Flutter – Cast a String of a DocumentReference, to a DocumentReference

I encoded a Firestore DocumentReference inside a json object. Then I embed this string in a QR code. Then read the QR code with "mobile_scanner" package

"subscriber_document_reference" : "${subscriber.subscriberDocumentReference}"

Once I decode it, I get map with String key and also a String value. I want to change this String to an actual DocumentReference I can use.

naturally a direct cast fails with the exception:

 "type 'String' is not a subtype of type 'DocumentReference<Object?>' in type cast"

Edit: This is the encoding

 final data = ' {"subscriber_document_reference": "${subscriber.subscriberDocumentReference}" }';

final payload = json.encode(data);

The subscriber.subscriberDocumentReference is the correct type here: DocumentReference<Map<String, dynamic>>

I decode it

final String? displayValue = barcodes.barcodes.first.displayValue;  // mobile_scanner package code
final temp = json.decode(displayValue) as String;
final payload = json.decode(temp) as Map<String, dynamic>;

the value now is

"subscriber_document_reference": "DocumentReference<Map<String, dynamic>>(......)

note: ignore the decoding twice. I don’t know why it’s doing that, but since it works, it works.