C#中使用委托、接口、匿名方法、泛型委托实现加减乘除算法
使用C#实现加减乘除算法经常被用作新手练习。本篇来分别体验通过委托、接口、匿名方法、泛型委托来实现。
使用委托实现
加减乘除拥有相同的参数个数、类型和返回类型，首先想到了使用委托实现。
//创建一个委托
public delegate decimal MathOperation(decimal left, decimal right);
//创建方法参数和返回结果符合委托的定义
public static decimal Add(decimal left, decimal right)
{
return left + right;
}
public static decimal Subtract(decimal left, decimal right)
{
return left - right;
}
public static decimal Multiply(decimal left, decimal right)
{
return left * right;
}
public static decimal Divide(decimal left, decimal right)
{
return left / right;
}
//返回委托类型
private static MathOperation GetOperation(char oper)
{
switch(oper)
{
case '+': return Add;
case '-': return Subtract;
case '*': return Multiply;
case '/': return Divide;
}
throw new NotSupportedException("");
}
//封装一个方法用来把操作数和符号考虑进来,返回委托类型
private static decimal Eval(string expr)
{
var elements = expr.Split(new []{' '}, 3);
var left = Decimal.Parse(elements[0]);
var right = Decimal.Parse(elements[1]);
var ope = elements[2][0];
return GetOperation(op)(left, right);
}
void Main()
{
Console.WriteLine(Eval("1 3 +"));
}
使用接口实现
以上，委托用在了方法层面。如果在类层面，也可用接口封装加减乘除的共性。
public interface IMathOperation
{
decimal Compute(decimal left, decimal right);
}
public class AddOperation : IMathOperation
{
decimal Compute(decimal left, decimal right)
{
return left + right;
}
}
public class SubtractOperation : IMathOperation
{
decimal Compute(decimal left,, decimal right)
{
return left - right;
}
}
public class MultiplyOperation : IMathOperation
{
decimal Compute(decimal left, decimal right)
{
return left * right;
}
}
public class DivideOperation : IMathOperation
{
decimal Compute(decimal left, decimal right)
{
return left/right;
}
}
//获取接口类型
private static IMathOperation GetOperation(char oper)
{
switch(oper)
{
case '+': return new AddOperation();
case '-': return new SubtractOperation();
case '*': return new MultiplyOperation();
case '/': return new DivideOperation();
}
throw new NotSupportedException("");
}
使用匿名方法
委托还可以结合匿名方法一起使用。
public delegate decimal MathOperation(decimal left, decimal right);
private static MathOperation GetOperation(char oper)
{
switch(oper)
{
case '+': return delgate(decimal left, decimal right) {return left + right;};
case '-': return delgate(decimal left, decimal right) {return left - right;};
case '*': return delgate(decimal left, decimal right) {return left * right;};
case '/': return delgate(decimal left, decimal right) {return left / right;};
}
throw new NotSupportedException("");
}
泛型委托
而用泛型委托实现更简洁。
private static Func<decimal, decimal, decimal> GetOperation(char oper)
{
switch(oper)
{
case '+': return (left, right) => left + right;
case '-': return (left, right) => left - right;
case '*': return (left, right) => left * right;
case '/': return (left, right) => left / right;
}
throw new NotSupportedExcepton("");
}
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