Refactoring Day 13 : Extract Method Object
Today's refactoring comes from Martin Fowlers list of refactorings. You can find his original article here with a brief description.
This is a more infrequent refactoring that I see myself using but it comes in handy at times. When trying to apply an Extract Method refactoring, and multiple methods are needing to be introduced, it is sometimes gets ugly because of multiple local variables that are being used within a method. Because of this reason, it is better to introduce an Extract Method Object refactoring and to segregate the logic required to perform the task.
1: public class OrderLineItem 2: { 3: public decimal Price { get; private set; } 4: } 5: 6: public class Order 7: { 8: private IList<OrderLineItem> OrderLineItems { get; set; } 9: private IList<decimal> Discounts { get; set; } 10: private decimal Tax { get; set; } 11: 12: public decimal Calculate() 13: { 14: decimal subTotal = 0m; 15: 16: // Total up line items 17: foreach (OrderLineItem lineItem in OrderLineItems) 18: { 19: subTotal += lineItem.Price; 20: } 21: 22: // Subtract Discounts 23: foreach (decimal discount in Discounts) 24: subTotal -= discount; 25: 26: // Calculate Tax 27: decimal tax = subTotal * Tax; 28: 29: // Calculate GrandTotal 30: decimal grandTotal = subTotal + tax; 31: 32: return grandTotal; 33: } 34: }
This entails passing a reference to the class that will be returning the computation to a new object that has the multiple methods via the constructor, or passing the individual parameters to the constructor of the method object. I will be showing the former here.
1: public class OrderLineItem 2: { 3: public decimal Price { get; private set;} 4: } 5: 6: public class Order 7: { 8: public IEnumerable<OrderLineItem> OrderLineItems { get; private set;} 9: public IEnumerable<decimal> Discounts { get; private set; } 10: public decimal Tax { get; private set; }
31 Days of Refactoring Sean Chambers 25
11: 12: public decimal Calculate() 13: { 14: return new OrderCalculator(this).Calculate(); 15: } 16: } 17: 18: public class OrderCalculator 19: { 20: private decimal SubTotal { get; set;} 21: private IEnumerable<OrderLineItem> OrderLineItems { get; set; } 22: private IEnumerable<decimal> Discounts { get; set; } 23: private decimal Tax { get; set; } 24: 25: public OrderCalculator(Order order) 26: { 27: OrderLineItems = order.OrderLineItems; 28: Discounts = order.Discounts; 29: Tax = order.Tax; 30: } 31: 32: public decimal Calculate() 33: { 34: CalculateSubTotal(); 35: 36: SubtractDiscounts(); 37: 38: CalculateTax(); 39: 40: return SubTotal; 41: } 42: 43: private void CalculateSubTotal() 44: { 45: // Total up line items 46: foreach (OrderLineItem lineItem in OrderLineItems) 47: SubTotal += lineItem.Price; 48: } 49: 50: private void SubtractDiscounts() 51: { 52: // Subtract Discounts 53: foreach (decimal discount in Discounts) 54: SubTotal -= discount; 55: } 56: 57: private void CalculateTax() 58: { 59: // Calculate Tax 60: SubTotal += SubTotal * Tax; 61: } 62: }
Refactoring Day 13 : Extract Method Object
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转载自blog.csdn.net/lifeqiuzhi521/article/details/81193017
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