An expression is a text string that defines the syntax to be evaluated by the expression evaluator. The expression input can comprise of numbers, strings, access strings, symbols, and operators. Once you attach an item type with an expression defined, the corresponding value of the expression will display in the element's Properties dialog.
You can access this feature from the Property Definition section in the Item Types Dialog by selecting an Item's property definition.
- String - "Pipe"
- Integer - 1
- Double - 6.84
- Symbol - you can use symbols to supply values to expression evaluators. Symbols can be from an instance via an access string, defined value, or an application defined method. Following are a few examples:
- Operators -
Use last Valid Value
Note: Item Type libraries created using Expressions in Update 13 will not be compatible with Units and Use last valid value fields in Update 15. To overcome this, you must use the key-in Itemtype Upgrade All.
This key-in will upgrade item types from older libraries and will make them compatible with Units and Use last valid value fields.