在 Ansible/Jinja2 中设置 var 的 case 语句 [英] Case statement for setting var in Ansible/Jinja2

问题描述

我将 Ansible 与 Jinja2 模板一起使用，这是我无法在 Ansible 的文档中找到解决方案或在谷歌上搜索 Jinja2 示例的情况.这是我想在 Ansible 中实现的逻辑:

I'm using Ansible with Jinja2 templates, and this is a scenario that I can't find a solution for in Ansible's documentation or googling around for Jinja2 examples. Here's the logic that I want to achieve in Ansible:

if {{ existing_ansible_var }} == "string1"
  new_ansible_var = "a"
else if {{ existing_ansible_var }} == "string2"
  new_ansible_var = "b"
<...>
else
  new_ansible_var = ""

我可能可以通过结合几种技术来做到这一点，这里的变量赋值:在 jinja 中设置变量，这里的条件比较:http://jinja.pocoo.org/docs/dev/templates/#if-expression，以及这里的默认过滤器:https://docs.ansible.com/playbooks_filters.html#defaulting-undefined-variables ,

I could probably do this by combining several techniques, the variable assignment from here: Set variable in jinja, the conditional comparison here: http://jinja.pocoo.org/docs/dev/templates/#if-expression, and the defaulting filter here: https://docs.ansible.com/playbooks_filters.html#defaulting-undefined-variables ,

...但我觉得这太过分了.有没有更简单的方法来做到这一点?

...but I feel like that's overkill. Is there a simpler way to do this?

推荐答案

如果您只想根据 existing_ansible_var 的值在模板中输出一个值，您只需使用 dict 并提供它使用 existing_ansible_var.

If you just want to output a value in your template depending on the value of existing_ansible_var you simply could use a dict and feed it with existing_ansible_var.

{{ {"string1": "a", "string2": "b"}[existing_ansible_var] | default("") }}

你可以用同样的方式定义一个新变量:

You can define a new variable the same way:

{% set new_ansible_var = {"string1": "a", "string2": "b"}[existing_ansible_var] | default("") -%}

<小时>

如果 existing_ansible_var 可能不一定被定义，你需要用一个 default() 来捕捉它，它在你的字典中不存在:

---

In case existing_ansible_var might not necessarily be defined, you need to catch this with a default() which does not exist in your dict:

{"string1": "a", "string2": "b"}[existing_ansible_var | default("this key does not exist in the dict")] | default("")

<小时>

您也可以在剧本中定义它，然后在模板中使用 new_ansible_var:

vars: 
   myDict:
     string1: a
     string2: b
   new_ansible_var: '{{myDict[existing_ansible_var | default("this key does not exist in the dict")] | default("") }}'

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