# PDL_ParamExists

## Description

Checks if a named parameter has been passed to a service callback function. You can register a callback function with a service using the PDL_ServiceCallWithCallback API.

All parameters are passed as strings though their underlying types can be `string`, `double`, or `int`. You can extract a named parameter with the PDL_GetParamDouble, PDL_GetParamInt, or PDL_GetParamString APIs.

See Accessing Services for more information and examples.

## Syntax

>     PDL_bool PDL_ParamExists(PDL_ServiceParameters *params, const char *name);

Argument | Description
--- | ---
params | Parameters from which to extract data. This is passed to the callback function from the service and you simply pass it on here without modification.
name | Name of the argument to check.

## Returns

>     PDL_TRUE - Parameter exists.
>     PDL_FALSE - Parameter does not exist.

See also:

- PDL_ServiceCall
- PDL_ServiceCallWithCallback
- PDL_UnregisterServiceCallback
- PDL_GetParamDouble
- PDL_GetParamInt
- PDL_GetParamString