Ansible: loops and registering results of commands

Ansible has a great feature of registering results of a performed step. But recently I stumbled upon a need to do it against actions from a loop and then using the registered result in the next steps which are also looped. Most often, it can be used to perform some action only in case if a previous action changed a file.

Firstly, we register `action_state` variable. Its sub-dictionary `results` contains attribute `changed` which can be accessed as `action_state.results.changed`. Now, we need to get it into use in the next looped step. It can be done with ease using `with_together` operator:

- name: copy a file
    src: '{{ source }}'
    dest: '{{ target }}'
  with_items: yourlist
  when: item.state == 'present'
  register: action_state

- name: create .ssh dir if file changed in the previous step
  sudo_user: '{{ item.0.user }}'
    state: directory
    path: '/home/{{ item.0.user }}/.ssh'
    mode: 0700
  - yourlist
  - action_state.results
  when: item.1.changed and item.0.state == 'present'

Here, for the `yourlist` we copied some files to a target machine (i.e. public keys to some temp location) in the loop and then for each of the files performed an action only if a file was changed.