how can I access "petName" of each document and store in dropdownbutton

I need to retrieve data from Firestore to get "petName" of each document and then I used in dropdownbutton.
But problem is that I am not getting any field . I received only documents. As also show in output dropdownbutton.

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>Solution :

you are using document you have to specify what exactly like as in your case you want petName so use that instead of using the whole document.

try:

snap.data()['petName']