Variables & Scopes

We use variables to store values that can be used throughout the lifetime of a session. Every variable can only be used in the scope in which it was delcared.

Variable types

The USSD language supports 4 primitive types for variables

• Strings
• Numbers
• Booleans
• Lists

How to create a variable

We provide 3 ways of creating or getting values into variables.

1. Defining a Global Variable

Using the define keyword at the top of your source, you can define a variable with a string content

2. Return Value from an Effect

The return value from an effect call can hold variables of the types String, Number, Boolean or a List. Do identify a variable as holding a list value, we have to wrap it in a square bracket. eg. [variableName]

2.1 Marking an Effect Variable as a List

When a variable coming from an effect is wrapped in square brackets like [cars], it tells the compiler this variable cars contains a list. Note: the compiler will allow you to only use a list variable with the list: action.

3. An Action that takes user input into a variable

We have 2 actions that can take user input and store them into a variable which are the prompt: action and the list: action.

The prompt action takes in a string input and stores it into a variable. illustrated below

The list action shows the user a list and asks them to pick an item, two variables are then populated with the user’s pick to hold the id and view of their pick. illustrated below

on line 3, the list action renders a list of cars to the user and waits for the user to select one of them. The selection of the user is then used to populate the two variables on the right. The id and view of what the user selected.