How to set field type in transformer

[robert0770]

my date field is text type... 'addDate' => $offer->getAddDate() ? $offer->getAddDate()->format('c') : null, my price is text type.... 'price' => $offer->getPrice(), when i 'price' => (double) $offer->getPrice(),

i get error

Error in one or more bulk request actions: index: /app_offer/offer/621 caused mapper [price] cannot be changed from type [long] to [float]

how to set it like by yaml configuration?