Erlang（四）顺序程序的错误处理

kailian 2015-05-10

内置函数显示生成错误

  • exit(Why)终止当前进程

  • throw(Why)抛出调用者可能要捕捉的异常

  • error(Why)崩溃性错误

try...catch捕捉异常

  1. try expression of
  2.     pattern when guard ->
  3.         body
  4. catch
  5.     pattern when guard ->
  6.         body
  7. after
  8.     body
  9. end

try...catch具有一个值

  1. fun() [when guard] ->
  2.     body
  3.     try ... end
  4. end
  8. -module(try_test).
  9. -compile(export_all).
  10. generate_exception(1) -> a;
  11. generate_exception(2) -> throw(a);
  12. generate_exception(3) -> exit(a);
  13. generate_exception(4) -> {'EXIT', a};
  14. generate_exception(5) -> error(a).
  15. demo1() ->
  16.     [catcher(I) || I <- [1,2,3,4,5]].
  18. catcher(N) ->
  19.     try generate_exception(N) of
  20.         Val -> {N, normal, Val}
  21.     catch
  22.         throw:X -> {N, caught, thrown, X};
  23.         exit:X  -> {N, caught, exited, X};
  24.         error:X -> {N, caught, error, X}
  25.     end.
  26. demo2() ->
  27.     [{I, (catch generate_exception(I))} || I <- [1,2,3,4,5]].
  29. demo3() ->
  30.     try generate_exception(5)
  31.     catch
  32.        error:X ->
  33.          {X, erlang:get_stacktrace()}
  34.     end.	    
  35. lookup(N) ->
  36.       case(N) of
  37.       1 -> {'EXIT', a};
  38.       2 -> exit(a)
  39.     end.

重点是任其崩溃,永远不要在函数被错误参数调用时返回一个值，而是要抛出一个错误，假定调用者会修复这个错误。

erlang9