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

Transcription

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

2 Course Outline Introduction to.net Day 1: Morning Introduction to Object-Orientation, Introduction to.net, Overview of.net Framework,.NET Components. C#. Introduction to Visual Studio Environment. Day 1: Afternoon Variables and Types, Naming Variables, Using Built-In Data Types, Visual Studio Environment: Design Surface - dynamic help; Toolbox; Code Page; Properties Window; Solution Explorer. Day 2: Morning Converting Data Types, Control structures: if, for, while, foreach, switch. Day 2: Afternoon File handling looking up details from help, Methods, Parameter passing, Variables and scope. Day 3: Morning REVIEW OF BASICS FROM DAY 2, Converting Data Types, Control structures: if, for, while, foreach, switch. Day 3: Afternoon Brief description of Arrays, Type Casts, Overview of System.Collections, ArrayLists and HashTables, Sorting, Enumerators Course Outline (Day 1 to 3) W.Buchanan (2)

3 Course Outline Introduction to.net Day 4: Morning Using Reference-Type Variables, Using Common Reference Types, The Object Hierarchy, Namespaces in the.net Framework, Debugging techniques, breakpoints, line stepping, call stack, locals window. Day 4: Afternoon - Classes and Objects, Using Encapsulation, C# and Object Orientation, Defining Object-Oriented Systems, Deriving es, Implementing es, Private,, internal and protected, Using Interfaces, Abstract es, Using Constructors Initializing Data, Objects and Memory, Resource Management, Object Browser, Class View. Day 5: Morning - Methods and overloaded methods, Exceptions, Intellisense and overloaded methods, Enumerations and enumeration conversion. Day 5: Afternoon: Using Modules and Assemblies, XML (read only), Serialising es. Course Outline (Day 4 and 5) W.Buchanan (3)

4 Module 8 Introduction to.net Classes and objects. Using encapsulation. Defining Object-Oriented Systems. Inheritance. Sealed es. Overriding es. Introduction W.Buchanan (4)

5 An Introduction to Object- Orientation Bill Buchanan Introduction W.Buchanan (5)

6 Some Cups W.Buchanan (6)

7 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 Introduction to.net In object-orientation:a collection of parameters defines a. Class for the cup is thus: Shape, Colour, Size, Transparency, HandleType. In object-orientation: Objects are created from es. A Quick Introduction to Object-Orientation W.Buchanan (7)

8 using System; namespace ConsoleApplication2 Class definitions Cup Shape; Colour; Size; int Transparency; Handle; Available variables (properties) Method DisplayCup() System.Console.WriteLine("Cup is 0, 1", Colour, Handle); Introduction to.net Class1 static Main([] 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 (8)

9 using System; namespace ConsoleApplication2 Circuit double Parallel(double r1, double r2) return((r1*r2)/(r1+r2)); double Series(double r1, double r2) return(r1+r2); Class definitions Introduction to.net Class1 static Main([] args) double v1100,v2100; double res; Circuit cir new Circuit(); rescir.parallel(v1,v2); System.Console.WriteLine("Parallel resistance is 0 ohms",res); rescir.series(100,100); System.Console.WriteLine("Series resistance is 0 ohms",res); System.Console.ReadLine(); Another example W.Buchanan (9)

10 using System; namespace ConsoleApplication2 Complex double real; double imag; double mag() return (Math.Sqrt(real*real+imag*imag)); double angle() return (Math.Atan(imag/real)*180/Math.PI); Class1 static Main([] args) str; double mag,angle; Complex r new Complex(); System.Console.Write("Enter real value >>"); strsystem.console.readline(); r.real Convert.ToInt32(str); System.Console.Write("Enter imag value >>"); strsystem.console.readline(); r.imag Convert.ToInt32(str); magr.mag(); angler.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 (10)

11 Object Properties Bill Buchanan Introduction W.Buchanan (11)

12 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 (12)

13 using using System; System; namespace sample01 namespace sample01 Car Car colour; colour; type; type; make; make; country; country; double double cost; cost; Colour Colour get get return return colour; colour; set set colourvalue; colourvalue; Type Type get get return return type; type; set set typevalue; typevalue; Country Country get get return return country; country; set set countryvalue; countryvalue; Make Make get get return return make; make; set set makevalue; makevalue; double double Cost Cost get get return return cost; cost; set set costvalue; costvalue; Relationship Tree Class1 static Main([] args) Car car1 new Car(); car1.colour"red"; car1.make"ford"; car1.type"mondeo"; car1.colour"uk"; car1.cost15000; Console.WriteLine( "Car is a " + car1.make + " " + car1.type); Console.ReadLine(); W.Buchanan (13)

14 double Cost get return cost; Read-only Introduction to.net Read/write double Cost set valvalue; double Cost set valvalue; get return cost; Write-only Read-only, write-only and read/write properties W.Buchanan (14)

15 Object-Orientation Bill Buchanan Introduction W.Buchanan (15)

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

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

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

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

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

21 Inheritance Bill Buchanan Introduction W.Buchanan (21)

22 Inheritance Derives characteristics and behaviours from those above us. Inheritance W.Buchanan (22)

23 using using System; System; namespace ConsoleApplication1 namespace ConsoleApplication1 name; name; containers Name Name get get return return name; name; set set namevalue; namevalue; System ToLowerCase() ToLowerCase() namename.tolower(); namename.tolower(); : : // // Inherit Inherit from from Display() Display() Windows Console.WriteLine("Name: Console.WriteLine("Name: "+Name); "+Name); Test Test Component static Component static Main() Main() Forms Model Forms Model p1 p1 new new (); (); p1.name"fred"; p1.name"fred"; Design p1.tolowercase(); Design p1.tolowercase(); p1.display(); p1.display(); System.Console.ReadLine(); System.Console.ReadLine(); Combo Combo Label Box Label Box Inheritance Inherent from Method derived from Name: fred W.Buchanan (23)

24 using using System; System; namespace ConsoleApplication1 namespace ConsoleApplication1 name; name; containers Name Name get get return return name; name; set set namevalue; namevalue; System ToLowerCase() ToLowerCase() namename.tolower(); namename.tolower(); : : // // Inherit Inherit from from Display() Display() Windows Console.WriteLine("Name: Console.WriteLine("Name: "+Name); "+Name); Test Test Component static Component static Main() Main() Forms Model Forms Model p1 p1 new new (); (); p2 p2 new new (); (); Design p1.name"fred"; Design p1.name"fred"; p2.name"bert"; p2.name"bert"; p1.tolowercase(); p1.tolowercase(); p1.display(); Combo p1.display(); Combo p2.display(); p2.display(); Label Box System.Console.ReadLine(); Label Box System.Console.ReadLine(); Inheritance Inherent from Name: fred Name: Bert W.Buchanan (24)

25 using using System; System; namespace ConsoleApplication1 namespace ConsoleApplication1 sealed sealed name; name; containers Name Name get get return return name; name; set set namevalue; namevalue; System ToLowerCase() ToLowerCase() namename.tolower(); namename.tolower(); : : // // Inherit Inherit from from Display() Display() Windows Console.WriteLine("Name: Console.WriteLine("Name: "+Name); "+Name); Test Test Component static Component static Main() Main() Forms Model Forms Model p1 p1 new new (); (); p1.name"fred"; p1.name"fred"; Design p1.tolowercase(); Design p1.tolowercase(); p1.display(); p1.display(); System.Console.ReadLine(); System.Console.ReadLine(); Combo Combo Label Box Label Box Sealed Classes Inherent from 'ConsoleApplication1.' : cannot inherit from sealed 'ConsoleApplication1.' W.Buchanan (25)

26 Overriding Classes Bill Buchanan Introduction W.Buchanan (26)

27 using using System; System; namespace namespace ConsoleApplication1 ConsoleApplication1 Test Test static static Main() Main() name; name; p1 p1 new new (); (); Name Name p1.name"fred"; p1.name"fred"; get get return return name; name; set set namevalue; p1.tolowercase(); namevalue; p1.tolowercase(); p1.display(); p1.display(); virtual virtual ToLowerCase() ToLowerCase() System.Console.ReadLine(); System.Console.ReadLine(); namename.tolower(); namename.tolower(); : : // // Inherit Inherit from from Display() Display() Method has been overwritten Console.WriteLine("Name: Console.WriteLine("Name: "+Name); "+Name); Name: Fred override override ToLowerCase() ToLowerCase() Console.WriteLine("Method Console.WriteLine("Method has has been been overwritten"); overwritten"); W.Buchanan (27) Overriding es

28 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. Methods for the default object W.Buchanan (28)

29 using using System; System; namespace namespace ConsoleApplication1 ConsoleApplication1 Test Test static static Main() Main() name; name; Name Name p1 p1 new new (); (); p1.name"fred"; p1.name"fred"; get get return return name; name; strp1.tostring(); strp1.tostring(); set set namevalue; Console.WriteLine(str); namevalue; Console.WriteLine(str); System.Console.ReadLine(); System.Console.ReadLine(); virtual virtual ToLowerCase() ToLowerCase() namename.tolower(); namename.tolower(); : : // // Inherit Inherit from from Display() Display() Console.WriteLine("Name: Console.WriteLine("Name: "+Name); "+Name); override override ToString() ToString() return("cannot return("cannot implement implement this this method"); method"); W.Buchanan (29)

30 Abstract Classes Bill Buchanan Introduction W.Buchanan (30)

31 Here Here is is the the new new object, object, but but you you can t can t use use it it unless unless you you implement your your own own OpenTheBox() method! Okay. Okay. It s It s worth worth it. it. I ll I ll do do that. that. Abstract Classes W.Buchanan (31)

32 An example W.Buchanan (32)

33 using using System; System; namespace namespace ConsoleApplication1 ConsoleApplication1 abstract abstract name; name; Name Name get get return return name; name; set set namevalue; namevalue; ToLowerCase() ToLowerCase() namename.tolower(); namename.tolower(); abstract abstract DisplayLower(); DisplayLower(); : : // // Inherit Inherit from from Display() Display() Console.WriteLine("Name: Console.WriteLine("Name: "+Name); "+Name); Test Test static static Main() Main() p1 p1 new new (); (); p1.name"fred"; p1.name"fred"; p1.tolowercase(); p1.tolowercase(); p1.display(); p1.display(); p1.displaylower(); p1.displaylower(); System.Console.ReadLine(); System.Console.ReadLine(); 'ConsoleApplication1.' does not implement inherited abstract member 'ConsoleApplication1..DisplayLower()' Abstract Classes W.Buchanan (33)

34 using System; namespace ConsoleApplication1 abstract name; Name get return name; set namevalue; ToLowerCase() namename.tolower(); abstract DisplayLower(); : // Inherit from Display() Console.WriteLine("Name: "+Name); override DisplayLower() Console.WriteLine("Name: "+Name.ToUpper()); Abstract Classes Test Test static static Main() Main() p1 p1 new new (); (); p1.name"fred"; p1.name"fred"; p1.tolowercase(); p1.tolowercase(); p1.display(); p1.display(); p1.displaylower(); p1.displaylower(); System.Console.ReadLine(); System.Console.ReadLine(); Name: fred Name: FRED W.Buchanan (34)

35 Interfaces Bill Buchanan Introduction W.Buchanan (35)

36 Here Here is is the the new new object, object, but but you you must must implement it it in in every every way way that that I I have have defined! Pweh! Pweh! You re You re rather rather strict. strict. Interfaces W.Buchanan (36)

37 r 1 r 2 R T R 1 + R 2 r 1 Introduction to.net Circuit r 2 R 1 R T R1 + R 2 R 2 Circuit Object W.Buchanan (37)

38 r 1 r 2 R T R 1 + R 2 r 1 Introduction to.net r 2 interface NewCircuit double r1 r1 set; set; get; get; double r2 r2 set; set; get; get; double calcparallel(); double calcseries(); R 1 R T R1 + R 2 R 2 Interface Definition W.Buchanan (38)

39 r 1 r 2 Circuit: NewCircuit double res1, res2; double r1 r 1 set res1value; get return res1; double r2 r 2 set res2value; get return res2; double calcparallel() return((r1*r2)/(r1+r2)); double calcseries() return(r1+r2); Derived Class Definition R T R 1 + R 2 R 1 R T R1 + R 2 R interface NewCircuit double r1 r1 set; set; get; get; double r2 r2 set; set; get; get; double calcparallel(); double calcseries(); 2 W.Buchanan (39)

40 r 1 r 2 Circuit: NewCircuit double res1, res2; double r1 set res1value; get return res1; double r2 set res2value; get return res2; double calcparallel() return((r1*r2)/(r1+r2)); double calcseries() return(r1+r2); Derived Class Definition r 1 r 2 R T R 1 + R 2 R Class1 1 R T static Main() R1 + R 2 R Circuit cir new Circuit(); cir.r11000; cir.r21000; double res cir.calcparallel(); System.Console.WriteLine( "Parallel Resistance is " + res); System.Console.ReadLine(); 2 W.Buchanan (40)

41 IOCollection. Defines size, enumerators and synchronization methods for all collections. The 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(). Introduction to.net 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 (41)

42 W.Buchanan (42)

43 The IOCollection defines: The es which implement IOCollection include: Array. ArrayList. Hastable. Thus an array will have the following properties: Introduction to.net Count. IsSynchronized. SyncRoot W.Buchanan (43)

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45 Constructors Bill Buchanan Introduction W.Buchanan (45)

46 A constructor is a method that is called whenever the object is first created. Introduction to.net A destructor is a method that is called whenever the object is destroyed. Constructors and destructors W.Buchanan (46)

47 code, name, telephone; // Constructor ( c) codec; Name set namevalue; get return name; Telephone set telephonevalue; get return telephone; Display() Console.WriteLine("Code: " + code + " Name: " + name + " Telephone: " + telephone); Console.ReadLine(); W.Buchanan (47)

48 code, name, telephone; // Constructor ( c) codec; Name set namevalue; get return name; Telephone set telephonevalue; pf1.telephone"123456"; pf1.display(); get return telephone; Display() Class1 static Main([] args) pf1new ("00000"); pf1.name"fred Smith"; Console.WriteLine("Code: " + code + " Name: " + name + " Telephone: " + telephone); Console.ReadLine(); W.Buchanan (48)

49 Static and Instance Members Bill Buchanan Introduction W.Buchanan (49)

50 A 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. For example the following are calls to static members: Convert.ToInteger("str"); Console.WriteLine("Hello"); Introduction to.net 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. Static and instance members W.Buchanan (50)

51 using System;.. static int number0; code, name, telephone; // Constructor ( c) number++; codec; Class1 static Main([] args) pf1new ("00000"); pf1.name"fred Smith"; pf1.telephone"123456"; pf2new ("00001"); pf2.name"fred Cannon"; pf2.telephone"223456"; pf3new ("00002"); pf3.name"fred McDonald"; pf3.telephone"323456";.howmany(); static HowMany() Console.WriteLine("There are " + number + " profiles "); Console.ReadLine(); Using a static member to count the number of instances W.Buchanan (51)