在JQ中获取或默认功能? [英] Get or default function in JQ?

问题描述

假设有一个json文件:

Assuming there is a json file:

{
  "columns": {
    "id": {
      "required": true,
      "type": "integer"
    },
    "name": {
      "required": false,
      "type": "string"
    },
    "description": {
      "type": "string"
    }
  }
}

我想使用jq来获取每一列的值"required"字段.如果字段"required"不存在，则应返回默认值false.

I want to use jq to get the value "required" field for each column. If the field "required" does not exist, it should return the default value false.

特别是:

jq '.columns.id | getOrDefault("required", false)'  # true
jq '.columns.name | getOrDefault("required", false)'  # false
jq '.columns.description | getOrDefault("required", false)'  # false

如何在jq中实现此神奇的getOrDefault()函数?

How to implement this magic getOrDefault() function in jq?

推荐答案

如果字段"required"不存在，则应返回默认值false.

If the field "required" does not exist, it should return the default value false.

要从字面上实现该功能，您可以使用has/1而不是//，例如:

To implement that functionality literally, you would use has/1 rather than //, e.g.:

   .columns.id
   | if has("required") then .required else false end

如果永不将.required字段指定为null，则两种技术(如上使用has和// false)是等效的.

If the .required field is known never to be specified as null, then the two techniques (using has as above and using // false) are equivalent.

您几乎肯定不会定义这样的功能，但是由于您提出以下要求:

You'd almost surely never define such a function, but since you ask:

def getOrDefault($key; $default):
  if has($key) then .[$key] else $default end;

(注意:jq中的参数分隔符是;.)

(NB: The argument separator in jq is ;.)

这篇关于在JQ中获取或默认功能?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！