Csharp/C Sharp/Class Interface/Class Access Modifiers
Содержание
Demonstrate protected
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// Demonstrate protected.
using System;
class B {
protected int i, j; // private to B, but accessible by D
public void set(int a, int b) {
i = a;
j = b;
}
public void show() {
Console.WriteLine(i + " " + j);
}
}
class D : B {
int k; // private
// D can access B"s i and j
public void setk() {
k = i * j;
}
public void showk() {
Console.WriteLine(k);
}
}
public class ProtectedDemo {
public static void Main() {
D ob = new D();
ob.set(2, 3); // OK, known to D
ob.show(); // OK, known to D
ob.setk(); // OK, part of D
ob.showk(); // OK, part of D
}
}
</source>
illustrates member accessibility
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example7_3.cs illustrates member accessibility
- /
using System;
// declare the MotorVehicle class class MotorVehicle {
// declare the fields
private string make;
protected string model;
// define a constructor
public MotorVehicle(string make, string model)
{
this.make = make;
this.model = model;
}
// define the Start() method (may be overridden in a
// derived class)
public virtual void Start()
{
TurnStarterMotor();
System.Console.WriteLine("Vehicle started");
}
// define the TurnStarterMotor() method
private void TurnStarterMotor()
{
System.Console.WriteLine("Turning starter motor...");
}
}
// declare the Car class (derived from MotorVehicle) class Car : MotorVehicle {
// define a constructor
public Car(string make, string model) :
base(make, model)
{
// do nothing
}
// override the base class Start() method
public override void Start()
{
Console.WriteLine("Starting " + model); // model accessible
base.Start(); // calls the Start() method in the base class
// Console.WriteLine("make = " + make); // make is not accessible
}
}
public class Example7_3 {
public static void Main()
{
// create a Car object and call the object"s Accelerate() method
Car myCar = new Car("Toyota", "MR2");
myCar.Start();
// make and model are not accessible, so the following two lines
// are commented out
// Console.WriteLine("myCar.make = " + myCar.make);
// Console.WriteLine("myCar.model = " + myCar.model);
}
}
</source>
illustrates member hiding
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example7_4.cs illustrates member hiding
- /
using System;
// declare the MotorVehicle class class MotorVehicle {
// declare the fields
public string make;
public string model;
// define a constructor
public MotorVehicle(string make, string model)
{
Console.WriteLine("In MotorVehicle constructor");
this.make = make;
this.model = model;
Console.WriteLine("this.make = " + this.make);
Console.WriteLine("this.model = " + this.model);
}
// define the DisplayModel() method
public void DisplayModel()
{
Console.WriteLine("In MotorVehicle DisplayModel() method");
Console.WriteLine("model = " + model);
}
}
// declare the Car class (derived from MotorVehicle) class Car : MotorVehicle {
// hide the base class model field
public new string model;
// define a constructor
public Car(string make, string model) :
base(make, "Test")
{
Console.WriteLine("In Car constructor");
this.model = model;
Console.WriteLine("this.model = " + this.model);
}
// hide the base class DisplayModel() method
public new void DisplayModel()
{
Console.WriteLine("In Car DisplayModel() method");
Console.WriteLine("model = " + model);
base.DisplayModel(); // calls DisplayModel() in the base class
}
}
public class Example7_4 {
public static void Main()
{
// create a Car object
Console.WriteLine("Creating a Car object");
Car myCar = new Car("Toyota", "MR2");
Console.WriteLine("Back in Main() method");
Console.WriteLine("myCar.make = " + myCar.make);
Console.WriteLine("myCar.model = " + myCar.model);
// call the Car object"s DisplayModel() method
Console.WriteLine("Calling myCar.DisplayModel()");
myCar.DisplayModel();
}
}
</source>
Illustrates the use of various access modifiers
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example5_10.cs illustrates the use of various access modifiers
- /
// declare the Car class class Car {
// declare the fields
public string make;
protected internal string model;
internal string color;
protected int horsepower = 150;
private int yearBuilt;
// define the methods
public void SetYearBuilt(int yearBuilt)
{
this.yearBuilt = yearBuilt;
}
public int GetYearBuilt()
{
return yearBuilt;
}
public void Start()
{
System.Console.WriteLine("Starting car ...");
TurnStarterMotor();
System.Console.WriteLine("Car started");
}
private void TurnStarterMotor()
{
System.Console.WriteLine("Turning starter motor ...");
}
}
public class Example5_10 {
public static void Main()
{
// create a Car object
Car myCar = new Car();
// assign values to the Car object fields
myCar.make = "Toyota";
myCar.model = "MR2";
myCar.color = "black";
// myCar.horsepower = 200; // protected field not accessible
// myCar.yearBuilt = 1995; // private field not accessible
// call the SetYearBuilt() method to set the private yearBuilt field
myCar.SetYearBuilt(1995);
// display the values for the Car object fields
System.Console.WriteLine("myCar.make = " + myCar.make);
System.Console.WriteLine("myCar.model = " + myCar.model);
System.Console.WriteLine("myCar.color = " + myCar.color);
// call the GetYearBuilt() method to get the private yearBuilt field
System.Console.WriteLine("myCar.GetYearBuilt() = " + myCar.GetYearBuilt());
// call the Start() method
myCar.Start();
// myCar.TurnStarterMotor(); // private method not accessible
}
}
</source>
Member Accessibility
<source lang="csharp">
using System; public class MotorVehicle {
private string make;
protected string model;
public MotorVehicle(string make, string model) {
this.make = make;
this.model = model;
}
public virtual void Start() {
TurnStarterMotor();
System.Console.WriteLine("Vehicle started");
}
private void TurnStarterMotor() {
System.Console.WriteLine("Turning starter motor...");
}
} public class Product : MotorVehicle {
public Product(string make, string model) :
base(make, model) {
// do nothing
}
public override void Start() {
Console.WriteLine("Starting " + model);
base.Start();
}
} class MainClass {
public static void Main() {
Product myProduct = new Product("Toyota", "MR2");
myProduct.Start();
}
}
</source>
Member Hiding
<source lang="csharp">
using System; public class MotorVehicle {
public string make;
public string model;
public MotorVehicle(string make, string model) {
Console.WriteLine("In MotorVehicle constructor");
this.make = make;
this.model = model;
Console.WriteLine("this.make = " + this.make);
Console.WriteLine("this.model = " + this.model);
}
public void DisplayModel() {
Console.WriteLine("In MotorVehicle DisplayModel() method");
Console.WriteLine("model = " + model);
}
}
public class Product : MotorVehicle {
public new string model;
public Product(string make, string model) :
base(make, "Test") {
Console.WriteLine("In Product constructor");
this.model = model;
Console.WriteLine("this.model = " + this.model);
}
public new void DisplayModel() {
Console.WriteLine("In Product DisplayModel() method");
Console.WriteLine("model = " + model);
base.DisplayModel();
}
}
class MainClass {
public static void Main() {
Console.WriteLine("Creating a Product object");
Product myProduct = new Product("Toyota", "MR2");
Console.WriteLine("Back in Main() method");
Console.WriteLine("myProduct.make = " + myProduct.make);
Console.WriteLine("myProduct.model = " + myProduct.model);
Console.WriteLine("Calling myProduct.DisplayModel()");
myProduct.DisplayModel();
}
}
</source>
Public vs private access
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// Public vs private access.
using System;
class MyClass {
private int alpha; // private access explicitly specified
int beta; // private access by default
public int gamma; // public access
/* Methods to access alpha and beta. It is OK for a
member of a class to access a private member
of the same class.
*/
public void setAlpha(int a) {
alpha = a;
}
public int getAlpha() {
return alpha;
}
public void setBeta(int a) {
beta = a;
}
public int getBeta() {
return beta;
}
}
public class AccessDemo {
public static void Main() {
MyClass ob = new MyClass();
/* Access to alpha and beta is allowed only
through methods. */
ob.setAlpha(-99);
ob.setBeta(19);
Console.WriteLine("ob.alpha is " + ob.getAlpha());
Console.WriteLine("ob.beta is " + ob.getBeta());
// You cannot access alpha or beta like this:
// ob.alpha = 10; // Wrong! alpha is private! // ob.beta = 9; // Wrong! beta is private!
// It is OK to directly access gamma because it is public. ob.gamma = 99; }
}
</source>
Using Access Modifiers
<source lang="csharp">
public class Product {
public string make;
protected internal string model;
internal string color;
protected int horsepower = 150;
private int yearBuilt;
public void SetYearBuilt(int yearBuilt) {
this.yearBuilt = yearBuilt;
}
public int GetYearBuilt() {
return yearBuilt;
}
public void Start() {
System.Console.WriteLine("Starting Product ...");
TurnStarterMotor();
System.Console.WriteLine("Product started");
}
private void TurnStarterMotor() {
System.Console.WriteLine("Turning starter motor ...");
}
}
class MainClass {
public static void Main() {
Product myProduct = new Product();
myProduct.make = "Toyota";
myProduct.model = "MR2";
myProduct.color = "black";
myProduct.SetYearBuilt(1995);
System.Console.WriteLine("myProduct.make = " + myProduct.make);
System.Console.WriteLine("myProduct.model = " + myProduct.model);
System.Console.WriteLine("myProduct.color = " + myProduct.color);
System.Console.WriteLine("myProduct.GetYearBuilt() = " + myProduct.GetYearBuilt());
myProduct.Start();
}
}
</source>
