Register variables in with_items loop in Ansible playbook

Question

I've got a dictionary with different names like

vars:
    images:
      - foo
      - bar

Now, I want to checkout repositories and afterwards build docker images only when the source has changed. Since getting the source and building the image is the same for all items except the name I created the tasks with with_items: images and try to register the result with:

register: "{{ item }}"

and also tried

register: "src_{{ item }}"

Then I tried the following condition

when: "{{ item }}|changed"

and

when: "{{ src_item }}|changed"

This always results in fatal: [piggy] => |changed expects a dictionary

So how can I properly save the results of the operations in variable names based on the list I iterate over?

Update: I would like to have something like that:

- hosts: all
  vars:
    images:
      - foo
      - bar
  tasks:
    - name: get src
      git:
        repo: git@foobar.com/repo.git
        dest: /tmp/repo
      register: "{{ item }}_src"
      with_items: images

    - name: build image
      shell: "docker build -t repo ."
      args:
        chdir: /tmp/repo
      when: "{{ item }}_src"|changed
      register: "{{ item }}_image"
      with_items: images

    - name: push image
      shell: "docker push repo"
      when: "{{ item }}_image"|changed
      with_items: images

Answer 1

So how can I properly save the results of the operations in variable names based on the list I iterate over?

You don't need to. Variables registered for a task that has with_items have different format, they contain results for all items.

- hosts: localhost
  gather_facts: no
  vars:
    images:
      - foo
      - bar
  tasks:
    - shell: "echo result-{{item}}"
      register: "r"
      with_items: "{{ images }}"

    - debug: var=r

    - debug: msg="item.item={{item.item}}, item.stdout={{item.stdout}}, item.changed={{item.changed}}"
      with_items: "{{r.results}}"

    - debug: msg="Gets printed only if this item changed - {{item}}"
      when: item.changed == true
      with_items: "{{r.results}}"