jq：如果字段存在则映射对象答案

【问题标题】：jq: map object if field existsjq：如果字段存在则映射对象
【发布时间】：2021-12-22 22:56:44
【问题描述】：

这是我的jq代码：

def pick_nationality:
  {nation: {country: .NACIONALITAT, code: "some code"} };

def pick_surname:
  {name: {surname: .SURNAME, code: "some code"} };

map([pick_nationality, pick_surname])

当输入对象上不存在某些.NACIONALITAT 或.SURNAME 时会出现问题：

{
  "SURNAME": "surname1"
}
{
  "NACIONALITAT": "nacionalitat1"
}

结果：

[
  [
    {
      "nation": {
        "country": null,
        "code": "some code"
      }
    },
    {
      "name": {
        "surname": "surname1",
        "code": "some code"
      }
    }
  ],
  [
    {
      "nation": {
        "country": "nacionalitat1",
        "code": "some code"
      }
    },
    {
      "name": {
        "surname": null,
        "code": "some code"
      }
    }
  ]
]

问题是当.NATIONALITAT 字段不存在时，我需要避免pick_natinality...

期望的结果是：

[
  [
    {
      "name": {
        "surname": "surname1",
        "code": "some code"
      }
    }
  ],
  [
    {
      "nation": {
        "country": "nacionalitat1",
        "code": "some code"
      }
    }
  ]
]

有什么想法吗？

【问题讨论】：

标签： jq

【解决方案1】：

当相关字段缺失时，让函数不返回任何内容。

def pick_nationality:
  select(.NACIONALITAT) |
  {nation: {country: .NACIONALITAT, code: "some code"} };

def pick_surname: 
  select(.SURNAME) |
  {name: {surname: .SURNAME, code: "some code"} };

map([pick_nationality, pick_surname])

Demojqplay

【讨论】：

【解决方案2】：

您可以将 del 用于相应的 null 值，例如

jq -r 'del(.[][] | select(.nation.country == null and .name.surname== null))'

Demo

【讨论】：

【解决方案3】：

您可以在捕获值之前添加测试：

def pick_nationality:
  if has("NACIONALITAT")
  then {nation: {country: .NACIONALITAT, code: "some code"} }
  else empty end;

def pick_surname: 
  if has("SURNAME")
  then {name: {surname: .SURNAME, code: "some code"} }
  else empty end;

map([pick_nationality, pick_surname])

【讨论】：