The Expression component allows defining an expression in function of its inputs. The result of evaluating the expression will be returned as output. The expression can also use constants and functions provided byITPilot.
This component accepts zero or more values, zero or more pages, zero or more records, and zero or more record lists.
This component returns the result of evaluating the expression.
If any “Hidden” field on the inputs is used to build the expression, the wizard will prompt to ask whether the resulting expression must be hidden too or not.
Variable initialization Expression component shows part of a process that uses the expression component to initialize a variable (e.g. CURRENTPAGE) to 1. Creation of a constant value in the Expressions Editor shows that the initialization is as simple as assigning an integer constant to the expression value.
Following this initialization, another Expression component can be used within a loop (either a Loop, a Repeat, or an Iterator component) to act as a counter, in this case a pages counter (see Use of an Expression component as a pages counter):
Below is explained how to use the Expression editor to define the expression (see Using a function in the Expressions Editor).
Using the Expressions Editor¶
The expressions editor is shown in Using a function in the Expressions Editor. The expression is built by manually typing in the “Expression Value” box. This editing box provides some features to assist when the expression is being typed: syntax highlighting and text completing.
Syntax highlighting: the errors in the expression are highlighted in red, and by hovering the mouse over the erroneous elements a description of the error will be provided as a tooltip. Also, different colors are used to highlight constants, functions and variables.
Text completing: a popup menu for text completing can be invoked by typing Ctrl+Space; it also appears after the expression is changed. This menu shows a list of elements that can be inserted in the current position, as input variables or functions (both built-in and custom). The items can be selected by clicking with the mouse or navigating the list with the up and down arrows and pressing Enter.
The list of elements will only show the items that match the current prefix. For example, after writing a “c” character and opening the text completing menu, only the functions whose names start with “c” will be suggested.
Also, the expected types are taken into account, depending on the place where the menu is open. If the menu is open inside a function, the list will only show the items with a type compatible with the type of the function parameter where the cursor is placed. For example, when completing parameters of the function concat, only variables of type string will appear, and only functions whose return type is string.
The functions that are in the text completing list include the core functions and the custom functions that are installed in the environment.
Creation of a constant value in the Expressions Editor shows an example in which a constant value is created and Using a function in the Expressions Editor shows an example in which an expression is used as a counter.