1 / 39

Implementing Association Relationships in VB.NET

Learn how to identify and implement association relationships in object-oriented application development using VB.NET. This chapter covers concepts such as one-to-one and one-to-many relationships, adding functionality to classes, and creating and using association classes.

rollinss
Download Presentation

Implementing Association Relationships in VB.NET

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 9 Implementing Association Relationships Object-Oriented Application Development Using VB .NET

  2. Objectives In this chapter, you will: • Identify association relationships on Bradshaw Marina’s class diagram • Associate VB .NET classes in a one-to-one relationship • Add functionality to the Boat class Object-Oriented Application Development Using VB .NET

  3. Objectives In this chapter, you will: • Associate Dock and Slips in a one-to-many relationship • Add the Boat and Customer classes to the Slip example • Create and use an association class—Lease Object-Oriented Application Development Using VB .NET

  4. Identifying Association Relationships on Bradshaw Marina’s Class Diagram • Association relationships • Show how instances of classes are associated, or connected, to each other • مشاهدة كيفية ارتباط النسخ وعلاقتها ببعض • Indicate that the system requires information about these associations • Can be used to navigate from instance to instance following the association • ممكن ننتقل من كلاس لكلاس عن طريق هذا الاسوسييشن Object-Oriented Application Development Using VB .NET

  5. Identifying Association Relationships on Bradshaw Marina’s Class Diagram • In a class diagram • An association relationship • Appears as a line connecting classes • تظهر كخط يربط الكلاسين • Multiplicity of the association • Indicated by numbers written at both ends of the line • الارقام الموجودة بقرب الكلاس • ممكن تسمى كاردنيلاتي كما في الاي ار ولكن الافضل تسمى مولتيسبلتي Object-Oriented Application Development Using VB .NET

  6. Identifying Association Relationships on Bradshaw Marina’s Class Diagram • Association relationships in the Bradshaw class diagram: • A customer owns a boat كل زبون يملك قارب • A boat is owned by a customer كل قارب يمتلك من زبون واحد • A boat is assigned to a slip كل قارب يسند الى سليب معين ( المكان الذي تتوقف عنده القوارب) • A slip contains a boat السليب يحتوي قارب (ون تو ون) • A dock contains many slips الدوك يحتوي على عدد من السليب (ون تو ماني) • A slip is attached to a dock • A slip is leased to a customer (Lease is an association class) هي عباره عن علاقة وكلاس في نفس الوقت • اذا العلاقة فيها اتربيوت نحطها على شكل كلاس • لماذا لا نضع الاتربيوت في احد الكلاسين المشتركه في العلاقه ، لان الاتربيوت خاصية مشتركه في كلا الكلاسين ، فيختلف من زبون الى زبون ومن سليب لاخر • A customer leases a slip (Lease is an association class) • انواع العلاقات* Object-Oriented Application Development Using VB .NET

  7. Identifying Association Relationships on Bradshaw Marina’s Class Diagram Object-Oriented Application Development Using VB .NET

  8. Identifying Association Relationships on Bradshaw Marina’s Class Diagram • Lease class • An example of an association class • Exists because of the relationship between a slip and a customer • موجودة بسبب العلاقة بين السليب والزبون • In the class diagram • Shown as a class connected by a dashed line to an association between Slip and Customer • تكتب على شكل خط مقطع الى العلاقة بين الزبون والسليب Object-Oriented Application Development Using VB .NET

  9. Associating VB .NET Classes in a One-to-One Relationship • Association relationship between Customer and Boat • أي علاقة تقرأ في الاتجاهين • Has two “directions” لها اتجاهين • A customer owns a boat (من الزبون الى القارب • A boat is owned by a customer من القارب للزبون • Each direction of the relationship • Must be defined separately by the system developer • كل اتجاه لازم يعرف منفصل من مطور النظام • Must be handled separately with VB .NET • لابد ان يعامل بشكل منفصل في الفي بي Object-Oriented Application Development Using VB .NET

  10. Associating VB .NET Classes in a One-to-One Relationship • To implement an association relationship in VB .NET • Use a reference variable as an attribute of a class • نستخدم قيمة من نوع ريفرنس (إذا شفنا كلمة ريفرنس فمعناها اوبجكت والعكس صحيح ) • A reference variable points to an actual instance Object-Oriented Application Development Using VB .NET

  11. Associating VB .NET Classes in a One-to-One Relationship Object-Oriented Application Development Using VB .NET

  12. Associating VB .NET Classes in a One-to-One Relationship • A Customer reference variable الرفرنس • Points to a Customer instance تؤشر على نسخة من الزبون • If added as an attribute in the Boat class, each Boat instance can • لما تكون العلاقة من نوع ون تو ون نضيف داخل البوت رفرنس فاربيل(اوبجكت) من نوع كوستمر • Point to a Customer instance توشر على نسخة من الزبون • Invoke the customer’s methods تتعامل مع ميثود الكوستمر Object-Oriented Application Development Using VB .NET

  13. Associating VB .NET Classes in a One-to-One Relationship • A Boat reference variable • Points to a Boat instance • If added as an attribute in the Customer class, each Customer instance can • Point to a Boat instance • Invoke the boat’s methods Object-Oriented Application Development Using VB .NET

  14. Modifying the Customer Class • Modifying the Customer class implements one direction of the association relationship • From Customer to Boat • theBoat attribute • الخلاصة في البوت نضيف اوبجكت من نوع كوستمر وفي الكوستمر نضيف اوبجكت من نوع بوت • A Boat reference variable • Added to the Customer class • Used to implement a one-to-one association relationship with the Boat class Object-Oriented Application Development Using VB .NET

  15. Modifying the Customer Class • Accessor methods • لمى نضيف الرفرنس اتربيوت نضيف له الست والقيت • SetBoat • Accepts a Boat reference as a parameter • Assigns the reference to the attribute • GetBoat • Returns the Boat reference Object-Oriented Application Development Using VB .NET

  16. Modifying the Customer Class • Constructor • Sets the Boat reference variable to Nothing using the SetBoat method • في الكونستراكتر تبع الزبون ، نضع في الاتربيوت بوت ولاشيءNOTHING • Once Customer instance is created • عندما ننشئ الزبون • Boat reference variable can be set to an actual Boat reference • عن طريق السيت نسند له قيمته Object-Oriented Application Development Using VB .NET

  17. Modifying the Boat Classالتعديل في كلاس القارب • Modifying the Boat class implements the other direction of the association relationship • A boat is owned by a customer البوت يملك بواسطة زبون ون تو ون • theCustomer attribute • A Customer reference variable نضيف اتربيوت من نوع زبون في الكلاس قارب • Added to the Boat class • Used to implement a one-to-one association relationship with the Customer class لانشاء العلاقة واحد الى واحد Object-Oriented Application Development Using VB .NET

  18. Modifying the Boat Class • Accessor methods • نضع السيت والقيت للزبون المضاف كاتربيوت في كلاس القارب • GetCustomer • Returns the Customer reference • SetCustomer • Accepts a Customer reference as a parameter • Assigns the reference to the attribute Object-Oriented Application Development Using VB .NET

  19. Adding Functionality to the Boat Class • Functionality of classes that have association relationships can be increased • AssignBoatToCustomer custom method • Added in Boat تضاف في القارب • Establishes the association between Boat and Customer in both directions in one step تنشئ العلاقة بين القارب والزبون في الاتجاهين المختلفين في خطوه وحده Object-Oriented Application Development Using VB .NET

  20. Adding Functionality to the Boat Class • Mandatory association between Boat and Customer • Possible because • Bradshaw Marina does not want to keep information about a boat if its owner is not a customer • Done by • Adding a Customer reference parameter to the Boat constructor Object-Oriented Application Development Using VB .NET

  21. Adding Functionality to the Boat Class • Modified Boat TellAboutSelf method • تعديل ميثود تيل اباوت سيلف في البوت كلاس • Returns information about • Boat • Customer • بجعلها ترجع معلومات البوت والكوستمر • Possible because • A boat must be associated with a customer • ممكنه لان القارب يجب ان يربط بزبون Object-Oriented Application Development Using VB .NET

  22. Associating Docks and Slips: A One-to-Many Association Relationship • Association relationship between Slip and Dock • Two directions of the relationship • Association relationship between Slip and Dock • One-to-one • A slip is attached to a dock • Association relationship between Dock and Slip • علاقة بين الدوك والسليب • One-to-many واحد الى كثير • A dock contains many slips Object-Oriented Application Development Using VB .NET

  23. Associating Docks and Slips: A One-to-Many Association Relationship • To implement • A one-to-one association relationship between Slip and Dock • تكون العلاقة واحد الى واحد اذا كان الاتجاه من السليب للدوك • Use the technique used to implement the Customer and Boat associations • A one-to-many association relationship between Dock and Slip • تكون العلاقة واحد الى مجموعة من الدوك للسليب • Requires that a dock instance have reference variables for more than one slip • Use an ArrayList in the Dock class to hold many Slip reference variables • نضع متغير من نوع اراي ليست يحمل العديد من اوبجتات السليب Object-Oriented Application Development Using VB .NET

  24. Associating Docks and Slips: A One-to-Many Association Relationship • ArrayList class • Can be used to instantiate a container that can hold many reference variables • فيه ميثود للاضافة للاراي ليست اسمها (اد) • Has methods which can be used to • Add Slip references تضيف اوبجكت من نوع سليب • Retrieve Slip references ونقدر نسترجع السليبز اوبجكتز Object-Oriented Application Development Using VB .NET

  25. Introducing the Dock Class • Dock class • Four previous attributes • An ID number • A location • Two Boolean variables indicating • Whether the dock has electricity • Whether the dock has water • Fifth attribute اتربيوت خامس • slips • An ArrayList • Implements the one-to-many association relationship • نسوي الامبلمنتيشن للعلاقة واحد الى مجموعة Object-Oriented Application Development Using VB .NET

  26. Introducing the Dock Class • Dock class constructor • Sets values for the four attributes وضعنا القيم في الاتربيوت الاربعة • Instantiates the new ArrayList انشاء المتغير من نوع اراي ليست • Assigns the new ArrayList to the slips attribute • GetSlips • A getter method • Returns the slips reference variable ترجع الاراي ليست اوبجكت Object-Oriented Application Development Using VB .NET

  27. Introducing the Dock Class • AddSlip custom method دالة اد سليب • Used to add a slip to the dock تستعمل لاضافة سليب للدوك • Invoked by the Slip AddSlipToDock method تستدعى من السليب عن طريق الدالة اضافة سليب الى الدوك • Contains the slips.Add(aSlip) statement • Used to add a Slip reference to the ArrayList referenced by the variable slips Object-Oriented Application Development Using VB .NET

  28. Associating the Slip Class with Dock • Modifications to the Slip class to implement the mandatory one-to-one association relationship • theDock attribute • A Dock reference variable • Accessor methods for the Dock reference attribute Object-Oriented Application Development Using VB .NET

  29. Associating the Slip Class with Dock • Modifications to the Slip class (Continued) • Modified constructor • Expects a Dock reference parameter • Result: When a slip is instantiated, it must be associated with a dock • Invokes the slip’s AddSlipToDock method • AddSlipToDock method establishes the association in both directions by • Invoking the dock’s AddSlip method using the Me keyword Object-Oriented Application Development Using VB .NET

  30. Associating the Slip Class with Dock • Modifications to the Slip class (Continued) • A TellAboutSelf method • تيل اباوت سيلف الموجوده في السليب • Returns information about • The slip • The slip’s dock • ترجع معلومات عن السليب والدوك الذي يحتويه • لا نستطيع نرجع معلومات الدوك بدون ما نضع اتربيوت من نوع دوك يحتوي على معلومات الدوك الذي ينتمي له هذا السليب Object-Oriented Application Development Using VB .NET

  31. Adding the Boat and Customer Classes to the Slip Example • Association relationship between Slip and Boat • Modifications to the Slip class • A Boat reference attribute نضيف اتربيوت من نوع بوت • Accessor methods ونضيف القيت والسيت بوت • GetBoat • SetBoat • داخل السليب نضع اتربيوت من نوع بوت واتربيوت اخر من نوع دوك • وفي البوت نضيف اتربيوت من نوع سليب واتربيوت اخر من نوع كوستمر • وفي الدوك اراي لست فيها السليبز • وفي الكوستمر نضيف فيه اتربيوت من نوع بوت • Modifications to the Boat class التعديلات في كلاس القراب • A Slip reference attribute اضافة اوبجكت من نوع سليب • Accessor methods اضافة ميثود الوصول • AssignBoatToSlip method نضيف ميثود ربط البوت بالسليب • لايمكن وضع علاقه ون تو ون اجباري في الجهتين ، لابد ان يكون احدهما اختياري 0،1 او كلاهما Object-Oriented Application Development Using VB .NET

  32. Adding the Boat and Customer Classes to the Slip Example • To include the Customer class in this example • Boat class does not need to be modified • It is already designed to associate with a customer • Given a Customer reference • Can navigate to find • The customer’s boat • The boat’s slip • The slip’s dock Object-Oriented Application Development Using VB .NET

  33. Adding the Boat and Customer Classes to the Slip Example • Given a Dock reference • Can navigate to • Each slip • The slip’s boat • The customer who owns the boat Object-Oriented Application Development Using VB .NET

  34. Creating and Using an Association Class – Lease • Lease class • An association class كلاس وعلاقة في نفس الوقت • A Lease is like an association between a customer and a slip, but with attributes for كعلاقة بين الزبون والسليب لكن مع اتربيوت لـ • Start date تاريخ البدايه • End date تاريخ النهاية • Amount of lease, and so on • Subclasses • AnnualLease • DailyLease • في الكلاس ليز نضيف اوبجكتين واحد من نوع زبون والاخر من نوع سليب • في كلاس الزبون وكلاس السليب نضيف اتربيوت واحد فقط عباره عن اوبجكت من نوع ليز ، لم نضع اتربيوت منهما لان العلاقة بينهما غير مباشرة Object-Oriented Application Development Using VB .NET

  35. Creating and Using an Association Class – Lease • Modifications to the Lease superclass • A Slip reference attribute • A Customer reference attribute • Accessor methods • AnnualLease class • A subclass of Lease • Inherits the association between ترث العلاقة بين الليز والسليب والليز والزبون • Lease and Slip • Lease and Customer Object-Oriented Application Development Using VB .NET

  36. Creating and Using an Association Class – Lease • No modifications needed for the Boat class لا تعديل على كلاس البوت • Reason: Boat is not directly associated with Lease • لان البوت ما عنده علاقه مباشرة بالليز • Modifications to the Customer class • A Lease reference attribute نضيف اوبجكت من نوع ليز • Accessor methods ميثود الوصول Object-Oriented Application Development Using VB .NET

  37. Creating and Using an Association Class – Lease • Modifications to the Slip class التعديل على كلاس اللسليب • A Lease reference attribute اوبجكت من نوع ليز • Accessor methods ميثود الوصول • LeaseAnnualSlip method ميثود ايجار سليب سنوي • Creates an AnnualLease instance تنشئ نسخة من الايجار السنوي Object-Oriented Application Development Using VB .NET

  38. Summary • Association relationships are shown on the class diagram as lines connecting classes • Association relationships are implemented in two directions that must be considered separately • Association relationships can be optional or mandatory • One-to-one association relationships are implemented by including a reference variable as an attribute in one class that points to an instance of another class Object-Oriented Application Development Using VB .NET

  39. Summary • One-to-many association relationships are implemented using an ArrayList that contains a collection of reference variables • Association relationships can be directly navigated by writing one statement with multiple method calls that are executed from left to right • An association class exists because of a relationship between two classes, such as Lease between Slip and Customer Object-Oriented Application Development Using VB .NET

More Related