C# |如何使用接口引用
在 C# 中，您可以创建一个接口类型的引用变量，或者换句话说，您可以创建一个接口引用变量。这类变量可以引用任何实现其接口的对象。接口引用变量只知道由其接口声明声明的方法。它不允许访问对象可能支持的任何其他变量或方法。当您使用父类引用来访问子类对象时，这个概念是相似的。
以下是说明接口引用概念的示例:
例 1:
// C# program to illustrate the
// concept of Interface References
using System;
// interface declaration
public interface Race {
// declaration of abstract methods of
// interface that will be implemented
// by the class which inherits the interface
void Speed(int s);
void Distance(int d);
}
// class implementing interface
public class Person1 : Race {
int sp1, di1;
// abstract method of
// Race interface
public void Speed(int p1s) {
sp1 = p1s;
Console.WriteLine("Speed Method implemented by Person1");
}
// abstract method of
// Race interface
public void Distance(int p1d) {
di1 = p1d;
Console.WriteLine("Distance Method implemented by Person1");
}
// method of class Person1
public void display1() {
Console.WriteLine("The Speed of 1st person is: "+sp1);
Console.WriteLine("The distance covered by 1st person is: "+di1);
}
}
// class implementing interface
public class Person2 : Race {
int sp2, di2;
// abstract method of
// Race interface
public void Speed(int p2s) {
sp2 = p2s;
Console.WriteLine("Speed Method implemented by Person2");
}
// abstract method of
// Race interface
public void Distance(int p2d) {
di2 = p2d;
Console.WriteLine("Distance Method implemented by Person2");
}
// method of class Person2
public void display2() {
Console.WriteLine("The Speed of 2nd person is: "+sp2);
Console.WriteLine("The distance covered by 2nd person is: "+di2);
}
}
// Driver Class
public class GFG {
// Main method
public static void Main(String []args) {
// creating an instance of Person1 class
Person1 obj1 = new Person1();
// creating an instance of Person2 class
Person2 obj2 = new Person2();
// creating an Reference
// of interface Race
Race r;
// ----- For Person1 Class ----------
// assigning Person1 object 'obj1'
// to interface Reference 'r'
r = obj1;
// Now you can access the abstract method
// of Race interface which are implemented
// by class Person1
r.Speed(10);
r.Distance(50);
// if you will try to call display1()
// method using 'r' it will give error
//r.display1();
// calling the display1()
// method of Person1 Class
obj1.display1();
// ----- For Person2 Class ----------
// assigning Person2 object 'obj2'
// to interface Reference 'r'
r = obj2;
// Now you can access the abstract method
// of Race interface which are implemented
// by class Person2
r.Speed(15);
r.Distance(45);
// if you will try to call display2()
// method using 'r' it will give error
//r.display2();
// calling the display1()
// method of Person1 Class
obj2.display2();
}
}
输出:
Speed Method implemented by Person1
Distance Method implemented by Person1
The Speed of 1st person is: 10
The distance covered by 1st person is: 50
Speed Method implemented by Person2
Distance Method implemented by Person2
The Speed of 2nd person is: 15
The distance covered by 2nd person is: 45
说明:在上面的例子中，我们有一个名为 Race 的接口，以及两个类 Person1 和 Person2 ，它们实现了接口的方法。 Person1 类有自己的方法名为 display1() ，类似的 Person2 类有自己的方法 display2() ，不能使用接口引用调用。为了调用使用接口引用的方法(这里 r 是接口引用)，你必须给它分配一个类对象。例如，如果您将 Person1 的对象 obj1 分配给 r ，即r = obj 1；然后调用 Person1 类实现的 Speed() 和 Distance() 方法。要调用 display1() 方法，必须使用 obj1。同样使用r = obj 2；我们正在调用 Person2 类的方法。
例 2:
// C# program to illustrate the
// concept of Interface References
using System;
// interface declaration
interface Vehicle {
// all are the abstract methods.
void changeGear(int a);
void speedUp(int a);
void applyBrakes(int a);
void printStates();
}
// class implements interface
class Bicycle : Vehicle {
int speed;
int gear;
// to change gear
public void changeGear(int newGear)
{
gear = newGear;
}
// to increase speed
public void speedUp(int increment)
{
speed = speed + increment;
}
// to decrease speed
public void applyBrakes(int decrement)
{
speed = speed - decrement;
}
public void printStates()
{
Console.WriteLine("speed: " + speed + " gear: " + gear);
}
}
// Driver Class
class GFG {
// Main Method
public static void Main(String[] args)
{
// creating an instance of Bicycle
Bicycle bicycle = new Bicycle();
// Creating interface references
Vehicle obj;
// assigning Bicycle object 'bicycle'
// to interface Reference 'obj'
obj = bicycle;
// calling the abstract methods
// implemented by class Bicycle
obj.changeGear(4);
obj.speedUp(5);
obj.applyBrakes(2);
Console.WriteLine("Bicycle Present State:");
// calling the method of class Bicycle
obj.printStates();
}
}
输出:
Bicycle Present State:
speed: 3 gear: 4
说明:在上例中，Vehicle 是一个接口，Bicycle 类实现了这个接口。这里 obj 被声明为 Main()方法中对 Vehicle 接口的引用。现在这个 obj 用来指代自行车类的目标自行车。
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