Including One Trigger in Another

The INCLUDE Command

The #INCLUDE command enables you to use the same trigger more than once without rewriting it.

To include the same trigger elsewhere, use the following syntax (note that there is no semi-colon at the end of the statement):

#INCLUDE form_name / trigger_name
#INCLUDE form_name / form_column_name / trigger_name

When a trigger is included in one or more other triggers, the entire contents of the former are inherited by the latter. Thus, if the CHECK-FIELD trigger for the TYPE column in the PART form is identical to the CHECK-FIELD trigger for the TYPE column in the LOGPART form, you could write the trigger for one column and include it in the other:

CHECK-FIELD for TYPE column in PART form:

CHECK-FIELD for TYPE column in LOGPART form:

Moreover, you can write more statements to the latter (including) trigger which do not apply to the former (included) trigger (before or after the include command).

In contrast, any additions to the included trigger will automatically be attached to the including trigger as well. That is, if changes are made in an included trigger, this will affect all forms that include it; thus, all forms involved will have to be prepared as executable files by the form preparation mechanism.

If the included trigger is deleted, the error will be revealed during the form preparation of any forms that include that trigger.

Tip: To view the original trigger, move to the #INCLUDE line and press F6. The trigger text appears in the sub-level form, Row & Form Triggers – Text.

See also Form Triggers.

Using Buffers

Often, it is more efficient to include only a portion of a trigger. That is, several triggers may share the same set of SQL statements, but each trigger also has additional statements of its own. In such a case, a special type of trigger, called a “buffer,” should be defined. This buffer should hold all the shared SQL statements and it should be included in any trigger that uses this group of statements.

Example: Almost no document in the system (e.g., Goods Receiving Voucher, Customer Shipments, Customer Returns) can be revised once it’s final. The relevant sub-level forms (Received Items, Shipped Items, Returned Items) should therefore include the same check. Thus, the PRE-INSERT trigger of all these sub-level forms includes the same trigger that performs the check:


Naming Buffers

A buffer may either be numbered (BUF1, BUF2, BUF3, ..., BUF19) or assigned a trigger name that hints at its usage. Before any buffer name can be used, it must first be added to the List of Triggers form, which can be accessed by pressing F6 from the Row & Form Triggers form or from the Form Column Triggers form. Numbered buffers already appear in this list.

The restrictions on buffer names are virtually identical to those of customized triggers. The only difference is that, of course, no key strings may be used.

Nesting INCLUDE Commands

The #INCLUDE command can be nested. That is, one trigger can include another, which in turn includes a third trigger (and so on).

Example: The PRE-INSERT trigger of the TRANSTRIG form includes many buffers from the same form. (The TRANSTRIG form is a special form that only contains triggers included in other forms.)

Advantages of the Wildcards

Wildcards ($ and @) are very useful when including one trigger in another. This is because the wildcard has a relative meaning, which depends upon the form in which the trigger is activated.

Example: :$$.DOC in the PRE-INSERT trigger of the Received Items form refers to :DOCUMENTS_P.DOC, whereas in the PRE-INSERT trigger of the Shipped Items form, it refers to :DOCUMENTS_D.DOC.

Error and Warning Messages

Triggers inherit not only all SQL statements from the included trigger (or buffer), but also their accompanying error and warning messages. The scope of the messages is all the triggers written for this form.

Checking Trigger Usage

Caution must be exercised when revising a trigger that is included in other triggers, as any changes in the former will obviously affect the latter. You can view any triggers that include the current trigger in the Use of Trigger sub-level form of Form Column Triggers and of Row & Form Triggers.

More on Triggers