jbuilder with Condition if .present?

Question

if presenter.present?
    @presenter = presenter 
end
json.extract! @presenter.shop, :id, :name
json.schedule @presenter.formated_schedule

and i have this error

NameError:
     #   undefined local variable or method `presenter' for #<ActionView::Base:0x0000000000d6b0>

I tried in one line and it still doesn't work

@presenter = presenter if presenter.present?
json.extract! @presenter.shop, :id, :name
json.schedule @presenter.formated_schedule