-23 22:44:04.889 F[1977:507] Now using objective-c code
Yay!