Mapping with expressions

In 20 seconds

An expression is text between double curly braces, like {{ $input.title }}, that AWFlow replaces with a value while the node runs. It runs once for every item, so the same setting can produce a different value for each one. Use $input for the incoming item, $('Step name') for another step, and $run for a variable set earlier in the run.

See it happen

Edit Fields receives two orders and builds two fields from expressions. Each expression is worked out once per item.

Example run: Orders, 2 items → Edit Fields, ran 2 times, 2 items. name = {{ upper(trim($input.first)) + " " + $input.last }} · size = {{ $input.total > 100 ? "big order" : "small order" }}

1. Orders 2 items →
2. Edit Fields ran 2× 2 items name, size from expressions

Output of Edit Fields Table JSON

#	name	size
0	ADA Lovelace	big order
1	GRACE Hopper	small order

name = {{ upper(trim($input.first)) + " " + $input.last }} · size = {{ $input.total > 100 ? "big order" : "small order" }}

The three things you can read

Write	Reads	Example
$input	The item this node is working on	{{ $input.title }}, {{ $input.metadata.description }}, {{ $input.0.name }}
$('Step name')	The output of another step, by its label	{{ $('Get Page Metadata').title }}
$run	A variable stored earlier in this run by Set Variable	{{ $run.cursor }}, {{ $run.page.next }}

• Paths use dots, including for list positions: $input.items.0.name is the name of the first entry (counting starts at 0).
• Step names must match the node label exactly, spaces and capitals included. Renaming the step breaks the reference.
• $('…') and items: a step directly connected to this one gives the matching item; a step further back gives its whole output. See Item linking.
• Missing values in $input and $('…') become empty text, so a typo doesn’t stop the run. Check Preview from last run under the field.
• $run is strict: reading a variable that hasn’t been set yet fails the step with an error that names it and lists the variables set so far. Read a variable only in steps that run after the Set Variable node. When a read might come first, the canvas warns you; see reading a variable before it is set.

You rarely type $input yourself: drag a field from the Input panel and the expression is written for you. See Mapping in the UI.

Text around values

Mix your own words with expressions in any text setting:

Prompt

Summarize the page at {{ $input.url }}.
Title: {{ $input.title }}

Operators

Fallbacks: || returns the first value that isn’t empty.

Expression

{{ $input.title || "Untitled page" }}

Maths: + - * / %, with the usual precedence and parentheses.

Expression

{{ 5 + 3 * 2 }}        → 11
{{ (5 + 3) * 2 }}      → 16
{{ $input.price * 1.2 }}

Joining text: + joins text when either side is text.

Expression

{{ $input.first + " " + $input.last }}

Comparisons and choices: == != < <= > >=, logic with && || !, and condition ? ifYes : ifNo.

Expression

{{ $input.total > 100 ? "big order" : "small order" }}
{{ $input.status == "open" && $input.priority == "high" }}

Helper functions

Text	Numbers	Lists and general
upper(s) lower(s) trim(s)	round(n) floor(n) ceil(n) abs(n)	length(x)
replace(s, find, with)	min(a, b, …) max(a, b, …)	includes(list, value)
split(s, sep) slice(s, start, end)	number(x)	join(list, sep) slice(list, start, end)
str(x)		default(value, fallback)

Expression

{{ upper(trim($input.name)) }}
{{ join($input.tags, ", ") }}
{{ default($input.title, "Untitled") }}
{{ length($input.items) > 0 ? "has items" : "empty" }}

Expressions are sandboxed: only these functions exist. There are no variables of your own, no method calls like .toUpperCase(), and no access to anything outside the values you reference.

Expression, Edit Fields or Code?

• Expression One setting needs a small change: a fallback, a join, a choice. Example {{ $input.title || "Untitled" }} inside the setting
• Edit Fields → Several later steps need the same cleaned-up fields. Example Build name and size once, then read $input.name everywhere. one node, no code
• Code → The logic needs loops, grouping or parsing. Example Count orders per customer. Python

You’ll notice this when…

The result shows expression text, like $(‘Get Metadata’).title, instead of a value

AWFlow couldn’t work the expression out, so it left the text as it was rather than failing the step. The usual cause is a $('…') name that differs from the node label. Copy the label from the canvas, or drag the field from the Input panel instead.

The value is empty

The path doesn’t exist on this item. Open the previous step’s Output tab and compare: maybe the value is nested ($input.data.title), or the step output one item holding a list ($input.links.0).

The step fails with “Variable … has not been set at this point in the run”

A $run variable is read before the Set Variable step that writes it, for example from a parallel branch. Connect the reading step after the Set Variable step.

An expression with .toUpperCase() comes out as plain text

Methods and outside functions aren’t available, so the expression can’t be worked out and its text is kept as is. Use the helper functions above, such as upper(…), or move the logic to the Code node.

Next

Next concept: Item linkingWhich item a reference to an earlier step returns.

Practise itRecipes that build prompts and messages from page data.