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List Tools

List tools access and sometimes modify the contents of a list variable. List variables are like regular variables, except that they can hold more than one value. For example, a variable of type ListofString can contain two or more string values. List variables are created using the InsertAtHead and InsertAtTail tools.

List variables allow you to hold multiple values of a specific type. For example, a list variable of a string type could contain many string values. A list variable can be declared for each of the following data types: String, Integer, Boolean, Database, DateTime, DBConnection, and Numeric. There is no limit to the number of elements in a list.

For each element in a list variable is assigned a place number. The first place number is always zero, the second is one, the third is two, and so on. The first element in a list is called a Head. Therefore, the Head of a list is always at place number 0. The end of a list is called a Tail. The place number for a tail is always the number of the last element in a list. Therefore, the place number of the tail may change as elements are added or removed from a list.

You might want to use a list variable to store multiple items retrieved from multiple fetches to a database. For example, if you have a handler that allows callers to retrieve information on all financial transactions that have occurred for a specific account over the past five days, you could have a step that fetches information on all transactions and stores them in a list variable.

List variables may be created for the following data types: