Classes and Objects. Andrew Cumming, SoC. Introduction to.net. Bill Buchanan, SoC. W.Buchanan (1)

Transcription

1 Classes and Objects Andrew Cumming, SoC Bill Buchanan, SoC W.Buchanan (1)

2 Course Outline 11-12am 12-1pm: 1-1:45pm 1:45-2pm:, Overview of.net Framework,.NET Components, C#. C# Language Elements Classes, Encapsulation, Object-Orientation, Classes, Sealed Classes, Interfaces, Abstract Classes. Certification Course Outline (Day 1 to 3) W.Buchanan (2)

3 Module 8 Classes and objects. Using encapsulation. Defining Object-Oriented Systems. Inheritance. Constructors. Sealed classes. Overriding classes. Introduction W.Buchanan (3)

4 Introduction to Object- Orientation (again!) W.Buchanan (4)

5 Some Cups W.Buchanan (5)

6 Parameter Cup 1 Cup 2 Cup3 Shape (Standard/Square/Mug) Standard Square Mug Colour (Red/Blue/Green) Blue Red Green Size (Small/Medium/Large) Small Large Small Transparency (0 to 100%) 100% 50% 25% Handle type (Small/Large) Small Small Large In object-orientation:a collection of parameters defines a class. Class for the cup is thus: Shape, Colour, Size, Transparency, HandleType. In object-orientation: Objects are created from classes. A Quick Introduction to Object-Orientation W.Buchanan (6)

7 using System; namespace ConsoleApplication2 Class definitions public class Cup public string Shape; public string Colour; public string Size; public int Transparency; public string Handle; Available variables (properties) Method public void DisplayCup() System.Console.WriteLine("Cup is 0, 1", Colour, Handle); class Class1 static void Main(string[] args) Cup cup = new Cup(); cup.colour = "Red"; cup.handle = "Small"; cup.displaycup(); System.Console.ReadLine(); Create new object Set properties Apply method Example C# Program using Object-Orientation W.Buchanan (7)

8 using System; namespace ConsoleApplication2 public class Circuit public double Parallel(double r1, double r2) return((r1*r2)/(r1+r2)); public double Series(double r1, double r2) return(r1+r2); Class definitions class Class1 static void Main(string[] args) double v1=100,v2=100; double res; Circuit cir = new Circuit(); res=cir.parallel(v1,v2); System.Console.WriteLine("Parallel resistance is 0 ohms",res); res=cir.series(100,100); System.Console.WriteLine("Series resistance is 0 ohms",res); System.Console.ReadLine(); Another example W.Buchanan (8)

9 using System; namespace ConsoleApplication2 public class Complex public double real; public double imag; public double mag() return (Math.Sqrt(real*real+imag*imag)); public double angle() return (Math.Atan(imag/real)*180/Math.PI); class Class1 static void Main(string[] args) string str; double mag,angle; Complex r = new Complex(); System.Console.Write("Enter real value >>"); str=system.console.readline(); r.real = Convert.ToInt32(str); System.Console.Write("Enter imag value >>"); str=system.console.readline(); r.imag = Convert.ToInt32(str); mag=r.mag(); angle=r.angle(); System.Console.WriteLine("Mag is 0 and angle is 1",mag,angle); System.Console.ReadLine(); z x jy z z x 2 tan y 1 2 y x Another example W.Buchanan (9)

10 Object Properties W.Buchanan (10)

11 Make. This could be Ford, Vauxhall, Nissan or Toyota. Type. This could be Vectra, Astra, or Mondeo. Colour. This could be colours such as Red, Green or Blue. Country of Manufacture. This could be countries such as UK, Germany or France. Car properties W.Buchanan (11)

12 using System; namespace sample01 public class Car private string colour; private string type; private string make; private string country; private double cost; public string Colour get return colour; set colour=value; public string Type get return type; set type=value; public string Country get return country; set country=value; public string Make get return make; set make=value; public double Cost get return cost; set cost=value; Relationship Tree class Class1 static void Main(string[] args) Car car1 = new Car(); car1.colour="red"; car1.make="ford"; car1.type="mondeo"; car1.colour="uk"; car1.cost=15000; Console.WriteLine( "Car is a " + car1.make + " " + car1.type); Console.ReadLine(); W.Buchanan (12)

13 public double Cost get return cost; Read-only Read/write public double Cost set val=value; public double Cost set val=value; get return cost; Write-only Read-only, write-only and read/write properties W.Buchanan (13)

14 public class Car private string colour; private string type; private string make; private string country; private double cost; public Car() country= UK ; public string Country get return country; W.Buchanan (14)

15 Object-Orientation W.Buchanan (15)

16 Let s Look At Real Objects W.Buchanan (16)

17 Plants Animals Minerals Backbone Vertebrates Invertebrates Skin with fur/hair. Red blooded. Warm blooded. Mammals Birds Classification W.Buchanan (17)

18 Collection Vertebrates Mammals Increasing generalisation Cats Dogs Horses Lion Tiger Domestic Relationship Tree Shared behaviours and characteristics Increasing specialisation W.Buchanan (18)

19 containers System Increasing generalisation Windows IO Drawing Component Model Design Forms Label Combo Box Button Form Class Increasing specialisation Relationship Tree W.Buchanan (19)

20 using System.Collections; using System.Windows.Forms; Derived using System.Data; namespace WindowsApplication3 class public class Form1 : System.Windows.Forms.Form containers private System.Windows.Forms.Button button1; Component Model private System.Windows.Forms.TextBox textbox1; public Form1() System InitializeComponent(); private void InitializeComponent() this.button1 = new System.Windows.Forms.Button(); this.textbox1 = new System.Windows.Forms.TextBox(); this.button1.location = new System.Drawing.Point(152, 192); this means Windows this object (which is Form1) this.button1.name = "button1"; this.button1.tabindex = 0; this.button1.text = "button1"; this.textbox1.location = new System.Drawing.Point(80, 64); this.textbox1.name = "textbox1"; this.textbox1.text = "textbox1"; this.controls.add(this.textbox1); Design Forms this.controls.add(this.button1); this.name = "Form1"; this.text = "Form1"; this.load += new System.EventHandler(this.Form1_Load); this.resumelayout(false); static void Main() Label Relationship Tree Combo Box Application.Run(new Form1()); private void Form1_Load(object sender, System.EventArgs e) Base class W.Buchanan (20)

21 Constructors W.Buchanan (21)

22 A constructor is a method that is called whenever the object is first created. A destructor is a method that is called whenever the object is destroyed. Constructors and destructors W.Buchanan (22)

23 class Profile string code, name, telephone; // Constructor public Profile(string c) code=c; public string Name set name=value; get return name; public string Telephone set telephone=value; get return telephone; public void Display() Console.WriteLine("Code: " + code + " Name: " + name + " Telephone: " + telephone); Console.ReadLine(); W.Buchanan (23)

24 class Profile string code, name, telephone; // Constructor public Profile(string c) code=c; public string Name set name=value; get return name; public string Telephone set telephone=value; pf1.telephone="123456"; pf1.display(); get return telephone; public void Display() class Class1 static void Main(string[] args) Profile pf1=new Profile("00000"); pf1.name="fred Smith"; Console.WriteLine("Code: " + code + " Name: " + name + " Telephone: " + telephone); Console.ReadLine(); W.Buchanan (24)

25 using System; namespace sample01 public class Car private string colour; private string type; private string make; private string country; private double cost; public Car() public Car(string m) make=m; public Car(string m, string t) make=m; type=t; W.Buchanan (25)

26 using System; namespace sample01 public class Car private string colour; private string type; private string make; private string country; private double cost; public Car() public Car(string m) make=m; public Car(string m, string t) make=m; type=t; class Class1 static void Main(string[] args) Car car1 = new Car(); car1.colour="blue"; car1.make="ford"; car1.type="mondeo"; car1.colour="uk"; car1.cost=15000; Car car2 = new Car("Ford","Mondeo"); car2.colour="red"; car2.colour="uk"; car2.cost=12000; W.Buchanan (26)

27 W.Buchanan (27)

28 Static and Instance Members W.Buchanan (28)

29 A class can either have static members of instance members. Instance members relate to the object created, while static members can be used by referring to the name of the method within the class. For example the following are calls to static members: Convert.ToInteger("str"); Console.WriteLine("Hello"); Whereas in the following, there are two instance methods (Read() and Write()), these operate on the created data type: System.IO.StreamReader nn = new StreamReader(); nn.read(); nn.write(); Instance members thus operate on an instance of a class. Static and instance members W.Buchanan (29)

30 using System;.. class Profile static int numberprofile=0; string code, name, telephone; // Constructor public Profile(string c) numberprofile++; code=c; class Class1 static void Main(string[] args) Profile pf1=new Profile("00000"); pf1.name="fred Smith"; pf1.telephone="123456"; Profile pf2=new Profile("00001"); pf2.name="fred Cannon"; pf2.telephone="223456"; Profile pf3=new Profile("00002"); pf3.name="fred McDonald"; pf3.telephone="323456"; Profile.HowMany(); public static void HowMany() Console.WriteLine("There are " + numberprofile + " profiles "); Console.ReadLine(); Using a static member to count the number of instances W.Buchanan (30)

31 Tutorial Session 8: Q8.1-Q8.7 Presentations Notes SourceCode Tutorials W.Buchanan (31)

32 Inheritance W.Buchanan (32)

33 Inheritance Derives characteristics and behaviours from those above us. Inheritance W.Buchanan (33)

34 using System; namespace ConsoleApplication1 class People private string name; public string Name containersget return name; set name=value; public void ToLowerCase() name=name.tolower(); Inheritance System class Profile : People // Inherit from People public void Display() Windows Console.WriteLine("Name: "+Name); class Test Component static void Main() Forms Model Profile p1 = new Profile(); p1.name="fred"; Design p1.tolowercase(); p1.display(); System.Console.ReadLine(); Combo Label Box Inherent from People Method derived from People People Name: fred Profile W.Buchanan (34)

35 using System; namespace ConsoleApplication1 class People private string name; public string Name containersget return name; set name=value; public void ToLowerCase() name=name.tolower(); Design Inheritance Label System class Profile : People // Inherit from People public void Display() Windows Console.WriteLine("Name: "+Name); class Test Component static void Main() Forms Model Profile p1 = new Profile(); Profile p2 = new Profile(); p1.name="fred"; p2.name="bert"; p1.tolowercase(); p1.display(); p2.display(); Combo Box System.Console.ReadLine(); Inherent from People People Name: fred Name: Bert Profile W.Buchanan (35)

36 using System; namespace ConsoleApplication1 sealed class People private string name; public string Name containersget return name; set name=value; public void ToLowerCase() name=name.tolower(); Sealed Classes System class Profile : People // Inherit from People public void Display() Windows Console.WriteLine("Name: "+Name); class Test Component static void Main() Forms Model Profile p1 = new Profile(); p1.name="fred"; Design p1.tolowercase(); p1.display(); System.Console.ReadLine(); Combo Label Box Inherent from People People Profile 'ConsoleApplication1.Profile' : cannot inherit from sealed class 'ConsoleApplication1.People' W.Buchanan (36)

37 Overriding Classes W.Buchanan (37)

38 using System; namespace ConsoleApplication1 class People private string name; class Profile : People // Inherit from People public void Display() Console.WriteLine("Name: "+Name); Name: Fred public override void ToLowerCase() Console.WriteLine("Method has been overwritten"); Overriding classes public string Name get return name; set name=value; public virtual void ToLowerCase() name=name.tolower(); class Test static void Main() Profile p1 = new Profile(); p1.name="fred"; p1.tolowercase(); p1.display(); System.Console.ReadLine(); Method has been overwritten W.Buchanan (38)

39 Object Equals(). Determines if two objects are the same. Finalize(). Cleans up the object (the destructor). GetHashCode(). Allows an object to define its hash code. GetType(). Determine the type of an object. MemberwiseClone(). Create a copy of the object. ReferenceEquals(). Determines whether two objects are of the same instance. ToString(). Convert an object to a string. Methods for the default object W.Buchanan (39)

40 using System; namespace ConsoleApplication1 class People private string name; public string Name get return name; set name=value; public virtual void ToLowerCase() name=name.tolower(); class Profile : People // Inherit from People public void Display() Console.WriteLine("Name: "+Name); public override string ToString() return("cannot implement this method"); class Test static void Main() Profile p1 = new Profile(); p1.name="fred"; string str=p1.tostring(); Console.WriteLine(str); System.Console.ReadLine(); W.Buchanan (40)

41 Abstract Classes W.Buchanan (41)

42 Here is the new object, but you can t use it unless you implement your own OpenTheBox() method! Okay. It s worth it. I ll do that. Abstract Classes W.Buchanan (42)

43 An example W.Buchanan (43)

44 using System; namespace ConsoleApplication1 abstract class People private string name; public string Name get return name; set name=value; public void ToLowerCase() name=name.tolower(); abstract public void DisplayLower(); class Profile : People // Inherit from People public void Display() Console.WriteLine("Name: "+Name); class Test static void Main() Profile p1 = new Profile(); p1.name="fred"; p1.tolowercase(); p1.display(); p1.displaylower(); System.Console.ReadLine(); 'ConsoleApplication1.Profile' does not implement inherited abstract member 'ConsoleApplication1.People.DisplayLower()' Abstract Classes W.Buchanan (44)

45 using System; namespace ConsoleApplication1 abstract class People private string name; class Test static void Main() Profile p1 = new Profile(); public string Name get return name; set name=value; public void ToLowerCase() name=name.tolower(); abstract public void DisplayLower(); class Profile : People // Inherit from People public void Display() Console.WriteLine("Name: "+Name); public override void DisplayLower() Console.WriteLine("Name: "+Name.ToUpper()); Abstract Classes p1.name="fred"; p1.tolowercase(); p1.display(); p1.displaylower(); System.Console.ReadLine(); Name: fred Name: FRED W.Buchanan (45)

46 Interfaces W.Buchanan (46)

47 Pweh! You re rather strict. Here is the new object, but you must implement it in every way that I have defined! Interfaces W.Buchanan (47)

48 R T r 1 r 2 R 1 R 2 r 1 Circuit r 2 R T R R 1 1 R 2 R 2 Circuit Object W.Buchanan (48)

49 r 1 r 2 R T R 1 R 2 r 1 r 2 interface NewCircuit double r1 set; get; double r2 set; get; double calcparallel(); double calcseries(); R T R R 1 1 R 2 R 2 Interface Definition W.Buchanan (49)

50 r 1 r 2 public class Circuit: NewCircuit private double res1, res2; public double r1 r 1 set res1=value; get return res1; public double r2 r 2 set res2=value; get return res2; public double calcparallel() return((r1*r2)/(r1+r2)); public double calcseries() return(r1+r2); Derived Class Definition R T R T R 1 R 2 R R 1 1 R 2 R interface NewCircuit double r1 set; get; double r2 set; get; double calcparallel(); double calcseries(); 2 W.Buchanan (50)

51 r 1 r 2 public class Circuit: NewCircuit private double res1, res2; public double r1 set res1=value; get return res1; public double r2 set res2=value; get return res2; public double calcparallel() return((r1*r2)/(r1+r2)); public double calcseries() return(r1+r2); Derived Class Definition r 1 r 2 R T public class Class1 R T static void Main() R 1 R 2 R R 1 1 R 2 R Circuit cir = new Circuit(); cir.r1=1000; cir.r2=1000; double res = cir.calcparallel(); System.Console.WriteLine( "Parallel Resistance is " + res); System.Console.ReadLine(); 2 W.Buchanan (51)

52 Standard Interfaces W.Buchanan (52)

53 ICollection. Defines size, enumerators and synchronization methods for all collections. The public properties are: Count, IsSynchronized and SyncRoot, and a method of CopyTo(). IComparer. Compares two objects. The associated method is Compare(). IEnumerator. Supports iteration over a collection. The properties are Current, and the methods are MoveNext() and Reset(). IList. Represents a collection of objects that are accessed by an index. The properties are IsFixedSize, IsReadOnly, Item, and the methods are: Add(), Clear(), Contains(), IndexOf(), Insert(), Remove() and RemoveAt(). W.Buchanan (53)

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55 The ICollection defines: The classes which implement ICollection include: Array. ArrayList. Hastable. Thus an array will have the following properties: Count. IsSynchronized. SyncRoot W.Buchanan (55)

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57 Tutorial Session 8: Q8.7-Q8.10 Presentations Notes SourceCode Tutorials W.Buchanan (57)