addedValues Plugin

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Triggers

A Trigger is a question with a Yes or No answer that is asked when an addedValue entity created or changed and an action to take if the answer is Yes. Triggers are a very powerful way to have your site react to data entry, for example, a trigger might enter a message into the site structure at a url which depends on addedValue plugin variable values. In that example, the action is site structure change; the condition might be that a varibale in the message have a certain value or it might be more complex.

The question is entered as boolean expression of addedValue variables. When the test is done , the actual valeus fo the variables from the entity that changed are used. The boolean expression in condition is built from unindexed or indexed variables or global variables. It may contain AND and OR boolean operators, NOT operations and arithmetic and string relations and parenthesised sub-expressions. It can reference variables that are globals (belong to the site) or that match "Applies To' value of the trigger, and if the groupname of the trigger is not 'None" then it is restricted to variables from that group.

The action is one of a set of alternatives installed by your server administrator; or may be an updater you write yourself. If no candidates exist, triggers are disabled. The administrator may restrict the use of a trigger to one website because if a trigger is installed in the #tools table of a website, only that website can make use of the trigger. If the action becomes unusable after definition, perhaps because a script was removed or isnt available, the trigger cannot be used and is listed in the selection menu in red and struck through.

Errors in triggers are always logged; they are enteed in the log under the category which is the name of the website.

addedValues ships with several useful triggers, which must be enabled by the site administrator.

AddedValues counts the number of times each trigger is tested (the condition is evaluated) and the number of times it "fires" (the value is true) and reports these counters along with the options on the trigger main page.

Triggers can be difficult to test, because of their generality and the possible interaction if several fire at one time. To make this easier, there is a way to apply triggers to a set of messages, gems, etc. by using a query to generate a hit list. That and the type of trigger event to simulate can be set in a form on the triggers page. The effect of the triggers on the hit list entries is permanent, this is not a test feature!