Defining the expression
A validation rule is a boolean expression. PowerBuilder applies
the boolean expression to an entered value. If the expression returns “true”,
the value is accepted. Otherwise, the value is not accepted and
an ItemError event is triggered.
What expressions can contain
You can use any valid DataWindow expression in validation rules.
Validation rules can include most DataWindow expression functions. A DataWindow object that
will be used in PowerBuilder can also include user–defined
functions. DataWindow expression functions are displayed in the Functions list
and can be pasted into the definition.
For information about these functions, see the DataWindow
Reference.
Use the notation @placeholder (where placeholder is
any group of characters) to indicate the current column in the rule.
When you define a validation rule in the Database painter, PowerBuilder stores
it in the extended attribute system tables with the placeholder
name. At runtime, PowerBuilder substitutes the value of the column
for placeholder.
Pasting the placeholder
The @col can be easily used as the placeholder. A
button in the Paste area is labeled with @col. You can
click the button to paste the @col into the validation
rule.
An example
For example, to make sure that both Age and Salary are
greater than zero using a single validation rule, define the validation
rule as follows:
|
1 |
@col > 0 |
Then associate the validation rule with both the Age and Salary columns.
At runtime, PowerBuilder substitutes the appropriate values for the
column data when the rule is applied.