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Overview

The ussd language syntax is declarative and intuitive. we’ve broken it into 5 easy parts to help us grasp it.

  • Actions
  • Variables
  • Control flows
  • Effects
  • Modules

Actions

Section titled “Actions”

Actions are used to define things that display on the users screen. They’re mostly defined ending with a colon.

We currently have entry:, finish:, prompt:, list:, <number>:

<number>: is used for defining options.
example
1: Send money
2: Check balance

More on Actions Learn about all the available actions in the ussd syntax.

Variables

Section titled “Variables”

A variable can be used to store some information throughout a session.

Example of a variable that takes users name and age then prints them at the end of the flow

source.ussd
entry: Profile updator
prompt: What's should we call you? -> name
  finish: You're called {name}.

As seen above, we kept the user’s name in a name variable and then used that variable in the final action.

More on Variables Learn more about how variables work.

Control flows

Section titled “Control flows”

These are used to control the path of a flow based on the state of a variable. We currenly support just the if-else control flow

Example USSD application that has two branching flows based on whether you entered a value or not.

source.ussd
entry: Age picker
  prompt: What's your age? -> age
    if age
      finish: You're {age} years old.
    else
      finish: You didn't enter your age.
More on Control flows Learn more on how to manage the flow in a ussd application

Effects

Section titled “Effects”

Effects allow us to call external logic or APIs. This is actually where your business logic lives outside the definition of your USSD flow but can then be called from the flow.

Example USSD application that allows a user in when they’re above the age of 18.

source.ussd
entry: Age picker
  prompt: What's your age? -> age
  @checkAge(age) -> isValid
    if isValid
      finish: Welcome to our service.
    else
      finish: You're too young to be here
More on Effects Learn all about effects. How to call external APIs and write business logic

Modules

Section titled “Modules”

Modules are used to make a piece of USSD flow reusable.

An example is to wrap the code for asking user information into a module that can be reused.

More on Modules Learn all about effects. How to call external APIs and write business logic