With the help of parameters, you can run the same workflow for different source files or time periods, parametrize expressions, and perform "what-if" analysis. Parameters can be used in action properties, in expressions, and in database queries. Parameters are also used to arrange iterations (described futher in the tutorial).

A parameter has a name and a value. Anywhere where a parameter is referenced by its name, its value is used instead. Parameters allow replacing hardcoded constants or properties in workflows with values that can be easily changed by user.

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Parameter Editor

Before a parameter can be used it must be declared (created) first. Creating, editing, renaming and deleting parameters is done in the Parameter Editor. To open the Parameter Editor, select "Edit parameters" in the menu "Main", or press F6.

There are two types of parameters: input parameters, and calculated parameters. Input parameters are entered by a user and can be of serveral types. Besides general purpose parameters, there are special parameter types such as "Date" or "File path". The special parameter types have a helper button that invokes the file browser dialog or a calendar and can be more convenient for specifying file names or dates.

A calculated parameter is a parameter which value is calculated using an expression that can consist of arithmetical operators, functions and even other parameters. Parameter evaluation happens in a context that is outside of tables therefore referencing a field name in a calculated parameter makes no sense and is not allowed.

Hint: A calculated parameter can refer to other calculated parameters.

The parameters of a module are accessible from all actions in the module and are constant (immutable). They do not change during project execution. A parameter has the same value for any action. Actions inside a module don't and can't change a parameter of the same module.

See example: Character count

Using parameters in action properties

In actions, parameters can be used to specify the values of some properties. Typically, action properties such as file names, folder paths, numeric constants or dates can be specified with a parameter. Action properties that can be specified with a parameter are easy to notice — they have a black arrow next to it (see screenshot below).

See example: Character count

Using parameters in expressions

In expressions, parameters work as constants. They can be used in arithmetic operations and functions. Parameter names in expressions should be wrapped in curly brackets. A parameter name can consist of any characters except curly brackets. For convenience, the Expression Editor has a clickable list of parameters.

See example: Character count

Using parameters in database queries

Project parameters can be used in visual database queries as well. Click the black arrow to replace a condition value with a parameter (see screenshot below).

Project parameters can be inserted into a custom SQL query or WHERE clause. Before executing the query, every parameter name in curly braces is replaced with its current value (the curly braces are not inserted). Put quotes around curly braces when a text value is expected to be inserted into the query.

See example: Formula 1

Advanced topics

Advanced mode of Parameter Editor

The Parameter Editor can be switched into the advanced mode that enables additional features:

  • Advanced parameter types: "Fixed list", "Checkbox", and "Multiple choice"
  • Annotations
  • Labels (user-friendly labels that are shown instead of parameter names)
  • Parameter validation rules (restrictions for parameter values)
  • Copying/pasting parameters

Parameters and Auto-run mode

When Auto-run mode is on, changing a parameter automatically triggers re-calculation of all actions that use the parameter to specify an action property, in an expression, or in a database query. First, this ensures consistency of calculations and makes sure that all action results are calculated using the same parameter values. Second, it is convenient for "what-if" scenarios — by changing parameters you can automatically re-run calculations and evaluate various outcomes.

Parameter validation

Parameters can have validation rules that check parameter values for correctness. Each validation rule is a condition that evaluates either to TRUE or to FALSE. If it's FALSE, validation fails.

The validation rules are evaluated before project execution. Therefore, if a validation rule failed, no action will be executed. The rules are a great mechanism to ensure that a workflow is only executed with correct parameter values.

Parameter validation rules can be configured in the advanced mode of the Parameter Editor.

Read next: Calling modules / projects