把元组转换成proupists [英] Convert tuples to proplists

问题描述

如何从MongoDB转换元组

How can I convert tuple from MongoDB

{'_id',<<"vasya">>,password,<<"12ghd">>,age,undefined}

[{'_id',<<"vasya">>},{password,<<"12ghd">>},{age,undefined}]

推荐答案

假设你想基本上将元组的两个连续元素组合在一起，这不是太难了。您可以使用 element\2 从元组中拉元素。而 tuple_size\1 获取元组的大小。以下是几种处理方法：

Assuming you want to basically combine the two consecutive elements of the tuple together, this isn't too hard. You can use element\2 to pull elements from tuples. And tuple_size\1 to get the size of the tuple. Here's a couple of ways to handle this:

1> Tup = {'_id',<<"vasya">>,password,<<"12ghd">>,age,undefined}.
{'_id',<<"vasya">>,password,<<"12ghd">>,age,undefined}
2> Size = tuple_size(Tup).            
6

您可以使用列表解析：

3> [{element(X, Tup), element(X+1, Tup)} || X <- lists:seq(1, Size, 2)].
[{'_id',<<"vasya">>},{password,<<"12ghd">>},{age,undefined}]

或者你可以压缩它：

4> lists:zip([element(X, Tup) || X <- lists:seq(1, Size, 2)], [element(X, Tup) || X <- lists:seq(2, Size, 2)]).
[{'_id',<<"vasya">>},{password,<<"12ghd">>},{age,undefined}]

您可以通过执行拉出元素的功能来清理该zip。

You can clean up that zip by making a function to handle pulling elements out.

slice(Tuple, Start, Stop, Step) ->
    [element(N, Tuple) || N <- lists:seq(Start, Stop, Step)].

然后调用此函数：

5> lists:zip(slice(Tup, 1, Size, 2), Slice(Tup, 2, Size, 2)).
[{'_id',<<"vasya">>},{password,<<"12ghd">>},{age,undefined}]

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