Unity实现设计模式------访问者模式
访问者模式(Vistor Pattern)是一种将数据结构和数据操作分离的设计模式。是指封装一些作用于某种数据结构中的各种元素的操作,它可以在不改变数据结构的前提下定义作用于这些元素的新操作。
访问者模式的基本思想是针对系统中拥有的某些固定类型的对象结构(元素),在其内部提供一个accept()方法用来接受访问者对象的访问。不同的访问者对同一元素的访问内容不同,所以使得相同的元素可以产生不同的元素结果。就是说不同的访问者访问同一个对象里面的不同属性,产生了不同的结果。
下面使用不同的访问者可以分别调整收入和假期
1.Element
csharp
abstract class Element
{
public abstract void Accept(IVisitor visitor);
}
2.Employee 职员
csharp
class Employee : Element
{
private string _name;
private double _income;
private int _vacationDays;
// Constructor
public Employee(string name, double income,
int vacationDays)
{
this._name = name;
this._income = income;
this._vacationDays = vacationDays;
}
// Gets or sets the name
public string Name
{
get { return _name; }
set { _name = value; }
}
// Gets or sets income
public double Income
{
get { return _income; }
set { _income = value; }
}
// Gets or sets number of vacation days
public int VacationDays
{
get { return _vacationDays; }
set { _vacationDays = value; }
}
public override void Accept(IVisitor visitor)
{
visitor.Visit(this);
}
}
3.IVisitor 访问者接口
csharp
interface IVisitor
{
void Visit(Element element);
}
4.IncomeVisitor 收入访问者
csharp
class IncomeVisitor : IVisitor
{
public void Visit(Element element)
{
Employee employee = element as Employee;
// Provide 10% pay raise
employee.Income *= 1.10;
Debug.Log(string.Format("{0} {1}'s new income: {2:C}",
employee.GetType().Name, employee.Name,
employee.Income));
}
}
5.VacationVisitor 假期访问者
csharp
class VacationVisitor : IVisitor
{
public void Visit(Element element)
{
Employee employee = element as Employee;
// Provide 3 extra vacation days
employee.VacationDays += 3;
Debug.Log(string.Format("{0} {1}'s new vacation days: {2}",
employee.GetType().Name, employee.Name,
employee.VacationDays));
}
}
6.Employees 职员集合
csharp
class Employees
{
private List<Employee> _employees = new List<Employee>();
public void Attach(Employee employee)
{
_employees.Add(employee);
}
public void Detach(Employee employee)
{
_employees.Remove(employee);
}
public void Accept(IVisitor visitor)
{
foreach (Employee e in _employees)
{
e.Accept(visitor);
}
}
}
7.不同的职员子类
csharp
class Clerk : Employee
{
// Constructor
public Clerk()
: base("Hank", 25000.0, 14)
{
}
}
class Director : Employee
{
// Constructor
public Director()
: base("Elly", 35000.0, 16)
{
}
}
class President : Employee
{
// Constructor
public President()
: base("Dick", 45000.0, 21)
{
}
}
8.测试
csharp
void Start()
{
// Setup employee collection
Employees e = new Employees();
e.Attach(new Clerk());
e.Attach(new Director());
e.Attach(new President());
// Employees are 'visited'
e.Accept(new IncomeVisitor());
e.Accept(new VacationVisitor());
}
就此为止23种设计模式中的11种行为模式介绍完毕!下面介绍其余的结构模式。