---
title: "Action set"
description: "Sets or changes dialog constants: values, expressions, methods on objects."
---

# Action `set`

> **System ID:** `action_set`

## Description

Writes dialog state constants. Values can be strings with placeholders, math expressions, or a method call on an object in constants. Constants are processed sequentially — later ones can reference earlier ones.

Do not place `set` directly before a connect-to-operator node: the change may be overwritten. Better to place it after the connection.

## Events (scenario branches)

| Event | When it occurs |
|-------|----------------|
| **default** | Constants written |

## Parameters

No fixed parameters. Config is a JSON object: key = constant name, value = what to write.

| Element | Type | Required | Default | Description |
|---------|------|----------|---------|-------------|
| *(arbitrary keys)* | string / object | no | — | String, expression, or `{ "method", "object", "params" }` for a method on an object |

## Configuration example

```json
{
  "price": "100",
  "quantity": "2",
  "total": "{{price}}*{{quantity}}",
  "greeting": "Вітаємо, {{name}}!"
}
```

## Related docs

- [Actions reference](/en/actionjail/reference/actions-reference.md)