Question

I’m trying to find a design pattern or a best practice, or some other solution for a problem with keeping back versions of business logic within my application. Specifically, I am looking to find a way to determine which logic was used to issue an insurance policy.

I currently have code which looks like this:

public double FixedDeductibleSurchageAmount()
{
    double percent = FixedDeductibleSurchargePercent();
    double base_premium = CollisionPremium() + TheftPremium();
    return (base_premium * percent);
}

I am needing to make a change to the business logic so that this function looks more like:

public double FixedDeductibleSurchageAmount()
{
    double percent = FixedDeductibleSurchargePercent();
    double base_premium = CollisionPremium() + TheftPremium() + MedicalPremium();
    return (base_premium * percent);
}

Where I run into trouble is that existing policies should rate with the previous logic. Is there a design pattern for this? If not, are there any good ways to implement it?

Answer 1

Strategy pattern sounds most applicable. Probably you’d need a factory method or some such that takes in a date to return the appropriate strategy.