Working in Twig, I had to add classes to a pre-existing array.  Whilst I've grown used to the patterns in PHP, these cannot be applied in Twig.  Instead I had to merge the new array elements. Non associative arrays Working from a base level, I'll begin as if the original array hasn't been set.  The merge filter expects as first argument an array whose content will be merged with the assigned variable: {% set myArray = [] %} {% set myArray = myArray|merge(['tw-flex-inline'])...

During the process of building the app, there are warnings about the code.  It's good practice to remove all warnings before you submit your apps to the App Store so there's a few steps you can follow to silence these warnings: Navigate the the Project Settings page below; Select the drop down menu next to Devices; Change from Universal to iPhone; then Run your app again and the warnings should disappear.