设计模式中的聚合和组合

聚合：整体与部分之前的弱关系，部分不会随着整体生命周期的结束而结束。eg：电脑（整体）与 鼠标（部分）

has -a 关系，父类包含子类，但子类可以独立存在

组合：整体与部分之间的强关系，部分随着整体生命周期的结束而结束（部分不能脱离整体单独存在）。 eg: 鸟（整体）与 翅膀（部分）

part-of 关系，父类拥有子类，子类不能独立与父类存在

一组关联关系是聚合还是组合，要根据实际业务来看，两个类，在不同的场景中可以有不同的关联关系

代码案例

（1）聚合关系

namespace TestCore
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Name testName = new Name() { ChineseName = "小明" };
            Address testAddress = new Address() { HomeAddress ="地球" };
            Student testStudent = new Student(testName, testAddress);
            Console.WriteLine("更改前的名称:" + testStudent._name.ChineseName);
            Console.WriteLine("更改前的地址：" + testStudent._address.HomeAddress);
            Console.WriteLine("开始更改 testName 与 testAddress 的值-------------");
            testName.ChineseName = "小明(更改后)";
            testAddress.HomeAddress = "地球（更改后）";
            Console.WriteLine("更改后的名称:" + testStudent._name.ChineseName);
            Console.WriteLine("更改后的地址：" + testStudent._address.HomeAddress);
        }
    }

    public class Student {
        public Name _name;
        public Address _address;
        /*
         此处Name和Address与Student是聚合关系，子类Name与Address的生命周期不会随着Student的生命周期结束而结束
        且此处Name与Address在Student中出现是以地址的形式，并未开辟新的存储空间，而是将现有的对象的地址传递给了Student类的属性，当外界name对象与address对象发生变化时，Student的这两个属性会随之变换
         */
        public Student(Name name, Address address)
        {
            this._name = name;
            this._address = address;
        }
    }
    public class Name{
        public string ChineseName { get; set; }
    }

    public class Address { 
        public string HomeAddress { get; set; }
    }
}

运行结果：

（2）组合关系

namespace TestCore
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Name testName = new Name() { ChineseName = "小明" };
            Address testAddress = new Address() { HomeAddress ="地球" };
            Student testStudent = new Student(testName, testAddress);
            Console.WriteLine("更改前的名称:" + testStudent._name.ChineseName);
            Console.WriteLine("更改前的地址：" + testStudent._address.HomeAddress);
            Console.WriteLine("开始更改 testName 与 testAddress 的值-------------");
            testName.ChineseName = "小明(更改后)";
            testAddress.HomeAddress = "地球（更改后）";
            Console.WriteLine("更改后的名称:" + testStudent._name.ChineseName);
            Console.WriteLine("更改后的地址：" + testStudent._address.HomeAddress);
        }
    }

    public class Student {
        public Name _name;
        public Address _address;
        /*
         此处Name和Address与Student是组合关系，Name与Address在Student中开辟了新的存储空间，传给Student的不是一个地址，而是一个独立的对象，这个对象和外部的testName、testAddress已经没有关系，不会随之改变
         */
        public Student(Name name, Address address)
        {
            this._name = new Name() { ChineseName = name.ChineseName};
            this._address = new Address() { HomeAddress = address.HomeAddress};
        }
    }
    public class Name{
        public string ChineseName { get; set; }
    }

    public class Address { 
        public string HomeAddress { get; set; }
    }
}

运行结果：