More about Map Values
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Map value rules can be updated as needed to reflect changing business conditions, without the need to ask a skilled developer to modify complex activities or other rules.
If you have in advance an Excel spreadsheet in XLS file format that contains useful starting information for a map value, you can incorporate (or "harvest") the XLS file and the information it contains directly into the new rule.
Both rows and columns contain a Type field (set on the Headers tab). The system makes comparisons according to the data type you recorded on the Headers tab, converting both the input and the conditions to the specified data type.
At runtime, the system evaluates row conditions first from top to bottom, until one is found to be true. It then evaluates column conditions for that row, left to right, until one is found to be true. It returns the value computed from that matrix cell.
You can reference map values in the following places:
Call keyword in a cell.If a map value is evaluated through a decision shape on a flow, or one of the two methods noted above, the input value or values may be literal constants or may be property references, recorded in the flow or in the method parameters.
However, if a map value is evaluated by a Call from a cell in another map value, the evaluation always uses the Input Property on the Header tab. Nothing in the Call can override this source.
When a Declare Expression rule has Result of map value for the Set Property To field, special processing occurs at runtime when a property referenced in the decision table is not present on the clipboard. Ordinarily such decision rules fail with an error message; in this case the Default value is returned instead. For details, see PDN article Troubleshooting: declarative expression does not execute when a decision rule provides no return value.
The Pega 7 Platform does not limit the number of nodes in a map value. However, as a best practice to avoid slow performance when updating the form and also avoid the Java 64KB code maximum, limit your map value rules to no more than 300 to 500 rows.
Click Actions > View Java to view the generated Java of a rule. You can use the Java code to debug your application or to examine how rules are implemented.
Through directed inheritance, the immediate parent of the Rule-Obj-MapValue class is the Rule-Declare- class. However, despite the class structure, this rule type does not produce forward or backward chaining. Technically, it is not a declarative rule type.