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外观

1. 简单工厂模式

约 322 字大约 1 分钟

2026-02-03

UML类图举例

实现一个加减乘除的运算器。只需要输入运算符号，工厂就实例化出合适的对象，通过多态，返回父类的方式实现了计算器的结果。如果我们需要增加各种复杂运算，比如平方根，立方根，自然对数，正弦余弦等，只要增加相应的运算子类就可以了。

PlantUML Diagram

抽象运算类：

public abstract class Operation
{
    public double NumberA { get; set; }
    public double NumberB { get; set; }

    public abstract double GetResult();
}

具体运算类：

public class OperationAdd : Operation
{
    public override double GetResult()
    {
        return NumberA + NumberB;
    }
}

public class OperationSub : Operation
{
    public override double GetResult()
    {
        return NumberA - NumberB;
    }
}

public class OperationMul : Operation
{
    public override double GetResult()
    {
        return NumberA * NumberB;
    }
}

public class OperationDiv : Operation
{
    public override double GetResult()
    {
        if (NumberB == 0)
            throw new DivideByZeroException("除数不能为0");

        return NumberA / NumberB;
    }
}

简单工厂类：

public 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;

            default:
                throw new ArgumentException("不支持的运算符");
        }

        return oper;
    }
}

客户端调用：

Operation oper = OperationFactory.CreateOperate("+");
oper.NumberA = 1;
oper.NumberB = 2;

double result = oper.GetResult();
Console.WriteLine(result);  // 输出 3