For some reason it's not that easy. It's not seeing the attributes as a normal (what i call) ruby path (object.attribute).
f.project_task.start_date shows this error
undefined method `project_task' for #<ActionView::Helpers::FormBuilder:0x32e19b0>
project_task.start_date shows this
undefined method `start_date' for nil:NilClass
f.start_date shows this
undefined method `start_date' for #<ActionView::Helpers::FormBuilder:0x2eda844>
the f object is this class
I'll take a look at the stackoverflow page, thanks.