07_conditions_and_loops.yaml

---
# can you conditionally run a task ?  
# of course, let's throw in a loop and only print
# the family if the father is named "john"
- name: print only John's family
  hosts: localhost
  vars_files:
    - vars/families.yaml

  vars:
    an_undefined_variable: 
    a_defined_variable: "I am defined"
  tasks:
    - name: print only John's family
      debug:
        var: family

      # only print the item when the condition is true
      when: item.father == 'John'

      # loop over the families
      with_items: "{{ families }}"

      # loop control is optional but can be useful
      loop_control:
        loop_variable: family
        label: "{{ family.father }}'s family has {{ family.children | length }} children"

    # can we put a condition if a variable contains a value ? (is defined)
    - name: print when a variable is defined
      debug:
        msg: "I am defined"
      when: a_defined_variable is defined

    # can we do this if it does not contain a value ? (undefined / or null)
    - name: print when a variable is not defined
      debug:
        msg: "I am not defined"
      when: an_undefined_variable is not defined

    # now lets inverse the last two tasks logically
    - name: skip when a variable is not defined
      debug:
        msg: "I am not defined"
      when: a_defined_variable is not defined

    - name: skip when a variable is defined
      debug:
        msg: "I am defined"
      when: an_undefined_variable is defined