Clean Code_Note4_Remove Duplicated Code

 

Remove Duplicated Code

以下範例是有重複感覺的程式段落例子

Before

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using System; namespace CleanUpMethods { public class RemoveDuplicatedCode { private decimal _belowTaxSalaryAmount; private decimal _taxPercentage; public RemoveDuplicatedCode(decimal belowTaxSalaryAmount, decimal taxPercentage) { _belowTaxSalaryAmount = belowTaxSalaryAmount; _taxPercentage = taxPercentage; } public decimal CheckAndCalculate(decimal higherSalaryAmount, decimal grossSalaryAmount) { if (grossSalaryAmount < 0) { throw new ArgumentException("Provided salary amount is not correct."); } if (higherSalaryAmount < 0) { throw new ArgumentException("Provided salary amount is not correct."); } return CalculateNetAmount(grossSalaryAmount, higherSalaryAmount); } private decimal CalculateNetAmount(decimal grossSalaryAmount, decimal higherSalaryAmount) { if (_belowTaxSalaryAmount == 0 || _taxPercentage == 0) { return grossSalaryAmount; } decimal taxSum = 0m; if (grossSalaryAmount <= _belowTaxSalaryAmount) { return grossSalaryAmount; } decimal tax = (grossSalaryAmount - _belowTaxSalaryAmount) * (_taxPercentage / 100); taxSum += tax; decimal taxableSalary = grossSalaryAmount; if (taxableSalary > higherSalaryAmount) { taxableSalary = higherSalaryAmount; } tax = (taxableSalary - _belowTaxSalaryAmount) * (_taxPercentage / 100); taxSum += tax; return grossSalaryAmount - taxSum; } } }

可以看到這部分主要throw的exeption訊息都一樣差別只在前面的if判斷參數數值傳入有差

抽離後

CalculateNetAmount方法重複部分

也是差別在於第一個參數其他計算公式一樣。

抽離後

完整的After

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using System; namespace CleanUpMethods { public class RemoveDuplicatedCode { private decimal _belowTaxSalaryAmount; private decimal _taxPercentage; public RemoveDuplicatedCode(decimal belowTaxSalaryAmount, decimal taxPercentage) { _belowTaxSalaryAmount = belowTaxSalaryAmount; _taxPercentage = taxPercentage; } public decimal CheckAndCalculate(decimal higherSalaryAmount, decimal grossSalaryAmount) { CheckAmountIsGreaterThenZero(grossSalaryAmount); CheckAmountIsGreaterThenZero(higherSalaryAmount); return CalculateNetAmount(grossSalaryAmount, higherSalaryAmount); } private static void CheckAmountIsGreaterThenZero(decimal salaryAmount) { if (salaryAmount < 0) { throw new ArgumentException("Provided salary amount is not correct."); } } private decimal CalculateNetAmount(decimal grossSalaryAmount, decimal higherSalaryAmount) { if (_belowTaxSalaryAmount == 0 || _taxPercentage == 0) { return grossSalaryAmount; } decimal taxSum = 0m; if (grossSalaryAmount <= _belowTaxSalaryAmount) { return grossSalaryAmount; } decimal tax = CalculateTaxAmount(grossSalaryAmount); taxSum += tax; decimal taxableSalary = grossSalaryAmount; if (taxableSalary > higherSalaryAmount) { taxableSalary = higherSalaryAmount; } tax = CalculateTaxAmount(taxableSalary); taxSum += tax; return grossSalaryAmount - taxSum; } private decimal CalculateTaxAmount(decimal salaryAmount) { return (salaryAmount - _belowTaxSalaryAmount) * (_taxPercentage / 100); } } }