[英]Polymorphism without using the virtual keyword
顯然,使用虛擬和替代是正常情況,但是這個電信示例是否有價值?
public class Pipe
{
// whole bunch of protected member variables such as bandwidth, latency, download limit
// etc,
public int GetCost()
{
// work out cost based on above
}
}
public class BigFatPipe : Pipe
{
public BigFatPipe()
{
// sets up the member variables one way
}
}
public class CheapestPossiblePipe: Pipe
{
public CheapestPossiblePipe()
{
// sets up the member variables another way
}
}
那你可能會打電話
PrintPrice(new BigFatPipe())
PrintPrice(new CheapestPossiblePipe())
public void PrintPrice(Pipe pipe)
{
int a = pipe.GetCost();
....
}
您會得到兩個不同的答案。 這不是最有用的示例,但是它有用嗎?
這篇文章對確切的多態性進行了有用的討論。
我認為大多數定義都沒有明確指出對象必須具有多態的虛函數-是的,我認為您的示例很重要。
構造函數重載是實現靜態多態性的公認方法。 盡管這並不是真正的構造函數重載,但已經很接近了。 所以是的,我稱之為多態性。
這種模式確實有效,但是引入一堆類會使用戶無用的困惑:他們會想知道這些類的不同之處。
一些工廠方法可以完成相同的工作,並且更易於理解和維護:
public class Pipe
{
// whole bunch of private member variables such as bandwidth, latency, download limit
// etc,
public int GetCost()
{
// work out cost based on above
}
public static Pipe MakeBigFatPipe()
{
var result = new Pipe();
// sets up the member variables one way
return result;
}
public static Pipe MakeCheapestPossiblePipe()
{
var result = new Pipe();
// sets up the member variables another way
return result;
}
}
如果我是你,我將使用以下方法:
public interface IGetCost
{
int GetCost();
}
public class Pipe : IGetCost
{
public int GetCost(){}
}
public class BigFatPipe : IGetCost
{
//aggregation
private readonly Pipe _pipe;
public BigFatPipe(Pipe pipe)
{
_pipe = pipe;
}
public int GetCost() { }
}
public class CheapestPossiblePipe : IGetCost
{
private readonly Pipe _pipe;
public CheapestPossiblePipe(Pipe pipe)
{
_pipe = pipe;
}
public int GetCost() { }
}
public static void PrintPrice(IGetCost obj)
{
int cost = obj.GetCost();
Console.WriteLine(cost);
}
static void Main(string[] args)
{
IGetCost p;
p = new Pipe();
PrintPrice(p);
p = new BigFatPipe();
PrintPrice(p);
p = new CheapestPossiblePipe();
PrintPrice(p);
}
我還需要說的是,有兩種不同的東西-多態和重載
多態性
public class foo
{
public virtual void foo1{/*....*/}
}
public class fooA : foo
{
public override void foo1{/*....*/}
}
public class fooB : foo
{
public new void foo1{/*....*/}
}
public class fooC : foo
{
//new is the default modifier
public void foo1{/*....*/}
}
超載
public class foo{
public int foo1{/*....*/}
public int foo1(int a){/*....*/}
public int foo1(string a){/*....*/}
public int foo1(int a, string b){/*....*/}
}
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