Loop: for each item

Goal

Run a block once per array item and use the collected results. Time: 15 minutes.

schema: 1
name: Loop names
id: loop-names
blocks:
  - id: names
    kind: code
    language: python
    body: |
      import json; print(json.dumps({"items": ["Ada", "Lin", "Grace"]}))
    outputs:
      type: object
      properties:
        items: { type: array, items: { type: string } }

  - id: each_name
    kind: loop
    for_each: steps.names.items
    max: 20
    body:
      - id: greet
        kind: code
        language: python
        uses: [loop.item, loop.index, loop.count]
        body: |
          import json, os
          d = json.load(open(os.environ["TERMORQ_INPUT"], encoding="utf-8"))["loop"]
          print(json.dumps({"greeting": f"Hello {d['item']} ({d['index']}/{d['count']})"}))
        outputs:
          type: object
          properties:
            greeting: { type: string }

  - id: count_passes
    kind: code
    language: python
    uses: [steps.each_name.results]
    body: |
      import json, os
      r = json.load(open(os.environ["TERMORQ_INPUT"], encoding="utf-8"))["steps"]["each_name"]["results"]
      print(json.dumps({"count": len(r), "first": r[0]["greet"]["greeting"]}))
    outputs:
      type: object
      properties:
        count: { type: number }
        first: { type: string }

Loop facts

Fact	Value
Loop context	`loop.item` (the current element), `loop.index` (starts at 1), `loop.count`
Output	`steps.<loop id>.results`: one object per pass, keyed by child block ID, plus `status` and `exit`
`max`	Defaults to 20, and the ceiling is 100
Passes per run	100 in total, across all loops
Nesting	Up to 2 levels deep
Blocks per file	40, including loop bodies

In the editor, a loop is a frame. Add blocks with the + inside the frame, or drag existing blocks into it. While it runs, the frame shows progress such as 3 of 12. Keep the - id: of each child indented under body: in YAML.

Check your run

count_passes publishes count: 3 and first: "Hello Ada (1/3)". On Runs, greet appears three times, once per pass.

Exercise

Replace the inline names block with a workflow input: declare inputs: names: {type: array, items: {type: string}} and loop over inputs.names.

Details

inputs:
  names:
    type: array
    items: { type: string }
blocks:
  - id: each_name
    kind: loop
    for_each: inputs.names
    body: [ ...same greet block... ]

When you press Run, enter the names. An HTTP trigger can supply them as {"names":["Ada","Lin"]}.