Defining and Using Classes

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Contents

InterSystems: The power behind what matters

Preface :	About This Book

Chapter 1:	Basic Ideas in Class Programming
	1.1 Objects and Properties 1.2 Methods 1.2.1 Instance Methods 1.2.2 Class Methods 1.2.3 Methods and Variable Scope 1.3 Class Constants (Parameters) 1.4 Class Definitions and Types 1.5 Inheritance 1.5.1 Terminology and Basics 1.5.2 Example 1.5.3 Use of Inherited Class Members 1.5.4 Use of Subclasses 1.6 Classes as Containers of Methods 1.7 Abstract Classes
Chapter 2:	Defining and Compiling Classes
	2.1 Introduction to Terminology 2.2 Kinds of Classes 2.2.1 Object Classes 2.2.2 Data Type Classes 2.3 Kinds of Class Members 2.3.1 Kinds of Properties 2.4 Defining a Class: The Basics 2.4.1 Choosing a Superclass 2.4.2 Include Files 2.4.3 Specifying Class Keywords 2.4.4 Introduction to Defining Class Parameters 2.4.5 Introduction to Defining Properties 2.4.6 Introduction to Defining Methods 2.5 Naming Conventions 2.5.1 Rules for Class and Class Member Names 2.5.2 Class Names 2.5.3 Class Member Names 2.6 Inheritance 2.6.1 Use of Subclasses 2.6.2 Primary Superclass 2.6.3 Multiple Inheritance 2.6.4 Additional Topics 2.7 Introduction to Compiler Keywords 2.7.1 Example 2.8 Creating Class Documentation 2.8.1 Introduction to the Class Reference 2.8.2 Creating Documentation to Include in the Class Reference 2.8.3 Using HTML Markup in Class Documentation 2.9 Compiling Classes 2.9.1 Invoking the Class Compiler 2.9.2 Class Compiler Notes 2.10 Making Classes Deployed 2.10.1 About Deployed Mode
Chapter 3:	Package Options
	3.1 Overview of Packages 3.2 Package Names 3.3 Defining Packages 3.4 Package Mapping 3.4.1 Mapping a Package Across Multiple Namespaces 3.5 Package Use When Referring to Classes 3.6 Importing Packages 3.6.1 Class Import Directive 3.6.2 ObjectScript #IMPORT Directive 3.6.3 Explicit Package Import Affects Access to User Package 3.6.4 Package Import and Inheritance 3.6.5 Tips for Importing Packages
Chapter 4:	Defining and Referring to Class Parameters
	4.1 Introduction to Class Parameters 4.2 Defining Class Parameters 4.3 Parameter Types and Values 4.3.1 Class Parameter to Be Evaluated at Runtime (COSEXPRESSION) 4.3.2 Class Parameter to Be Evaluated at Compile Time (Curly Braces) 4.3.3 Class Parameter to Be Updated at Runtime (CONFIGVALUE) 4.4 Referring to Parameters of a Class
Chapter 5:	Defining and Calling Methods
	5.1 Introduction to Methods 5.2 Defining Methods 5.3 Specifying Method Arguments: Basics 5.4 Indicating How Arguments Are to Be Passed 5.5 Specifying a Variable Number of Arguments 5.6 Returning a Value 5.7 Specifying the Implementation Language 5.8 Types of Methods (CodeMode Options) 5.8.1 Code Methods 5.8.2 Expression Methods 5.8.3 Call Methods 5.8.4 Method Generators 5.9 Projecting a Method As an SQL Stored Procedure 5.10 Calling Class Methods 5.10.1 Passing Arguments to a Method 5.11 Casting a Method 5.12 Overriding an Inherited Method 5.12.1 ##super() 5.12.2 ##super and Method Arguments 5.12.3 Calls That ##super Affects 5.12.4 Number of Arguments
Chapter 6:	Working with Registered Objects
	6.1 Introduction to Object Classes 6.2 OREF Basics 6.2.1 INVALID OREF Error 6.2.2 Testing an OREF 6.2.3 OREFs, Scope, and Memory 6.2.4 Removing an OREF 6.2.5 OREFs, the SET Command, and System Functions 6.3 Creating New Objects 6.4 Viewing Object Contents 6.5 Introduction to Dot Syntax 6.5.1 Cascading Dot Syntax 6.5.2 Cascading Dot Syntax with a Null OREF 6.6 Validating Objects 6.7 Determining an Object Type 6.7.1 %Extends() 6.7.2 %IsA() 6.7.3 %ClassName() and the Most Specific Type Class (MSTC) 6.8 Cloning Objects 6.9 Referring to Properties of an Instance 6.10 Calling Methods of an Instance 6.11 Obtaining the Class Name from an Instance 6.12 $this Variable (Current Instance) 6.13 i%PropertyName (Instance Variables)
Chapter 7:	Introduction to Persistent Objects
	7.1 Persistent Classes 7.2 Introduction to the Default SQL Projection 7.3 Identifiers for Saved Objects: ID and OID 7.3.1 Projection of Object IDs to SQL 7.3.2 Object IDs in SQL 7.4 Class Members Specific to Persistent Classes 7.4.1 Storage Definitions 7.4.2 Indices 7.4.3 Foreign Keys 7.4.4 Triggers 7.5 Other Class Members 7.6 Extents 7.7 Extent Management 7.8 Extent Queries
Chapter 8:	Working with Persistent Objects
	8.1 Saving Objects 8.1.1 Rollback 8.1.2 Saving Objects and Transactions 8.2 Testing the Existence of Saved Objects 8.2.1 Testing for Object Existence with ObjectScript 8.2.2 Testing for Object Existence with SQL 8.3 Opening Saved Objects 8.3.1 Multiple Calls to %OpenId() 8.3.2 Concurrency 8.4 Swizzling 8.5 Reloading an Object from Disk 8.6 Reading Stored Values 8.7 Deleting Saved Objects 8.7.1 The %DeleteId() Method 8.7.2 The %DeleteExtent() Method 8.7.3 The %KillExtent() Method 8.8 Accessing Object Identifiers 8.9 Object Concurrency Options 8.9.1 Why Specify Concurrency? 8.9.2 Concurrency Values 8.9.3 Concurrency and Swizzled Objects 8.10 Version Checking (Alternative to Concurrency Argument)
Chapter 9:	Defining Persistent Classes
	9.1 Defining a Persistent Class 9.2 Projection of Packages to Schemas 9.3 Specifying the Table Name for a Persistent Class 9.4 Storage Definitions and Storage Classes 9.4.1 Updates to a Storage Definition 9.4.2 The %CacheStorage Storage Class 9.4.3 The %CacheSQLStorage Storage Class 9.5 Schema Evolution 9.6 Resetting the Storage Definition 9.7 Controlling How IDs Are Generated 9.8 Controlling the SQL Projection of Subclasses 9.8.1 Default SQL Projection of Subclasses 9.8.2 Alternative SQL Projection of Subclasses 9.9 Redefining a Persistent Class That Has Stored Data
Chapter 10:	Defining and Using Literal Properties
	10.1 Defining Literal Properties 10.1.1 Examples 10.2 Defining an Initial Expression for a Property 10.3 Defining a Property As Required 10.4 Defining a Computed Property 10.5 Defining a Multidimensional Property 10.6 Common Data Type Classes 10.6.1 Data Type Classes Grouped by SqlCategory 10.6.2 Data Type Classes Grouped by OdbcType 10.6.3 Data Type Classes Grouped by ClientDataType 10.7 Core Property Parameters 10.8 Class-Specific Property Parameters 10.8.1 Common Parameters 10.8.2 Parameters for XML and SOAP 10.8.3 Less Common Parameters 10.9 Defining Enumerated Properties 10.10 Specifying Values for Literal Properties 10.10.1 Specifying Values for a Multidimensional Property 10.11 Using Property Methods 10.12 Controlling the SQL Projection of Literal Properties 10.12.1 Specifying the Field Names 10.12.2 Specifying the Column Numbers 10.12.3 Effect of the Data Type Class and Property Parameters 10.12.4 Controlling the SQL Projection of Computed Properties
Chapter 11:	Working with Collections
	11.1 Introduction to Collections 11.2 Defining Collection Properties 11.3 Adding Items to a List Property 11.4 Adding Items to an Array Property 11.5 Working with List Properties 11.6 Working with Array Properties 11.7 Copying Collection Data 11.8 Controlling the SQL Projection of Collection Properties 11.8.1 Default Projection of List Properties 11.8.2 Default Projection of Array Properties 11.8.3 Alternative Projections of Collections 11.9 Creating and Using Stand-Alone Collections
Chapter 12:	Working with Streams
	12.1 Introduction to Stream Classes 12.2 Declaring Stream Properties 12.3 Using the Stream Interface 12.3.1 Commonly Used Stream Methods and Properties 12.3.2 Reading and Writing Stream Data 12.3.3 Copying Data between Streams 12.3.4 Inserting Stream Data 12.3.5 Finding Literal Values in a Stream 12.3.6 Using Streams in Object Applications 12.4 Stream Classes for Use with gzip Files 12.5 Projection of Stream Properties to SQL and ODBC 12.5.1 Reading a Stream via Embedded SQL 12.5.2 Writing a Stream via Embedded SQL
Chapter 13:	Defining and Using Object-Valued Properties
	13.1 Defining Object-Valued Properties 13.1.1 Variation: CLASSNAME Parameter 13.2 Introduction to Serial Objects 13.3 Possible Combinations of Objects 13.3.1 Terms for Object-Valued Properties 13.4 Specifying the Value of an Object Property 13.5 Saving Changes 13.6 SQL Projection of Object-Valued Properties 13.6.1 Reference Properties 13.6.2 Embedded Object Properties
Chapter 14:	Defining and Using Relationships
	14.1 Overview of Relationships 14.1.1 One-to-Many Relationships 14.1.2 Parent-Child Relationships 14.1.3 Common Relationship Terminology 14.2 Defining a Relationship 14.2.1 General Syntax 14.2.2 Defining a One-to-Many Relationship 14.2.3 Defining a Parent-Child Relationship 14.3 Examples 14.3.1 Example One-to-Many Relationship 14.3.2 Example Parent-Child Relationship 14.4 Connecting Objects 14.4.1 Scenario 1: Updating the Many or Child Side 14.4.2 Scenario 2: Updating the One or Parent Side 14.4.3 Fastest Way to Connect Objects 14.5 Removing a Relationship 14.6 Deleting Objects in Relationships 14.7 Working with Relationships 14.8 SQL Projection of Relationships 14.8.1 SQL Projection of One-to-Many Relationships 14.8.2 SQL Projection of Parent-Child Relationships 14.9 Creating Many-to-Many Relationships 14.9.1 Variation with Foreign Keys
Chapter 15:	Other Options for Persistent Classes
	15.1 Defining a Read-Only Class 15.2 Adding Indices 15.3 Adding Foreign Keys 15.4 Adding Triggers 15.5 Referring to Fields from ObjectScript 15.6 Adding Row-Level Security 15.6.1 Setting Up Row-Level Security 15.6.2 Adding Row-Level Security to a Table with Existing Data 15.6.3 Performance Tips and Information 15.6.4 Security Tips and Information
Chapter 16:	Defining Method and Trigger Generators
	16.1 Introduction 16.2 Basics 16.3 How Generators Work 16.4 Values Available to Method Generators 16.5 Values Available to Trigger Generators 16.6 Defining Method Generators 16.6.1 Specifying CodeMode within a Method Generator 16.7 Generators and INT Code 16.8 Generator Methods and Subclasses 16.8.1 Method Regeneration in Subclasses 16.8.2 Invoking the Method in the Superclass 16.8.3 Removing a Generated Method
Chapter 17:	Defining and Using Class Queries
	17.1 Introduction to Class Queries 17.2 Using Class Queries 17.3 Defining Basic Class Queries 17.3.1 Example 17.3.2 About ROWSPEC 17.3.3 About CONTAINID 17.3.4 Other Parameters of the Query Class 17.4 Defining Custom Class Queries 17.4.1 Defining the querynameExecute() Method 17.4.2 Defining the querynameFetch() Method 17.4.3 The querynameClose() Method 17.4.4 Generated Methods for Custom Queries 17.5 Defining Parameters for Custom Queries 17.6 Additional Custom Query Example 17.7 When to Use Custom Queries 17.8 SQL Cursors and Class Queries
Chapter 18:	Defining and Using XData Blocks
	18.1 Basics 18.2 Using XData (Example)
Chapter 19:	Defining Class Projections
	19.1 Introduction 19.2 Adding a Projection to a Class 19.3 Creating a New Projection Class 19.3.1 The Projection Interface
Chapter 20:	Defining Callback Methods
	20.1 Callbacks and Triggers 20.2 %OnAddToSaveSet() 20.3 %OnAfterBuildIndices() 20.4 %OnAfterDelete() 20.5 %OnAfterPurgeIndices() 20.6 %OnAfterSave() 20.7 %OnBeforeBuildIndices() 20.8 %OnBeforePurgeIndices() 20.9 %OnBeforeSave() 20.10 %OnClose() 20.11 %OnConstructClone() 20.12 %OnDelete() 20.13 %OnNew() 20.14 %OnOpen() 20.15 %OnReload 20.16 %OnRollBack() 20.17 %OnValidateObject() 20.18 %OnDetermineClass() 20.18.1 Invoking %OnDetermineClass() 20.18.2 An Example of Results of Calls to %OnDetermineClass()
Chapter 21:	Using and Overriding Property Methods
	21.1 Introduction to Property Methods 21.2 Property Accessors for Literal Properties 21.3 Property Accessors for Object-Valued Properties 21.4 Overriding a Property Getter Method 21.5 Overriding a Property Setter Method 21.6 Defining an Object-Valued Property with a Custom Accessor Method
Chapter 22:	Defining Data Type Classes
	22.1 Overview of Data Type Classes 22.1.1 Property Methods 22.1.2 Data Formats 22.1.3 Parameters in Data Type Classes 22.2 Defining a Data Type Class 22.3 Defining Class Methods in Data Type Classes 22.4 Defining Instance Methods in Data Type Classes
Chapter 23:	Implementing Dynamic Dispatch
	23.1 Introduction to Dynamic Dispatch 23.2 Content of Methods Implementing Dynamic Dispatch 23.2.1 Return Values 23.3 The Dynamic Dispatch Methods 23.3.1 %DispatchMethod() 23.3.2 %DispatchClassMethod() 23.3.3 %DispatchGetProperty() 23.3.4 %DispatchSetProperty() 23.3.5 %DispatchSetMultidimProperty()
Appendix A:	Object-Specific ObjectScript Features
	A.1 Relative Dot Syntax (..) A.2 ##Class Syntax A.2.1 Invoking a Class Method A.2.2 Casting a Method A.2.3 Accessing a Class Parameter A.3 $this Syntax A.4 ##super Syntax A.4.1 Calls That ##super Affects A.4.2 ##super and Method Arguments A.5 Dynamically Accessing Objects A.5.1 $CLASSNAME A.5.2 $CLASSMETHOD A.5.3 $METHOD A.5.4 $PARAMETER A.5.5 $PROPERTY A.6 i%<PropertyName> Syntax A.7 ..#<Parameter> Syntax
Appendix B:	Using the Populate Utility
	B.1 Data Population Basics B.1.1 Populate() Details B.2 Default Behavior B.2.1 Literal Properties B.2.2 Collection Properties B.2.3 Properties That Refer to Serial Objects B.2.4 Properties That Refer to Persistent Objects B.2.5 Relationship Properties B.3 Specifying the POPSPEC Parameter B.3.1 Specifying the POPSPEC Parameter for Non-Collection Properties B.3.2 Specifying the POPSPEC Parameter for List Properties B.3.3 Specifying the POPSPEC Parameter for Array Properties B.3.4 Specifying the POPSPEC Parameter via an SQL Table B.4 Basing One Generated Property on Another B.5 How %Populate Works B.6 Custom Populate Actions and the OnPopulate() Method B.7 Alternative Approach: Creating a Utility Method B.7.1 Tips for Building Structure into the Data
Appendix C:	Using the %Dictionary Classes
	C.1 Introduction to Class Definition Classes C.2 Browsing Class Definitions C.3 Altering Class Definitions
Appendix D:	Using the Object Synchronization Feature
	D.1 Introduction to Object Synchronization D.1.1 The GUID D.1.2 How Updates Work D.1.3 The SyncSet and SyncTime Objects D.2 Modifying the Classes to Support Synchronization D.3 Performing the Synchronization D.4 Translating Between GUIDs and OIDs D.5 Manually Updating a SyncTime Table