Finish basic ui binding to ruby

include/binding/ruby.h

@@ -12,10 +12,20 @@ struct Block {
 
   Block() : proc(mrb_nil_value()) {}
 
+  void set_proc(mrb_value new_proc) {
+    if (!mrb_nil_p(proc))
+      mrb_gc_unregister(mrb, proc);
+    proc = new_proc;
+    if (!mrb_nil_p(proc))
+      mrb_gc_register(mrb, proc);
+  }
+
   Block(const Block &) = delete;
   Block &operator=(const Block &) = delete;
 
   mrb_value call(int argc = 0, mrb_value *argv = nullptr) const {
+    if (mrb_nil_p(proc))
+      return mrb_nil_value();
     return mrb_funcall(mrb, proc, "call", argc, argv);
   }
 
@@ -23,4 +33,10 @@ struct Block {
     mrb_gc_unregister(mrb, proc);
   }
 };
+
+inline void run_string(const char *code, size_t length) {
+  int ai = mrb_gc_arena_save(mrb);
+  mrb_load_nstring(mrb, code, length);
+  mrb_gc_arena_restore(mrb, ai);
+}
 }; // namespace Ruby