Variables in Expressions

You often need to create variables when constructing view models, particularly as the complexity of the model grows or as you use more advanced operators such as Iterator. WorkSpace Data Federation provides a JavaScript object named variables, which lets you store any variables you wish to use across multiple operators.

Refer to any variables using the following syntax to guarantee their uniqueness across your model:

variables.<operatorInstanceName>.<variableName>

The operatorInstanceName referred to should be the name of the operator where the variable is declared.

You can either enter variable names directly in your expressions, or you can use the expressions menu to enter the name of any downstream variable.

Note: Variables that you declare in a given operator are only available (are only in scope) to operators that are upstream in the flow from that operator. Operators that are downstream from that operator or on a different branch of the flow cannot access your variable. If you need to use a variable across multiple branches, for example, you can declare it in your model’s .jsi file.

In the expressions that you enter, it’s OK to update variables defined downstream, as long as they’re not control variables. However:

Do not try to update variables that are defined upstream—you may see unexpected results if you change a variable outside of the operator that creates the variable. (All downstream variables appear in the expressions menu.)
If you use a control variable—a counter introduced in and maintained by an Iterator operator, for example—don’t update the control variable inside any operator other than the one that introduces it.

Valid Variable Types for Expressions
All values in the variables structure must be of one of the types listed here. Note that global parameters, while defined using SQL types, are accessed in your expressions using the corresponding Java types, according to JDBC conventions.

Parent topic: Develop

Parent topic: Adding an Operator

Related concepts

Operators in View Models

Access to Columns from Incoming Result Sets

Access to Global Parameters

Performance of Sort-Based Operators in View Models