Create Declare Expression rules to automatically calculate values in your
application. Declare Expression rules take advantage of values that exist in your system to
calculate values of target properties. As a result, you increase automation of calculations in
For example, in an online shopping order, an application can
automatically calculate the tax value based on prices of the items and the information that tax
equals a specific percentage of the item price. By implementing Declare Expression rules, the
application recalculates the tax value every time the customer updates the shopping
What to do next: Define a declare expression. For more information, see Defining expressions in Declare Expression rules.
- In the header of Dev Studio, click .
- In the Target Property field, enter a property that you want to
calculate, preceding the property name with a period.For example: For the TaxValue property, enter
- Optional: To restrict search for the result of the declare expression to a specific page, in the
Page Context field, enter a data page that stores available
results.For example: To situate a target property on the .pyItemNames()
embedded page, enter .Invoices.pyOrders().pyItems().pyItemNames().
Leave the parentheses blank because a declare expression applies to all elements on a
- In the Context section, select the application layer in which you
want to store the rule.
- In the Apply to field, enter the class that stores the target
Note: When you create a declare expression, you can first provide the class, and then
provide the target property in the Target Property field. If you
select a class first, the system limits the available target properties to the
properties that the selected class stores.
- In the Add to ruleset field, enter a ruleset to store the
- Click Create and open.