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设计模式-原型模式

发表于 更新于 分类于 Valine：
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原型模式是用于创建重复的对象，同时又能保证性能, 当直接创建对象的代价比较大时例如，一个对象需要在一个高代价的数据库操作之后被创建。我们可以缓存该对象，在下一个请求时返回它的克隆，在需要的时候更新数据库，以此来减少数据库调用。

示例

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//普通实现
class Resume
{
    private string name;
    private string sex;
    private string age;
    private string timeArea;
    private string compart;

    public Resume(string name)
    {
        this.name = name;
    }
    public void SetPersonalInfo(string sex, string age)
    {
        this.sex = sex;
        this.age = age;
    }
    public void SetWorkExperience(string timeArea, string company)
    {
        this.timeArea = timeArea;
        this.company = company;
    }
    public void Display()
    {
        Console.WriteLine("{0} {1} {2}", name, sex, age);
        Console.WriteLine("工作经历: {0} {1}", timeArea, company);
    }
}
//Client---需要多次创建对象
Resume a = new Resume("小a");
a.SetPersonalInfo("男", "21");
a.SetWorkExperience("2021-2022", "a公司");
Resume b = new Resume("小a");
b.SetPersonalInfo("男", "21");
b.SetWorkExperience("2022-2023", "b公司");

a.Display();
b.Display();
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//原型模式
class Resume : ICloneable
{
    private string name;
    private string sex;
    private string age;
    private string timeArea;
    private string compart;

    public Resume(string name)
    {
        this.name = name;
    }
    public void SetPersonalInfo(string sex, string age)
    {
        this.sex = sex;
        this.age = age;
    }
    public void SetWorkExperience(string timeArea, string company)
    {
        this.timeArea = timeArea;
        this.company = company;
    }
    public void Display()
    {
        Console.WriteLine("{0} {1} {2}", name, sex, age);
        Console.WriteLine("工作经历: {0} {1}", timeArea, company);
    }
    public Object Clone()
    {
        //浅拷贝--值类型:逐位复制, 引用类型只复制引用(指向同一对象)
        return (Object)this.MemberwiseClone();
    }
}
//Client
Resume a = new Resume("小a");
a.SetPersonalInfo("男", "21");
a.SetWorkExperience("2021-2022", "a公司");
Resume b = (Resume)a.Clone();
b.SetWorkExperience("2022-2023", "b公司");

a.Display();
b.Display();

浅拷贝存在的问题: 对于引用类型只是拷贝其引用, 创建多个对象后引用类型都指向同一对象

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class WorkExperence
{
    private string workDate;
    public string WorkDate
    {
        get{return workDate;}
        set{workDate = value;}
    }
    public string company;
}
class Resume : ICloneable
{
    private string name;
    private string sex;
    private string age;
    private WorkExperence work;

    public Resume(string name)
    {
        this.name = name;
        work = new WorkExperence();
    }
    public void SetPersonalInfo(string sex, string age)
    {
        this.sex = sex;
        this.age = age;
    }
    public void SetWorkExperience(string timeArea, string company)
    {
        work.WorkDate = timeArea;
        work.Company = company;
    }
    public void Display()
    {
        Console.WriteLine("{0} {1} {2}", name, sex, age);
        Console.WriteLine("工作经历: {0} {1}", timeArea, company);
    }
    public Object Clone()
    {
        //浅拷贝--值类型:逐位复制, 引用类型只复制引用(指向同一对象)
        return (Object)this.MemberwiseClone();
    }
}
//Client
Resume a = new Resume("小a");
a.SetPersonalInfo("男", "21");
a.SetWorkExperience("2021-2022", "a公司");
Resume b = (Resume)a.Clone();
b.SetWorkExperience("2022-2023", "b公司");//---引用类型重新赋值会覆盖原有值

a.Display();
b.Display();

深拷贝需要考虑要深入到多少层

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//深拷贝
class WorkExperence : ICloneable
{
    private string workDate;
    public string WorkDate
    {
        get{return workDate;}
        set{workDate = value;}
    }
    public string company;
    public Object Clone()
    {
        //浅拷贝--值类型:逐位复制, 引用类型只复制引用(指向同一对象)
        return (Object)this.MemberwiseClone();
    }
}
class Resume : ICloneable
{
    private string name;
    private string sex;
    private string age;
    private WorkExperence work;

    public Resume(string name)
    {
        this.name = name;
        work = new WorkExperence();
    }
    public Resume(WorkExperence work)
    {
        this.work = (WorkExperence)work.Clone();
    }
    public void SetPersonalInfo(string sex, string age)
    {
        this.sex = sex;
        this.age = age;
    }
    public void SetWorkExperience(string timeArea, string company)
    {
        work.WorkDate = timeArea;
        work.Company = company;
    }
    public void Display()
    {
        Console.WriteLine("{0} {1} {2}", name, sex, age);
        Console.WriteLine("工作经历: {0} {1}", timeArea, company);
    }
    public Object Clone()
    {
        //深拷贝
        Resume obj = new Resume(this.work);
        obj.name = this.name;
        obj.sex = this.sex;
        obj.age = this.age;
        return obj;
    }
}
//Client
Resume a = new Resume("小a");
a.SetPersonalInfo("男", "21");
a.SetWorkExperience("2021-2022", "a公司");
Resume b = (Resume)a.Clone();
b.SetWorkExperience("2022-2023", "b公司");

a.Display();
b.Display();