I can't go into a lot of detail at the moment, but if you're open to using something non-Moose based (at least for inflating the nested data structures), Venus can do all of this for you via the "Venus::Role::Coerciable" role. If you want to stick with Moose you could try reverse engineering "Venus::Role::Coerciable" and using it with your Moose classes. Here's how to do it in Venus:

package JsonData;
 
use Venus::Class;
 
with 'Venus::Role::Coercible';
 
attr 'icon';
attr 'url';
attr 'datetime';
attr 'subject_html';
 
sub coerce {
  {
    ...,
    icon => 'JsonData/Icon',
    url => 'Mojo/URL',
    datetime => 'Mojo/Date',
    subject_html => 'Mojo/DOM',
    ...,
  }
}

package JsonData::Icon;
 
use Venus::Class;
 
with 'Venus::Role::Coercible';
 
attr 'url';
attr 'comment';
attr 'picid';
attr 'keywords';
 
sub coerce {
  {
    ...,
    url => 'Mojo/URL',
    ...,
  }
}

1;
[download]

Venus::Class

Venus::Role::Coercible