def declare_logic():
Rule.sum(derive=Customer.Balance, as_sum_of=Order.AmountOwed)
Rule.formula(derive=Order.AmountOwed,
as_expression=lambda row: row.AmountTotal - row.AmountPaid)
Rule.sum(derive=Order.AmountPaid,
as_sum_of=PaymentAllocation.AmountAllocated)
Rule.formula(
derive=PaymentAllocation.AmountAllocated,
as_expression=lambda row: min(Decimal(row.Payment.AmountUnAllocated),
Decimal(row.Order.AmountOwed)))
Rule.early_row_event(on_class=Payment, calling=allocate_payment)
"""
def load_rules(self):
def my_early_event(row, old_row, logic_row):
logic_row.log("early event for *all* tables - good breakpoint, time/date stamping, etc")
def check_balance(row: Customer, old_row, logic_row) -> bool:
"""
Not used... illustrate function alternative (e.g., more complex if/else logic)
specify rule with `calling=check_balance` (instead of as_condition)
"""
return row.Balance <= row.CreditLimit
def compute_amount(row: OrderDetail, old_row, logic_row):
return row.UnitPrice * row.Quantity
Rule.formula(derive="OrderDetail.Amount", calling=compute_amount)
Rule.formula(derive="OrderDetail.Amount", calling=lambda Customer: Customer.Quantity * Customer.UnitPrice)
Rule.early_row_event(on_class="*", calling=my_early_event) # just for debug
Rule.constraint(validate="Customer", calling=check_balance,
error_msg="balance ({row.Balance}) exceeds credit ({row.CreditLimit})")