有没有更简单的方法来修改Erlang中subsubsub记录字段中的值?
因此,我有一个相当深的记录定义层次:有没有更简单的方法来修改Erlang中subsubsub记录字段中的值?,erlang,records,Erlang,Records,因此,我有一个相当深的记录定义层次: -record(cat, {name = '_', attitude = '_',}). -record(mat, {color = '_', fabric = '_'}). -record(packet, {cat = '_', mat = '_'}). -record(stamped_packet, {packet = '_',
-record(cat, {name = '_', attitude = '_',}).
-record(mat, {color = '_', fabric = '_'}).
-record(packet, {cat = '_', mat = '_'}).
-record(stamped_packet, {packet = '_', timestamp = '_'}).
-record(enchilada, {stamped_packet = '_', snarky_comment = ""}).
现在我有了一个玉米饼,我想做一个新的
除了其中一个子记录的值之外,与之类似。
这就是我一直在做的
update_attitude(Ench0, NewState)
when is_record(Ench0, enchilada)->
%% Pick the old one apart.
#enchilada{stamped_packet = SP0} = Ench0,
#stamped_packet{packet = PK0} = SP0,
#packet{cat = Tag0} = PK0,
%% Build up the new one.
Tude1 = Tude0#cat{attitude = NewState},
PK1 = PK0#packet{cat = Tude1},
SP1 = SP0#stamped_packet{packet = PK1},
%% Thank God that's over.
Ench0#enchilada{stamped_packet = SP1}.
仅仅想到这一点是痛苦的。有更好的方法吗?试试这个:
update_attitude(E = #enchilada{
stamped_packet = (SP = #stamped_packet{
packet = (P = #packet{
cat = C
})})}, NewState) ->
E#enchilada{
stamped_packet = SP#stamped_packet{
packet = P#packet{
cat = C#cat{
attitude = NewState
}}}}.
无论如何,结构不是Erlang最强大的部分。正如Hynek所建议的,您可以省略临时变量并执行以下操作:
update_attitude(E = #enchilada{stamped_packet = (P = #packet{cat=C})},
NewAttitude) ->
E#enchilada{stamped_packet = P#packet{cat = C#cat{attitude=NewAttitude}}}.
对同样的问题感到沮丧,然后写下,这将允许你写:
-compile({parse_transform, recless}).
update_attitude(Enchilada = #enchilada{}, Attitude) ->
Enchilada.stamped_packet.packet.cat.attitude = Attitude.