[SOLVED] When "absend" condition in Alexa APL

When "absend" condition in Alexa APL

I have a data structure which can optionally hold a value if so I want to display it. In my example it is the field "quantity". However if it is set both blocks will be shown instead of just one. Where is the error?

{
  "when": "${data.quantity === undefined}",
  "type": "Text",
  "text": "for ${data.price}",
  "style": "textStyleDetails"
},
{
  "when": "${data.quantity >= 0}",
  "type": "Text",
  "text": "${data.quantity}x for ${data.price}",
  "style": "textStyleDetails"
},

I also tried the conditions:

data.quantity == 'undefined'
!data.quantity
(typeOf data.quantity) === 'undefined'

None of them work.

Solution

Try using ${data.quantity == null} Null is a recognized constant in the APL data binding syntax: https://developer.amazon.com/docs/alexa-presentation-language/apl-data-binding-syntax.html#null. Also the '===' operator is not supported in APL.