Erlang：JSON 列表到 JSON 列表

发布于 2024-09-26 07:36:32 字数 1006 浏览 7 评论 0原文

我有一个 JSON 对象列表（从 nosql 数据库接收）并且想要删除或重命名一些键。然后我想再次以 JSON 对象列表的形式返回数据。

这篇 Stackoverflow 帖子很好地介绍了如何使用 mochijson2 。我想我可以使用列表理解来完成JSON 对象的列表。

我遇到的问题是如何在列表理解中删除每个 JSON 对象（或 proplist，如果使用 mochijson2）的键。我可以使用 proplists 的删除功能。但当我尝试在列表理解中做到这一点时，我没有成功。

这是上下文的一些代码：

A = <<"[{\"id\": \"0129\", \"name\": \"joe\", \"photo\": \"joe.jpg\"  }, {\"id\": \"0759\", \"name\": \"jane\", \"photo\": \"jane.jpg\"  }, {\"id\": \"0929\", \"name\": \"john\", \"photo\": \"john.jpg\" }]">>. 
Struct = mochijson2:decode(A). 
{struct, JsonData} = Struct,
{struct, Id} = proplists:get_value(<<"id">>, JsonData),

非常感谢用代码说明的任何建议。

原文

I have a list of JSON objects (received from a nosql db) and want to remove or rename some keys. And then I want to return data as a list of JSON objects once again.

This Stackoverflow post provides a good sense of how to use mochijson2. And I'm thinking I could use a list comprehension to go through the list of JSON objects.

The part I am stuck with is how to remove the key for each JSON object (or proplist if mochijson2 is used) within a list comprehension. I can use the delete function of proplists. But I am unsuccessful when trying to do that within a list comprehension.

Here is a bit code for context :

A = <<"[{\"id\": \"0129\", \"name\": \"joe\", \"photo\": \"joe.jpg\"  }, {\"id\": \"0759\", \"name\": \"jane\", \"photo\": \"jane.jpg\"  }, {\"id\": \"0929\", \"name\": \"john\", \"photo\": \"john.jpg\" }]">>. 
Struct = mochijson2:decode(A). 
{struct, JsonData} = Struct,
{struct, Id} = proplists:get_value(<<"id">>, JsonData),

Any suggestions illustrated with code much appreciated.

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逆流 2024-10-03 07:36:32

您可以使用lists:keydelete(Key, N, TupleList) 返回删除了某些元组的新元组列表。因此，在列表理解中，对于每个条目提取元组列表（或 proplists），并创建一个删除键的新结构：

B = [{struct, lists:keydelete(<<"name">>, 1, Props)} || {struct, Props} <- Struct].

给出：

[{struct,[{<<"id">>,<<"0129">>},
          {<<"photo">>,<<"joe.jpg">>}]},
 {struct,[{<<"id">>,<<"0759">>},
          {<<"photo">>,<<"jane.jpg">>}]},
 {struct,[{<<"id">>,<<"0929">>},
          {<<"photo">>,<<"john.jpg">>}]}]

和

iolist_to_binary(mochijson2:encode(B)).

给出：

<<"[{\"id\":\"0129\",\"photo\":\"joe.jpg\"},{\"id\":\"0759\",\"photo\":\"jane.jpg\"},{\"id\":\"0929\",\"photo\":\"john.jpg\"}]">>

顺便说一句，使用lists / *元组列表函数要快得多，但是有时比 proplists/* 函数稍微不太方便： http ://sergioveiga.com/index.php/2010/05/14/erlang-listskeyfind-vs-proplistsget_value/

You can use lists:keydelete(Key, N, TupleList) to return a new tuple list with certain tuples removed. So in the list comprehension, for each entry extract the tuple lists (or proplists), and create a new struct with the key removed:

B = [{struct, lists:keydelete(<<"name">>, 1, Props)} || {struct, Props} <- Struct].

gives:

[{struct,[{<<"id">>,<<"0129">>},
          {<<"photo">>,<<"joe.jpg">>}]},
 {struct,[{<<"id">>,<<"0759">>},
          {<<"photo">>,<<"jane.jpg">>}]},
 {struct,[{<<"id">>,<<"0929">>},
          {<<"photo">>,<<"john.jpg">>}]}]

and

iolist_to_binary(mochijson2:encode(B)).

gives:

<<"[{\"id\":\"0129\",\"photo\":\"joe.jpg\"},{\"id\":\"0759\",\"photo\":\"jane.jpg\"},{\"id\":\"0929\",\"photo\":\"john.jpg\"}]">>

By the way, using the lists/* tuple lists functions are much faster, but sometimes slightly less convenient than the proplists/* functions: http://sergioveiga.com/index.php/2010/05/14/erlang-listskeyfind-vs-proplistsget_value/

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