更新时间:2021-11-05 04:33:01
-module(mochiweb_request, [Socket, Method, RawPath, Version, Headers]).
-author('bob@mochimedia.com').
-include_lib("kernel/include/file.hrl").
-include("internal.hrl").
-define(QUIP, "Any of you quaids got a smint?").
-module(p,[Name,ID]).
-compile(export_all).
test() ->
{Name,ID}.
dump(Data) ->
Data.
-module(p2).
-compile(export_all).
test(Name,ID) ->
{Name,ID}.
dump(Data) ->
Data.
Eshell V5.9 (abort with ^G)
1> P=p:new(zen,23).
{p,zen,23}
2> P:test().
{zen,23}
3> P:dump(12).
12
4> p:dump(12).
** exception error: undefined function p:dump/1
%%复习一下Function cal
1> list_to_tuple([a,b,c]).
{a,b,c}
2> tuple_to_list({a,b,c}).
[a,b,c]
3>
4> F={lists,append}.
{lists,append}
5> F([1,2],[3,4]).
[1,2,3,4]
6> fun lists:append/2([a,b],[c,d]).
[a,b,c,d]
7>
上面的代码首先创建了p模块的实例,然后调用P:test().虽然并没有传入什么参数,还是可以看到Name,ID的输出;后面直接调用p:dump(12).的时候抛出了异常:undefined function p:dump/1 ;这就驱使我们查看p模块的module_info,果然如此,{dump,2}dump的参数是标记成两个!!!!
5> p:module_info().
[{exports,[{new,2},
{instance,2},
{test,1},
{dump,2}, %注意dump的参数是两个
{module_info,0},
{module_info,1}]},
{imports,[]},
{attributes,[{vsn,[214441158221151374600508513707091486952]},
{abstract,[true]}]},
{compile,[{options,[error_summary]},
{version,"4.8"},
{time,{2012,2,16,7,23,32}},
{source,"/ligaoren/src/p.erl"}]}]
6>
7> P2=p:new(zen,23).
{p,zen,23}
8> P2=:= P.
true
9> {p,zen,34}:test().
{zen,34}
11> p2:module_info().
[{exports,[{test,2},
{dump,1},
{module_info,0},
{module_info,1}]},
{imports,[]},
{attributes,[{vsn,[248741352456702936001456553656546909458]}]},
{compile,[{options,[error_summary]},
{version,"4.8"},
{time,{2012,2,16,7,26,8}},
{source,"/ligaoren/src/p2.erl"}]}]
module 'p2' ['dump'/1,
'module_info'/0,
'module_info'/1,
'test'/2]
attributes []
'test'/2 =
%% Line 10
fun (_cor1,_cor0) ->
%% Line 11
{_cor1,_cor0}
'dump'/1 =
%% Line 13
fun (_cor0) ->
_cor0
'module_info'/0 =
fun () ->
call 'erlang':'get_module_info'
('p2')
'module_info'/1 =
fun (_cor0) ->
call 'erlang':'get_module_info'
('p2', _cor0)
end
module 'p' ['dump'/2,
'instance'/2,
'module_info'/0,
'module_info'/1,
'new'/2,
'test'/1]
attributes ['abstract' =
['true']]
'new'/2 =
fun (_cor1,_cor0) ->
apply 'instance'/2
(_cor1, _cor0)
'instance'/2 =
fun (_cor1,_cor0) ->
{'p',_cor1,_cor0}
'test'/1 =
%% Line 11
fun (_cor0) ->
case _cor0 of
<THIS = {_cor2,Name,ID}> when 'true' ->
%% Line 12
{Name,ID}
( <_cor1> when 'true' ->
( primop 'match_fail'
({'function_clause',_cor1})
-| [{'function_name',{'test',1}}] )
-| ['compiler_generated'] )
end
'dump'/2 =
%% Line 15
fun (_cor1,_cor0) ->
case <_cor1,_cor0> of
<Data,THIS = {_cor4,Name,ID}> when 'true' ->
%% Line 16
Data
( <_cor3,_cor2> when 'true' ->
( primop 'match_fail'
({'function_clause',_cor3,_cor2})
-| [{'function_name',{'dump',2}}] )
-| ['compiler_generated'] )
end
'module_info'/0 =
fun () ->
call 'erlang':'get_module_info'
('p')
'module_info'/1 =
fun (_cor0) ->
call 'erlang':'get_module_info'
('p', _cor0)
end
-module(q,[Name]). -compile(export_all). dump()-> THIS. Erlang Shell中调用: 2> Q=q:new(zen). {q,zen} 3> Q:dump(). {q,zen}
我们上面已经判断出来实例的创建过程实际上就是构造了{module,State}的结构,来验证下:
'new'/2 =
fun (_cor1,_cor0) ->
apply 'instance'/2
(_cor1, _cor0)
'instance'/2 =
fun (_cor1,_cor0) ->
{'p',_cor1,_cor0} %%GOTCHA!!!!!
上面遗留的dump参数的问题至此也就昭然了,看代码实现:
'dump'/2 =
%% Line 15
fun (_cor1,_cor0) ->
case <_cor1,_cor0> of
<Data,THIS = {_cor4,Name,ID}> when 'true' ->
%% Line 16
Data
( <_cor3,_cor2> when 'true' ->
( primop 'match_fail'
({'function_clause',_cor3,_cor2})
-| [{'function_name',{'dump',2}}] )
-| ['compiler_generated'] )
end
也就是说答案是:最后一个参数是模块的实例,实验一下
6> p:dump(12,{p,zen,23}).
12
GOTCHA!!!