use dynamic variable as dictionary name - ansible

Question

I have playbook as below:
- name: fetch host group name
set_fact:
group_name: '{{ group_names[0] }}'
- name: get memory and storage minimum requirements
set_fact:
min_memory: "{{ group_name.memory }}"
min_storage: "{{ group_name.storage }}"
In defaults/main.yml
#memory and storage settings
primary:
memory: 32
storage: 128
my inventory host is in primary group.
when I run playbook, I am seeing below error.
TASK [ansible-elastic-cloud-enterprise : get memory and storage minimum requirements] ****************************************************************************************************************************
fatal: [192.168.153.5]: FAILED! => {"msg": "The task includes an option with an undefined variable. The error was: 'str object' has no attribute 'memory'\n\nThe error appears to be in '/cygdrive/c/Users/test/Downloads/ansible-elastic-cloud-enterprise-master/roles/ansible-elastic-cloud-enterprise/tasks/base/general/checkmemorystorage.yml': line 7, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: get memory and storage minimum requirements\n ^ here\n"}

Answer 1

you want to use the content of variable like another variable, so use lookup vars:
sample:
- name: dynamic var
hosts: localhost
gather_facts: no
vars:
groupname: ["primary", "secondary"]
primary:
memory: 32
storage: 128
tasks:
- set_fact:
id: "{{ lookup('vars', groupname[0]) }}"
- debug: msg="{{ id.memory }} -- {{ id.storage }} "
result:
ok: [localhost] => {
"msg": "32 -- 128 "
in your case you should write:
- name: fetch host group name
set_fact:
group_name: '{{ lookup("vars", group_names[0] }}'