using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace OverrideAndNew2
{
class Program
{
static void Main(string[] args)
{
// Declare objects of the derived classes and test which version
// of ShowDetails is run, base or derived.
TestCars1();
// Declare objects of the base class, instantiated with the
// derived classes, and repeat the tests.
TestCars2();
// Declare objects of the derived classes and call ShowDetails
// directly.
TestCars3();
// Declare objects of the base class, instantiated with the
// derived classes, and repeat the tests.
TestCars4();
}
public static void TestCars1()
{
System.Console.WriteLine("\nTestCars1");
System.Console.WriteLine("----------");
Car car1 = new Car();
car1.DescribeCar();
System.Console.WriteLine("----------");
// Notice the output from this test case. The new modifier is
// used in the definition of ShowDetails in the ConvertibleCar
// class.
ConvertibleCar car2 = new ConvertibleCar();
car2.DescribeCar();
System.Console.WriteLine("----------");
Minivan car3 = new Minivan();
car3.DescribeCar();
System.Console.WriteLine("----------");
}
// Output:
// TestCars1
// ----------
// Four wheels and an engine.
// Standard transportation.
// ----------
// Four wheels and an engine.
// Standard transportation.
// ----------
// Four wheels and an engine.
// Carries seven people.
// ----------
public static void TestCars2()
{
System.Console.WriteLine("\nTestCars2");
System.Console.WriteLine("----------");
var cars = new List<Car> { new Car(), new ConvertibleCar(),
new Minivan() };
foreach (var car in cars)
{
car.DescribeCar();
System.Console.WriteLine("----------");
}
}
// Output:
// TestCars2
// ----------
// Four wheels and an engine.
// Standard transportation.
// ----------
// Four wheels and an engine.
// Standard transportation.
// ----------
// Four wheels and an engine.
// Carries seven people.
// ----------
public static void TestCars3()
{
System.Console.WriteLine("\nTestCars3");
System.Console.WriteLine("----------");
ConvertibleCar car2 = new ConvertibleCar();
Minivan car3 = new Minivan();
car2.ShowDetails();
car3.ShowDetails();
}
// Output:
// TestCars3
// ----------
// A roof that opens up.
// Carries seven people.
public static void TestCars4()
{
System.Console.WriteLine("\nTestCars4");
System.Console.WriteLine("----------");
Car car2 = new ConvertibleCar();
Car car3 = new Minivan();
car2.ShowDetails();
car3.ShowDetails();
}
// Output:
// TestCars4
// ----------
// Standard transportation.
// Carries seven people.
}
// Define the base class, Car. The class defines two virtual methods,
// DescribeCar and ShowDetails. DescribeCar calls ShowDetails, and each derived
// class also defines a ShowDetails method. The example tests which version of
// ShowDetails is used, the base class method or the derived class method.
class Car
{
public virtual void DescribeCar()
{
System.Console.WriteLine("Four wheels and an engine.");
ShowDetails();
}
public virtual void ShowDetails()
{
System.Console.WriteLine("Standard transportation.");
}
}
// Define the derived classes.
// Class ConvertibleCar uses the new modifier to acknowledge that ShowDetails
// hides the base class method.
class ConvertibleCar : Car
{
public new void ShowDetails()
{
System.Console.WriteLine("A roof that opens up.");
}
}
// Class Minivan uses the override modifier to specify that ShowDetails
// extends the base class method.
class Minivan : Car
{
public override void ShowDetails()
{
System.Console.WriteLine("Carries seven people.");
}
}
}
請問， TestCars1() 中的car2.DescribeCar();
不是應該輸出為嗎？
// Four wheels and an engine.
// A roof that opens up.
為什么輸出的值為
// Four wheels and an engine.
// Standard transportation.
使用了new之后，不應該是子類屏蔽了父類的相同方法嗎？
爆炸了！！
uj5u.com熱心網友回復：
你用override關鍵字，才會有你想要的結果。用new表示，我用我的，你用你的。
不然，你想想，new能做到這種效果，那設計override有什么用？
uj5u.com熱心網友回復：
這種問題，我不喜歡用老外的東西解釋，new阿，overide啊，繞了來繞去，依舊不知道。我們用中國人都明白的事情一說你就明白了。
“偷梁換柱，李代桃僵，張冠李戴，指鹿為馬”
new，算“指鹿為馬”，鹿永遠不會成馬的，不過在特殊情況下“你說是馬那就是馬了”
同樣我們天朝人都知道，開會怎么說，酒桌上怎么說
開會或者酒桌上，你得說“行，沒問題，這事明天找我”，但回頭你明天找他就是“公事啊，公辦，你先去走個流程，我們在說后面的”
對，你這個new就這意思
公事 公事=new 酒桌上談的公事()
你想，現在到底輸出什么？是輸出“這事包在我身上”，還是輸出“公事啊還是公辦，我說的不算”
uj5u.com熱心網友回復：
公事 公事=new 酒桌上談的公事()酒桌上談的公事 公事=new 酒桌上談的公事()
區別一下這個，雖然是new的一個東西，但官字兩張口，說什么話取決與最前面的，而不是后面的。這是new的在程式里的意思
uj5u.com熱心網友回復：
精辟
uj5u.com熱心網友回復：
而且，new是隱含的，也就是說，也寫new，默認效果也還是new。父類和子類的同名方法，本來就是各用各的，除非你用了override。各用各的才是常態，override才是特殊轉載請註明出處，本文鏈接：https://www.uj5u.com/net/81383.html
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