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设计模式

工厂模式

创建方法（Create Methods）

调用构造函数进行封装，隐藏创建细节体现代码意图，增强代码可维护性

例如我们有一个部门，部门中有一个工种程序员

public class Programmer { } // 程序员类
public class Department // 部门类
{// 这是一个创建方法(也可以写成静态)public Programmer CreateEmployee(){return new Programmer();}
}

调用创建方法

Department department = new Department();
Programmer programmer = department.CreateEmployee();

简单工厂（Simple Factory）

现在部门增加了一个工种，设计师工种，那么我们使用简单工厂模式，通过给定参数的不同来创建不同的对象

// 工种枚举
public enum EEmployeeType
{Programmer,Designer
}
public class Employee {} // 工种父类
public class Programmer : Employee { } // 程序员类
public class Designer : Employee { } // 设计师类
public class Department // 部门类
{// 用简单工厂实现创建方法public Employee CreateEmployee(EEmployeeType employeeType){Employee employee = new Employee();switch (employeeType){case EEmployeeType.Programmer:employee = new Programmer();break;case EEmployeeType.Designer:employee = new Designer();break;default:throw new System.ArgumentException("Invalid employee type");}return employee;}
}

调用创建方法

Department department = new Department();
Employee programmer = department.CreateEmployee(EEmployeeType.Programmer);
Employee designer = department.CreateEmployee(EEmployeeType.Designer);

工厂方法（Method Factory）

1. 创建子类工厂

如果现在又又需要增加工种，那么在简单工厂的基础上我们只能通过修改CreateEmployee方法的实现细节，不符合违背了开闭原则（对象应该对扩展开放，修改封闭），那么我们使用工厂方法，将对象的创建方法下发到子类工厂中

public abstract class Department // 父类工厂
{public abstract Employee CreateEmployee();
}public class ITDepartment : Department // 程序员工厂
{public override Employee CreateEmployee(){return new Programmer();}
}public class UIDepartment : Department // 设计师工厂
{public override Employee CreateEmployee(){return new Designer();}
}

创建方法调用，通过使用不同的子类工厂来完成创建，这样扩展新工种时只需要创建类和子类工厂

ITDepartment itDepartment = new ITDepartment();
itDepartment.CreateEmployee();
UIDepartment uiDepartment = new UIDepartment();
uiDepartment.CreateEmployee();

2.创建模板方法

如果这个时候需要对每个新创建的员工都实现一个注册账户的方法，可以发现从创建对象到注册的业务执行是固定的，但是每一个接口所对应的具体实现不同

加入注册方法

public abstract class Employee // 工种父类
{public abstract string RegisterAccount(); // 注册方法
}public class Programmer : Employee // 程序员类
{public override string RegisterAccount(){return "IT" + Random.Range(0, 100);}}public class Designer : Employee // 设计师类
{public override string RegisterAccount(){return "UI" + Random.Range(100, 200);}
} 

实现父类工厂中的模板方法

public abstract class Department // 部门抽象类
{protected abstract Employee CreateEmployee();public Employee Onboard(){employee = CreateEmployee(); // 具体实现通过子类employee.RegisterAccount();return employee;}
}

创建方法调用

ITDepartment itDepartment = new ITDepartment();
itDepartment.Onboard();UIDepartment uiDepartment = new UIDepartment();
uiDepartment.Onboard();

抽象工厂（Abstract Factroy）

加入程序员有程序项目，设计师有设计项目，使用抽象工厂

public abstract class Project // 项目父类
{public abstract void AssignTo(); // 项目接口
}public class ITProject : Project // 程序项目类
{public override void AssignTo(){Debug.Log("Assign an IT to project");}
}public class UIProject : Project // 设计师项目类
{public override void AssignTo(){Debug.Log("Assign an UI to project");}
}

重构部门抽象类，加入项目类

public abstract class Department // 部门抽象类
{public abstract Employee CreateEmployee();public abstract Project CreateProject();
}
public class ITDepartment : Department
{public override Employee CreateEmployee(){return new Programmer();}public override Project CreateProject(){return new ITProject();}}public class UIDepartment : Department
{public override Employee CreateEmployee(){return new Designer();}public override Project CreateProject(){return new UIProject();}
}

创建工厂管理类，实现一对多的关系，例如一个程序员部门，可以有多个项目，多个员工

// 工厂管理类
public class DepartManager
{private Department _department;public List<Project> _projects;public Dictionary<string, Employee> _employees;public DepartManager(Department department){_department = department;}public Project CreateProject(){if (_projects == null) _projects = new List<Project>();Project project = _department.CreateProject();_projects.Add(project);return project;}public string CreateEmployee(){if (_employees == null) _employees = new Dictionary<string, Employee>();Employee employee = _department.CreateEmployee();string accountNo = employee.RegisterAccount();_employees.Add(accountNo, employee);return accountNo;}
}

方法调用

DepartManager itDepManager = new DepartManager(new ITDepartment());
itDepManager.CreateProject();
itDepManager.CreateEmployee();DepartManager uiDepManager = new DepartManager(new UIDepartment());
itDepManager.CreateProject();
itDepManager.CreateEmployee();

策略模式