User defined actions are created using the
defaction keyword. The
defaction keyword closely follows the syntax of functions. User-defined actions allow for data preprocessing and the execution of one or more actions. User-defined actions are useful for wrapping actions to allow for composite actions or a cleaner syntax surrounding existing actions for a common use case.
The parameters are a possibly empty, comma-separated list of variable names. All parameters can be assigned a default value. Zero or more declarations can be included to prepare data for the action block.
The action block is the same as the action block in a rule. Any action, including a user-defined action, can be used in the action block. Actions can be simple or compound. A simple action is a valid action block. For example, the following defines an action called
send_warning using the
Compound actions work the same as a rule. Suppose, for example, that in addition to putting up a notification, you wished to use send_directive:
send_warning only has meaning in an action context within a rule. Because user-defined actions are first-class values (i.e., they can be returned as the result of executing an expression), they can be passed into functions or other user-defined actions and returned as the result from a function. You can thus write recursive actions.