改善代码设计 —— 优化物件之间的特性(Moving Features Between Objects)

1. Move Method (函数搬家)

解释:

冲动前:

class EmployeeSalary
{
private double baseSalary = 15000.0;

public double Salary(Employee employee)
{
return baseSalary + 10000 / employee.Level;
}
// other method with baseSalary
}
class Employee
{
public int Level { get; set; }
}

冲动后:

class EmployeeSalary
{
private double baseSalary = 15000.0;

public double Salary(Employee employee)
{
return employee.Salary(baseSalary);
}
// other method with baseSalary
}
class Employee
{
public int Level { get; set; }
public double Salary(double baseSalary)
{
return baseSalary + 10000 / Level;
}
}

2. Move Field (值域搬家)

解释:

冲动前:

class EmployeeSalary
{
private double baseSalary = 15000.0;

public double Salary()
{
double salary = baseSalary;
//do some compution with salary
return salary;
}
}

冲动后:

class EmployeeSalary
{
public double Salary(Employee employee)
{
double salary = employee.BaseSalary;
//do some compution with salary
return salary;
}
}
class Employee
{
public double BaseSalary { get; set; }
}

3. Extract Class (提炼类)

解释:

冲动前:

class Employee
{
public double BaseSalary { get; set; }
public double Level { get; set; }

public double Salary()
{
double salary = BaseSalary;
//do some complex compution with salary
return salary;
}
}

冲动后:

class EmployeeSalary
{
public double Salary(Employee employee)
{
double salary = employee.BaseSalary;
//do some complex compution with salary
return salary;
}
}
class Employee
{
public double BaseSalary { get; set; }
public double Level { get; set; }

public double Salary()
{
EmployeeSalary salary = new EmployeeSalary();
return salary.Salary(this);
}
}

4. Inline Class (将类内联)

解释:

5. Hide Delegate (隐藏委托关系)

解释:

冲动前:

class Department
{
public string Manger { get; set; }
}
class Employee
{
public Department Department { get; set; }
}

冲动后:

class Department
{
public string Manger { get; set; }
}
class Employee
{
private Department Department;

public string GetManger()
{
return Department.Manger;
}
}

6. Remove Middle Man (干掉中间人)

解释:

7. Introduce Foreign Method (引入外加函数)

解释:

Introduce Foreign Method 有很深的 C#3.0 中扩展方法的味道, 但扩展方法比 Introduce Foreign Method 好在: 扩展方法就好象是被扩展的那个类型自己的方法一样, 而 Introduce Foreign Method 的函数还需要传递这个类型的参数, 但其实编译器编译扩展方法后还是会把参数传进去的, 扩展方法只是一种语法糖.

它的主要目的是实现被调用的类中没有实现的功能, 注意在进行本项重构时, 如果引入一个外加函数, 这说明这个函数本应该在被调用的类中实现. 下面举一个简单到不能再简单的例子, 这个例子只是说明怎么使用 Introduce Foreign Method, 我并不是说 Int32类型就应该有一个 NextNum 的方法 , 并且实际中多数情况下这种重构用于引用类型

冲动前:

int num = 1;
//I want to get num's next
int nextNum = num + 1;

冲动后:

int num = 1;
int nextNum = NextNum(num);

private static int NextNum(int arg)
{
return arg + 1;
}

8. Introduce Local Extension (引入本地扩展)

解释: