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Runtime Variables

Need a variable that's not fixed but depends on another request's response? Runtime variables let you capture values from one API call and reuse them in subsequent requests.

What are Runtime Variables?​

Runtime variables are dynamic values that get set during request execution. They're perfect for scenarios like:

  • Capturing an auth token from login and using it in authenticated requests
  • Storing a user ID from a create-user response
  • Saving an order ID to use in later order management calls

Creating Runtime Variables​

Add a /runtime-variables block in your voiden file:

Runtime Variable

Available Data Sources​

  1. From Request ($req) Access data from the current request:

    URL: {{$req.url}}

    Headers: {{$req.headers.Authorization}}

    Content Type: {{$req.contentType}}

    Body: {{$req.body.email}}

    Path Parameters: {{$req.params.userId}}

    Query Parameters: {{$req.query.page}}

  2. From Response ($res) Access data from the API response:

    Status Code: {{$res.statusCode}}

    Response Body: {{$res.body.data.user_id}}

    Headers: {{$res.headers.x-rate-limit}}

    Content Type: {{$res.contentType}}

Accessing Nested Data

  • Objects

    Use dot notation to access nested properties:

    user_email: "{{$res.body.user.contact.email}}"
    api_version: "{{$res.body.meta.api.version}}"

  • Arrays Access array elements by index or let Voiden auto-select:

    1. Specific Index:
    first_item: "{{$res.body.items[0].name}}"
    third_user: "{{$res.body.users[2].id}}"
    1. Auto-select (first match):
      any_product: "{{$res.body.products.name}}"  # Gets first product's name
    any_id: "{{$res.body.ids}}"                 # Gets first ID in array

Example Workflow

  1. First request

    In the first request , add the Runtime block , and attach to a data source for every variable

    Capture Variable

    And run the request by either:

    • Pressing Cmd + Enter (on macOS) or Ctrl + Enter (on Windows/Linux), or
    • Clicking the bright green Play button in the toolbar.

  2. Second request

    Reference the variables using process anywhere

    Access Variable

Best Practices

  • Use descriptive names: session_token instead of token1
  • Handle null cases: Ensure the data path exists before using it
  • Test extraction: Verify runtime variables capture the expected values
  • Chain carefully: Make sure dependent requests execute in the correct order

Runtime variables transform your isolated API calls into connected workflows!