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constrained_action(prog_tools) constrained_action(prog_tools)

NAME

constrained_action - just like an action but it checks some constraints first

DESCRIPTION

The constrained_action class is actually a subclass of logic that should look like an action. It allows one to specify a list of constraints to be checked before executing its tick_actions. If a constraint fails then its failed actions are executed. Each constraint has it's own failed actions. If the failed action corrects the problem then it should end with a object_name continue! message to indicate that the problem has been resolved. Once all the constraints have been satisfied then the tick_actions are executed. Since this class is a child of logic all of logic's methods can be used to test for conditions. See example below.

SUPERCLASS

logic

INSTANCE VARIABLES

constraint_name This is the name of the constraint currently being sent commands. constraints= and failed_actions= message will be setting this constraint.

value In evaluating constraints and failed_actions the scalar value must be set. A constraint should set this value to 1 if it succeded and 0 if it failed. A failed_action should set this value to 1 if it was able to correct the problem that caused the constraint to fail in the first place.

MESSAGES

constraint[=,+]actions Set the actions for the constraint. Make sure these actions set the instances value to 1 (TRUE) or 0 (FALSE).

continue! Typically used in a failed_action to tell the constrained_action object that the failed constraint has been taken care of. i.e. do not abort processing due to this failed constraint, it has been taken care of.

failed_actions[=,+]actions Set the actions to execute if the constraint is not satisfied. These actions should set the instance variable value to 1 if they have corrected the problem.

new_constraint=name Create a new constraint and set the current constrain name.

EXAMPLE

-- Create a simple constrained_action with only one constraint -- creates a new constraint named need_popup_script -- it checks to see if an action has been defined -- if not then read in the script that contains the action -- tell the constrained_action object to continue processing -- if everything is ok then do the satisfied action

constrained_action new: simple_action new_constraint=`need_popup_script' constraint=`simple_action defined: popup_action;' failed_actions=`<popup.scr' failed_actions+`simple_action continue!;' satisfied_actions=`popup_action do!;' ;

simple_action tick!;