Logic and Conditions

Sometimes building your logic you may want to execute some steps conditionally.

A good example is greeting a complete new user of your Alexa Skill / Google Action. You may want to onboard a new user a little bit, explain how your skill or action works. To do that you can use the concept of conditional steps.

Consider the following example:

- name: First Time User Welcome Step
  # The actions of this step will only be executed
  # when returning_user variable DOES NOT exist yet
  when: 'returning_user is not defined'
    - sendText: "Let's welcome our first time user! "
    # Setting a context variable returning_user to true
    - set: 'returning_user = true'
    - sendText: 'Do you want to continue?'
    - getInput:
    yes_next: Start of the Scenario Logic
    no_thanks: Exit
    AMAZON.CancelIntent: Exit
    AMAZON.StopIntent: Exit
    AMAZON.HelpIntent: Help
    # The counter-part of WHEN is ELSE
    # The execution will continue to the step Returning User Welcome Step
    # When the variable returning_user DOES exist
    else: Returning User Welcome Step

- name: Returning User Welcome Step
  # The actions inside this step will execute
  # only when the variable returning_user equals true
  when: 'returning_user == true'
    - sendText: "Let's welcome our returning user! "
    else: Start of the Scenario Logic

- name: Start of the Scenario Logic
    - sendText: 'Let us start with the scenario logic right here!'
  next: Exit

We tried to put the basic decision making logic in the comments inside of this scenario. Here is just a quick overview of what is happening in the text form:

  1. When the user starts the skill / action the first step First Time User Welcome Step is executed
  2. Before any of the actions INSIDE of this steps are executed, the condition after the when statement is evaluated. In this case - the condition is the existence of the variable that we evaluate with the is not syntax.
  • WHEN the condition is true and variable returning_user doesn’t exist - everything inside of the actions section is executed:
    • The user hears the text “Let’s welcome our first time user!”
    • We set the the variable returning_user to true
    • We ask a user ‘Do you want to continue?’
    • We are waiting for the user’s response with getInput
  • ELSE everything inside of the actions section is skipped and BotTalk jumps directly to the else built-in intent. Which is linked to the Returning User Welcome Step
  • In the Returning User Welcome Step we demonstrate that everything you put inside of the when condition will be interpreted as a TWIG expressions. This step also demonstrates another important concept. If the expression inside of the when statement will be evaluated as false, the whole actions section will be skipped - and BotTalk will move to the next section.

Written by Andrey Esaulov on 12 March 2019

Updated on 12 March 2019