Foreach

Foreach on Github

The foreach state requires the array attribute to loop over. The difference to other states is that the data in the action of the foreach function is not getting the state data of the flow but the values provided in the array.

Simple Foreach

This is the most basic example. It shows that each action call in the foreach loop has it's own object during execution. In the flow scope there is a variable .names. But the array definition uses jq to iterate through .names and creates a list of JSON objects with the variable name. This means that each action only sees an object with the value name and has no access to names.

Simple Foreach

direktiv_api: workflow/v1

functions:
- id: echo
  image: direktiv/echo:dev
  type: knative-workflow

states:

- id: data
  type: noop
  log: preparing foreach data
  transform:
    names:
    - hello
    - world
    - goodbye
  transition: foreach

- id: foreach
  type: foreach
  array: 'jq([.names[] | { name: . }])'
  action:
    function: echo
    input: 'jq(.)'

The output for this flow should be something like the following:

Output

{
  "names": [
    "hello",
    "world",
    "goodbye"
  ],
  "return": [
    {
      "name": "hello"
    },
    {
      "name": "world"
    },
    {
      "name": "goodbye"
    }
  ]
}

Foreach with JQ

This examples shows how to use JQ for a more complex foreach scenario. It generates an array based on .data in the first state. The JQ command is storing the state data .otherdata in the variable od. This result will be piped into the actual array generation with .data[]. In this case it is more obvious how each foreach action gets it's own JSON object. In this case the JQ command sets the name to the name in the array, time to the actual time with the JQ time function. The last attribute otherdata passes the original value from the flow state data into the action.

JQ Foreach

direktiv_api: workflow/v1

functions:
- id: echo
  image: direktiv/echo:dev
  type: knative-workflow

states:

- id: data
  type: noop
  transform:
    data:
    - name: key1
      value: value1
    - name: key2
      value: value2
    - name: key3
      value: value3
    otherdata: somedata
  transition: foreach

- id: foreach
  type: foreach
  array: 'jq(.otherdata as $od | [.data[] | { name: .name, time: now, otherdata: $od }])'
  action:
    function: echo
    input: 'jq(.)'

Output

{
  "data": [
    {
      "name": "key1",
      "value": "value1"
    },
    {
      "name": "key2",
      "value": "value2"
    },
    {
      "name": "key3",
      "value": "value3"
    }
  ],
  "otherdata": "somedata",
  "return": [
    {
      "name": "key1",
      "otherdata": "somedata",
      "time": 1680972341.2246315
    },
    {
      "name": "key2",
      "otherdata": "somedata",
      "time": 1680972341.224634
    },
    {
      "name": "key3",
      "otherdata": "somedata",
      "time": 1680972341.2246354
    }
  ]
}

Foreach with JS

This example uses Javascript to achieve the same outcome. If data structures are getting too complex it might be better to use Javascript for readability. If Javascript is used Direktiv passes in an object data which contains the flow state. Data can be accessed in the usual way like data["otherdata"]. In the case of a foreach the Javascript function needs to return an array.

JS Foreach

direktiv_api: workflow/v1

functions:
- id: echo
  image: direktiv/echo:dev
  type: knative-workflow

states:
- id: data
  type: noop
  transform:
    data:
    - name: key1
      value: value1
    - name: key2
      value: value2
    - name: key3
      value: value3
    otherdata: somedata
  transition: foreach
- id: foreach
  type: foreach
  array: |
    js(
      // empty array
      const items = []

      // loop over "data" attribute created in first state of flow
      for (let i = 0; i < data["data"].length; i++) { 
          // create object and set attributes
          item = new Object();  
          item.name = data["data"][i]["name"]
          item.time = Date.now()
          item.otherdata = data["otherdata"]

          // add item
          items[i] = item
      }

      // return array of items
      return items
    )
  action:
    function: echo
    input: 'jq(.)'