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Predicates are used to allow the conditional execution of
Actions. They form the passive, watching part of rules,
the trigger. All defined predicates are made available as methods
of the object a rule script is executed for. As they take
precedence any original method with the same name as a predicate
will be shadowed.
The interpreter cannot enforce this, but predicates have to be
functions, i.e. they have to return a value. Another important point
to consider when writing one is that they are trusted by the system
and not restricted to the safe environment created for the rule
scripts and the actions. Because of this it is not possible to define
new predicates from within a rule script, this would pose a serious
security risk.
The body of predicates has access to the input object too, in the
form of the variable input containing the name of its command.
The variable effectively operates like the this/self reference in
other object oriented languages.
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Predicates
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| Subcmd |
Description |
| ::fmail::predicate |
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name arguments body
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Defines a new command, just like proc and its cousin
::fmail::action. The command has access to
the input object and the full resources of the trusted
environment. It is made available as method of the input
object itself and thus introduced into rule scripts.
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