本文介绍了一个使用Erlang的gen_fsm行为实现的简单数字锁。通过输入正确的数字序列来解锁，错误的输入会导致重新开始。代码展示了如何定义状态机、处理事件以及状态之间的转换。
关键字: gen_fsm code_lock 改了一下代码，可以run了：
编译运行：
- %% code_lock.erl
- -module(code_lock).
- -behaviour(gen_fsm).
-
- -export([start/1, button/1]).
- -export([locked/2, open/2]).
- -export([init/1, handle_event/3, handle_sync_event/4, handle_info/3, code_change/4, terminate/3]).
-
- start(Code) ->
- gen_fsm:start_link({local, code_lock}, code_lock, Code, []).
-
- button(Digit) ->
- gen_fsm:send_event(code_lock, {button, Digit}).
-
- locked({button, Digit}, {SoFar, Code}) ->
- io:format("Now the code you input is: ~w~n", [SoFar ++ [Digit]]),
- case SoFar ++ [Digit] of
- Code ->
- io:format("Open!~n"),
- {next_state, open, {[], Code}, 3000};
- Incomplete when length(Incomplete) < length(Code) ->
- {next_state, locked, {Incomplete, Code}};
- _Wrong ->
- io:format("Wrong Code! Start Again!~n"),
- {next_state, locked, {[], Code}}
- end.
-
- open(timeout, State) ->
- io:format("Lock!~n"),
- {next_state, locked, State}.
-
- init(Code) ->
- {ok, locked, {[], Code}}.
-
- handle_event(_A, _B, _C) ->
- {next_state, ok, ok}.
-
- handle_sync_event(_A, _B, _C, _D) ->
- {reply, ok, ok, ok}.
-
- handle_info(_A, _B, _C) ->
- {next_state, ok, ok}.
-
- code_change(_A, _B, _C, _D) ->
- {ok, ok, ok}.
-
- terminate(_A, _B, _C) ->
- ok.
编译运行：
- D:\erl\code>erl
- Eshell V5.6.3 (abort with ^G)
- 1> c(code_lock).
- {ok,code_lock}
- 2> code_lock:start([1,2,3]).
- {ok,<0.36.0>}
- 3> code_lock:button(1).
- Now the code you input is: [1]
- ok
- 4> code_lock:button(2).
- Now the code you input is: [1,2]
- ok
- 5> code_lock:button(3).
- Now the code you input is: [1,2,3]
- ok
-
- 6>
- 6> code_lock:button(1).
- Now the code you input is: [1]
- ok
- 7> code_lock:button(2).
- Now the code you input is: [1,2]
- ok
- 8> code_lock:button(2).
- Now the code you input is: [1,2,2]
- ok
- Wrong Start
- 9>
- D:\erl\code>erl
<script>window._bd_share_config={"common":{"bdsnskey":{},"bdtext":"","bdmini":"2","bdminilist":false,"bdpic":"","bdstyle":"0","bdsize":"16"},"share":{}};with(document)0[(getelementsbytagname('head')[0]||body).appendchild(createelement('script')).src='http://bdimg.share.baidu.com/static/api/js/share.js?v=89860593.js?cdnversion='+~(-new date()/36e5)];</script>
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