Ansible dynamic variable resolution

Question

Variable derived from another variable - how to get the result

I am using ansible version 2.7

I have the following vars file v1

envs:
  DEV:
    D1:
      Apps:
       App1:
         App_name: A1
       App2:
         App_name: A2
  SIT:
    S1:
      Apps:
       App1: 
         App_name: K1
       App1: 
         App_name: K2

I am passing env_type as DEV or SIT and env_name as corresponding D1 or S1.

my command line is

ansible-playbook test.yml -e "env_type='SIT' env_name='S1'"

I am expecting the code to return all the App_name fields for SIT S1 as a list, for further processing.

Can you please suggest how to structure the code.

Answer 1

You could do something like this:

---
- hosts: local
  connection: local
  gather_facts: no
  vars:
    envs:
      DEV:
        D1:
          Apps:
            App1:
              App_name: A1
            App2:
              App_name: A2
      SIT:
        S1:
          Apps:
            App1:
              App_name: K1
            App2:
              App_name: K2
  tasks:
    - set_fact:
        app_list: '{{ envs[env_type][env_name]["Apps"].values() | map(attribute="App_name") | list}}'

Use the values method of the Apps object, map over them to get the attribute App_name, and then convert the result to a list.

You don't need to use the set_fact module, but I find it useful when I need to generate facts dynamically.