herderWageThisMonthOnly method
Implementation
num herderWageThisMonthOnly(int herderId, DateTime datePreviousMonth) =>
where((t) => t.status)
.where((t) => t.contactId == herderId)
.where((t) => t.date.year == datePreviousMonth.year)
.where((t) => t.date.month == datePreviousMonth.month)
.where((t) => t.ticketType == TicketType.wage)
.fold(0.0, (prev, e) => prev + e.received);