M-OSCAR

Q：有如下函數：

1> rd(test, {key, value}).
2> Arg = test.
3> record_info(fields, test).
[key, value]
4> record_info(fields, Arg).
* 1: illegal record info

Arg跟記錄名test系一樣的，為什么传入record_info里會提示错误呢？？

A：转Google Goups - [erlang-questions]上的一段解答：
record_info is not a proper function. It only exists during compilation, which means that it cannot take variable arguments:

record_info(fields, address) %% works
Rec = address,
record_info(fields, Rec) %% doesn't work!

Of course it only works if the address record is defined in that module. If you do want a function that uses record_info, try to use a macro instead.

定義成Macro就可以？馬上試試先：

-record(test, {key, value}).
-define(FIELDS(Record), record_info(fields, Record)).
....
?FIELDS(test).
> [key, value]

哇哇，果然OK哦～～