# Action Params

An *action param* defines a named input that a caller passes into an action when it is triggered. Within the action, the value is available as a context param and can be referenced in [conditions](/reference/platform-concepts/conditions.md), [filters](/reference/platform-concepts/filters.md), and [functions](/reference/platform-concepts/functions.md).

Action params make actions reusable. Instead of building a separate action for every variation of the same logic, you define the action once and let the caller supply the values that differ. A common example is a navigation action in an app: the action accepts an action param with the data type `View`, and a single [Navigate](/library/action-nodes/navigate.md) action node navigates to whatever view the caller specifies.

### What an action param can accept

An action param's data type determines what the caller can pass in:

* **Primitive values** — strings, numbers, booleans, and other basic value types available on the platform.
* **Enumerated types** — values from an [enumerated type](/reference/data-model/enumerated-types.md) defined in the solution. An enumerated-type param can have cardinality one (a single value) or many (a list of values).
* **Schemas** — structured data, with the schema defined inline on the param. This allows a caller to pass complex, nested data into the action without first modelling it as an object class. See [schemas](/reference/platform-concepts/schemas.md).
* **References to object classes** — a reference to a single record (cardinality one) or a set of records (cardinality many) from an object class. See [object classes](/reference/data-model/object-classes.md) for more information on data types.
* **Views** — a reference to a [view](/reference/apps/ui/views.md) in an app. This data type is only available in app actions.

### Creating an action param

Action params are defined on their parent action, alongside action variables and action data sources. The authoring surface differs between flows and apps:

* **In a flow action,** action data is configured on the **Action data** tab in the flow action editor.
* **In an app action,** action data is configured under **Action settings** in the right-side panel.

When adding an action param, choose a name and a data type. If the data type is set to schema, the **Edit schema** dialog opens where the schema structure is defined inline. An action param can be marked as required, which means the caller must always provide a value. If it is not required, a default value can be specified.

### Passing action params

When an action is triggered, the caller maps values into the action's params. How this happens depends on the trigger:

**From the UI.** When an action is triggered by an [event handler](/reference/platform-concepts/event-handlers.md), action param values are configured on the event handler. Each param is bound to a value from the calling context — a data source property, an app variable, or a function result.

**From another action.** When an action is called by [Run Action](/library/action-nodes/run-action.md) or a flow is called by [Run Flow](/library/action-nodes/run-flow.md), the target action's params are displayed on the action node. Each param is bound to a value from the calling context in the same way — the only difference is that Run Action calls an action in the same app or flow, while Run Flow calls a flow from an app or from another flow. Because action params support schemas, structured data can be passed directly into an action or flow without first persisting it.

### Reusing action params across actions

An action param — including any inline schema it carries — can be copied and pasted into another action. This works across actions in the same flow, across different flows, and into app actions. Copy-paste is the primary mechanism for replicating a param definition, and it carries the full schema structure along with it.

### Properties

| Property          | Description                                                                                                                                                                                                                  |
| ----------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Name**          | A descriptive name.                                                                                                                                                                                                          |
| **Data Type**     | The type of data accepted as input for this parameter. See [object classes](/reference/data-model/object-classes.md) for more information.                                                                                   |
| **Schema**        | <p><em>Available if <strong>Data Type</strong> is <strong>Schema</strong></em><br><br>Define the schema structure that the param accepts.</p>                                                                                |
| **Cardinality**   | <p><em>Available for enumerated types and object-class references.</em><br><br>Whether the param accepts a single value (<strong>One</strong>) or a list of values (<strong>Many</strong>).</p>                              |
| **Required**      | Require that a value for this parameter is always specified when the action is triggered.                                                                                                                                    |
| **Default Value** | <p><em>Not available if Required is enabled or if data type is a reference to an object class or enum.</em><br><br>Specify a default value to use in the case that a value is not provided when the action is triggered.</p> |


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