there is one (type)

This construct tests whether a collection contains one and only one object of a given type.

Purpose

You use this construct to determine whether the specified collection contains one and only one occurrence of a particular object.

Syntax

there is one <type> [in <list>] [where <test>,]

Description

Use the in clause to apply the test to a specific collection of objects. Use one or more optional where clauses to filter the objects to be counted with one or more conditions.

This construct can be used only in the if part of a rule.

Example

The following condition tests if there is one Gold customer in the list of customers.

if
   there is one customer in the customers of bank
      where the category of this customer is Gold
then...