Although you could maintain a C version of some variable along with a
separate Ruby version of that variable, and struggle to keep the two
in sync,
[A clear violation of the DRY--Don't
Repeat Yourself---principle described in our book The Pragmatic
Programmer .] it would be much better to
share a variable directly between Ruby and C.
You can share global
variables by creating a Ruby object on the C side and then binding
its address to a Ruby global variable. In this case, the $ prefix is
optional, but it helps clarify that this is a global variable.
VALUE hardware_list;
hardware_list = rb_ary_new();
rb_define_variable("$hardware", &hardware_list);
...
rb_ary_push(hardware_list, rb_str_new2("DVD"));
rb_ary_push(hardware_list, rb_str_new2("CDPlayer1"));
rb_ary_push(hardware_list, rb_str_new2("CDPlayer2"));
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The Ruby side can then access the C variable
hardware_list as
$hardware:
$hardware
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� |
["DVD", "CDPlayer1", "CDPlayer2"]
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You can also create
hooked
variables that will call a specified function when the variable is
accessed, and
virtual variables that only call the hooks---no
actual variable is involved. See the API section that begins
on page 189 for details.
If you create a Ruby object from C and store it in a C global
variable
without exporting it to Ruby, you must at least tell the
garbage collector about it, lest ye be reaped inadvertently:
VALUE obj;
obj = rb_ary_new();
rb_global_variable(obj);
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