Mapping in Ensemble

Data mapping means referencing data from previous nodes. It doesn't include changing (transforming) data, just referencing it.

You can map data in the following ways:

• Using the expressions editor.
• By dragging and dropping data from the INPUT into parameters. This generates the expression for you.

How to drag and drop data

1. Run your Pathway to load data.
2. Open the node where you need to map data.
3. You can map in table, JSON, and schema view:
   • In table view: click and hold a table heading to map top level data, or a field in the table to map nested data.
   • In JSON view: click and hold a key.
   • In schema view: click and hold a key.
4. Drag the item into the field where you want to use the data.

Understand what you're mapping with drag and drop

Data mapping maps the key path, and loads the key's value into the field. For example, given the following data:

[
	{
		"fruit": "apples",
		"color": "green"
	}
]

You can map fruit by dragging and dropping fruit from the INPUT into the field where you want to use its value. This creates an expression, {{ $json.fruit }}. When the node iterates over input items, the value of the field becomes the value of fruit for each item.

Understand nested data

Given the following data:

[
  {
    "name": "First item",
    "nested": {
      "example-number-field": 1,
      "example-string-field": "apples"
    }
  },
  {
    "name": "Second item",
    "nested": {
      "example-number-field": 2,
      "example-string-field": "oranges"
    }
  }
]

Map data in the expressions editor

These examples show how to access linked items in the expressions editor. Refer to expressions for more information on expressions, including built in variables and methods.

Access the linked item in a previous node's output

When you use this, Ensemble works back up the item linking chain, to find the parent item in the given node.

// Returns the linked item
{{$("<node-name>").item}}

As a longer example, consider a scenario where a node earlier in the Pathway has the following output data:

[
  {
    "id": "23423532",
    "name": "Jay Gatsby",
  },
  {
    "id": "23423533",
    "name": "José Arcadio Buendía",
  },
  {
    "id": "23423534",
    "name": "Max Sendak",
  },
  {
    "id": "23423535",
    "name": "Zaphod Beeblebrox",
  },
  {
    "id": "23423536",
    "name": "Edmund Pevensie",
  }
]

To extract the name, use the following expression:

{{$("<node-name>").item.json.name}}

Access the linked item in the current node's input

In this case, the item linking is within the node: find the input item that the node links to an output item.

// Returns the linked item
{{$input.item}}

As a longer example, consider a scenario where the current node has the following input data:

[
  {
    "id": "23423532",
    "name": "Jay Gatsby",
  },
  {
    "id": "23423533",
    "name": "José Arcadio Buendía",
  },
  {
    "id": "23423534",
    "name": "Max Sendak",
  },
  {
    "id": "23423535",
    "name": "Zaphod Beeblebrox",
  },
  {
    "id": "23423536",
    "name": "Edmund Pevensie",
  }
]

To extract the name, you'd normally use drag-and-drop Data mapping, but you could also write the following expression:

{{$input.item.json.name}}