原理

這種類(lèi)型的設(shè)計(jì)模式屬于創(chuàng)建型模式，它提供了一種創(chuàng)建對(duì)象的最佳方式。
在工廠(chǎng)模式中，我們?cè)趧?chuàng)建對(duì)象時(shí)不會(huì)對(duì)客戶(hù)端暴露創(chuàng)建邏輯，并且是通過(guò)使用一個(gè)共同的接口來(lái)指向新創(chuàng)建的對(duì)象。

意圖

定義一個(gè)創(chuàng)建對(duì)象的接口，讓其子類(lèi)自己決定實(shí)例化哪一個(gè)工廠(chǎng)類(lèi)，工廠(chǎng)模式使其創(chuàng)建過(guò)程延遲到子類(lèi)進(jìn)行。

主要解決

主要解決接口選擇的問(wèn)題。

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 簡(jiǎn)單工廠(chǎng)模式
{
    class Program
    {
        static void Main(string[] args)
        {
            Operation oper;
            oper = OperationFactory.createOperate("+");
            oper.NumberA = 1;
            oper.NumberB = 2;
            double result = oper.GetResult();
            Console.Write("result: " + result);
            Console.ReadKey();
        }
    }
}

Operation.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 簡(jiǎn)單工廠(chǎng)模式
{
    //簡(jiǎn)單工廠(chǎng)類(lèi)
    class OperationFactory
    {
        public static Operation createOperate(string operate)
        {
            Operation oper = null;
            switch (operate)
            {
                case "+":   oper = new OperationAdd();
                    break;
                case "-":   oper = new OperationSub();
                    break;
                case "*":   oper = new OperationMul();
                    break;
                case "/":   oper = new OperationDiv();
                    break;
            }
            return oper;
        }
    }

    //運(yùn)算類(lèi)
    class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;

        public double NumberA {
            get { return _numberA; }
            set { _numberA = value; }
        }
        public double NumberB
        {
            get { return _numberB; }
            set { _numberB = value; }
        }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }
    //加法類(lèi)
    class OperationAdd : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }
    //減法類(lèi)
    class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }
    //乘法類(lèi)
    class OperationMul : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA * NumberB;
            return result;
        }
    }
    //除法類(lèi)
    class OperationDiv : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (NumberB == 0) {
                throw new Exception("除數(shù)不能為0."); 
            }
            result = NumberA / NumberB;
            return result;
        }
    }

}