Created: 2008-11-03 09:40
Updated: 2015-11-05 00:41
License: mit



A plugin for Adhearsion to add form functionality and flow, similar to VoiceXML style forms.

By Adam Meehan (adam.meehan@gmail.com, http://duckpunching.com/)

Released under the MIT license.


The plugin adds form features to Adhearsion components to quickly and semantically setup data input for your voice application. You define a form and form fields in which to collect data and setup callbacks to instruct the caller, give feedback, confirm input and validate input.


sudo gem install voice_form

At the bottom your projects startup.rb file put

require 'voice_form'


Here is the Adhearsion example Simon game redone using voice_form:

class SimonGame
  include VoiceForm

  voice_form do
    setup do
      @number = ''

    field(:attempt, :attempts => 1) do
      prompt :play => :current_number, :bargein => false, :timeout => 2

      setup do
        @number << random_number

      validate do
        @attempt == @number

      success do
        call.play 'good'

      failure do
        call.play %W[#{@number.length-1} times wrong-try-again-smarty]
        @number = ''


  def random_number

  def current_number

That covers most of the functionality, and hopefully it makes sense pretty much straight away.

To start the form, in your dialplan:

For Adhearsion 0.7.999

general {
  simon_game = new_simon_game

For Adhearsion 0.8.x

general {

You don't have to start the form from the dialplan, but it makes it simple. You could start it from within a component method.

All callback blocks (setup, validate, timeout etc.) are evaluated in the component scope so you can use component methods and instance variables in them and they will work. You don't have to define any callbacks if the field is straight forward and only depends on its length.

For a more complete example see the examples folder.



The flow of the form works like a stack. So each field and do_block are executed in order until the end of the form is reached. You can jump around the stack by using form.goto :field_name which will move the stack pointer to the field after the current field is completed and move forward through the form stack from that point, regardless whether a field has already been completed.

You can also use form.restart to start the form over from the beginning.

The form setup block is only run once and is not executed again, even with a form.restart.


This defines the field with the name given to collect on the form. The field method can be used in a voice_form or on its own inside a component method.

The options available are:

  • :length - the number of digits to accept
  • :min_length - minimum number of digits to accept
  • :max_length - maximum number of digits to accept
  • :attempts - number of tries to get a valid input
  • :call - the method name for the call context if other than 'call'. Used for standalone fields not in a form.

All fields defined get an accessor method defined of the same name in the component class. This means you can access its value using the instance variable or the accessor method inside any of the field callbacks and in other fields on a form.

The prompt and reprompt methods are a wrapper around the input command. And as such is always interruptable or you can bargein when you want to starting keying numbers. You pass in a hash of options to control the prompt such as:

  • :play - play one or more sound files
  • :speak - play TTS text (needs my Adhearsion hack for speak in input command)
  • :timeout - number of seconds to wait for input. Default is 5.
  • :repeats - number of attempts to use this prompt until the next one is used
  • :bargein - whether to allow caller to interrupt prompt. Default is true.

The length expected for the input is taken from the options passed to the field method.

You can only use one of :play or :speak.

There can only be one prompt but you can have multiple reprompts. When you add a reprompt it changes what the prompt is if there is input the first time or the input is invalid.


The available callbacks that can be defined for a field are as follows

  • setup
  • timeout
  • validate
  • invalid
  • confirm
  • success
  • failure

Each of them takes a block which is executed as a specific point in the process of getting form input. All of them are optional. The block for a callback is evaluated in the scope of the component so any instance variables and component methods are available to use including the call context.

The details of each callback are as follows


This is run once only for a field if defined before any prompts


This is run if no input is received or input is not of a valid length as defined by length or min_length field options.


This is run after input of a valid length. The validate block is where you put validation logic of the value just input by the user. The block should return true if the value is valid or false otherwise. If the validate callback returns false then the invalid callback will be called next.


The invalid callback is called if validate block returns false.


The confirm callback is called after the input has been validated. The confirm callback is a little different from the others. Idea is that you return either an array or string of the audio files or TTS text, respectively, you want to play as the prompt for confirming the value entered. The confirm block also takes a few options:

  • :accept - the number to press to accept the field value entered. Default is 1.
  • :reject - the number to press the reject the field value entered and try again. Default is 2.
  • :attempts - the number of attempts to try to get a confirmation response. Default is 3
  • :timeout - the number of seconds to wait for input after the confirmation response. Default is 3.

The value returned from the block should form the complete list of audio files or TTS text to prompt the user including the values to accept of reject the value.

For example, in a field called my_field:

confirm(:accept => 1, :reject => 2, :attempts => 3) do
  ['you-entered', as_digits(@my_field), 'is-this-correct', 'press-1-accept-2-try-again'].flatten

The above will play the array of audio files as the prompt for confirmation.

confirm(:accept => 1, :reject => 2, :attempts => 3) do
  "You entered #{@my_field}. Is this correct? Press 1 to accept or 2 try again."

The above will speak the string as the prompt for confirmation.

If no valid input is entered for the confirmation then another you will be reprompted to enter the field value.

Form methods

Inside a callback you have the form method available. The returns the instance of the current form. The form has some methods to allow you to perform form actions which manipulate the form stack. These actions are as follows:


Inside any callback you can use the goto command to designate which field the form should run after the current field. Normally the form will progress through the fields in the order defined, but a goto with shift the current form position to the field name pass to it like so:

failure do
  form.goto :other_field_name

The form continues from the field in the goto run each subsequent field in order. If the goto field is above the current field then the current field will be executed again when it is reached in the stack. If the goto field is below the current field then form will continue there, skipping whatever fields may lie between the current and the goto field.


The form may be restarted from the start at any point with form.restart. This will go back to the top of the form and proceed through each field again. The form setup will not be run again however.


To exit the form after the current field is complete just execute form.exit. The application will then be returned to where the form was started, be it a dialplan or another form.


Adam Meehan (adam.meehan@gmail.com, http://duckpunching.com/)

Also thanks to Jay Phillips et al. for the brilliant work on Adhearsion (http://adhearsion.com)

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