Function MongoCollection.findOne
Queries the collection for existing documents.
auto findOne(R, T, U)
(
T query,
U returnFieldSelector,
QueryFlags flags = QueryFlags
);
auto findOne(R, T)
(
T query
);
Returns
By default, a Bson value of the matching document is returned, or Bson(null)
when no document matched. For types R that are not Bson, the returned value is either
of type R, or of type , if R is not a reference/pointer type.
Throws
Exception if a DB communication error or a query error occured.