Question

我有像这样的列表 ItemListData = [[1,"ABC","DEF",30],[2,"AXN","FOO",23],[3,"BDE","FO1",21],..]我希望使用记录Item{ItemNo, Name, Description, quantity}形成记录列表。项目列表长度会有所不同。使用ItemListData创建新记录列表的最佳方法是什么。

Answer 1

@ graymalkin的答案涉及通过使用++二元运算符进行大量复制。人们应该更喜欢这里的列表理解：

make_records(Records) ->
    [#item{'#'=No, name=Name, descr=Descr, qty=Qty}
    || [No,Name,Descr,Qty] <- Records].

编辑：因此使用此功能:(在shell中）

1> rd(item, {'#', name, descr, qty}).
2> ItemListData = [[1,"ABC","DEF",30],[2,"AXN","FOO",23],[3,"BDE","FO1",21]].
3> some_module:make_records(ItemListData).

Answer 2

这样的事情会......

make_records([], Records) -> Records; make_records([[No,Name,Desc,Qty]|Xs], Records) -> make_records(Xs, Records ++ Item{itemNo = No, name = Name, desc = Desc, qty = Qty}).

Answer 3

你只需要这个：

rd(item, {num, name, descr, qty}).
L = [[1,"ABC","DEF",30],[2,"AXN","FOO",23],[3,"BDE","FO1",21]].
lists:map(fun([No, Name, Des, Qty]) -> #item{num = No, name=Name, descr=Des, qty=Qty} end, L).

Answer 4

只需使用list_to_tuple：

rd(item, {num, name, descr, qty}),    
Ls = [[1,"ABC","DEF",30],[2,"AXN","FOO",23],[3,"BDE","FO1",21]],
[list_to_tuple([item|L]) || L <- Ls].

如何使用erlang中的列表数据列表生成记录列表

4 个答案: