Using Caché Objects - InterSystems Documentation

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Object-Oriented Database Development 2.5 Extensibility One of the key features of object-oriented systems is that they are extensible: it is possible to tailor their behavior for specific applications. Typically such extensibility is achieved in the following ways: • Type definition: You can define new data types that represent application-specific data. • Event handling: An application can define a set of methods that are called when certain events occur. By providing such methods, the behavior of an application can be modified without having to change its core implementation. • Subclassing: An application can adapt previously developed components for new uses by creating subclasses of existing classes. 2.6 Object Persistence Object persistence refers to the ability to store object instances within a database. Caché is unique in that such object can be fully queried using native (i.e., direct against the data) SQL queries. Caché can store objects natively; that is, objects are not first converted into a relational representation. Instead each persistent object has methods (generated automatically) that directly store and load objects into the Caché data engine. The persistence model automatically manages concurrency, transactions, and validation. In addition, Caché supports the idea of Schema Evolution: if you change your data model, it is still possible to use previously stored objects. 2.7 Object Binding An object binding is a mechanism by which a Caché object can project itself as a native object in a different environment. For example, Caché supports a Java binding by which any Caché object can be used within a Java environment as if it were a native Java class. Bindings exist for languages such as Java, C++, Perl, Python, XML, ActiveX, and the .net Managed Provider. 12 Using Caché Objects
3 The Caché Object Model The Caché object model defines the behavior and features of both persistent (database) objects as well as transient objects (those not stored). The Caché object model supports the following features: • Persistence—Objects can be stored within the Caché database or in an external database. Stored objects are simultaneously projected as relational tables and can be queried using standard SQL. The object model is rich enough to define the complete information required for complex database applications (such as indices, storage structure, integrity constraints, etc.). • Properties—Objects can contain both simple (literal) or object-valued properties. Objectvalued properties can be references to external objects or embedded objects. There are also a variety of relationship, collection, and stream properties. • Custom Data Types—Objects can use application-specific data types which are themselves defined as classes. • Methods—Objects have behavior associated with them. • Polymorphism—Applications can easily adapt to new circumstances by providing specialized implementations of operations. The runtime system automatically invokes the correct implementation based on object type. • Inheritance—Applications can reuse code by deriving new components from pre-existing classes. Using Caché Objects 13
Page 1 and 2: Using Caché Objects Version 5.2 01
Page 3 and 4: Table of Contents 1 Introduction to
Page 5 and 6: 7 Properties ......................
Page 7 and 8: 13.1 Inheritance and SQL ..........
Page 9 and 10: 20.8 %OnNew .......................
Page 11 and 12: List of Figures Embeddable Objects
Page 13 and 14: 1 Introduction to Caché Objects Th
Page 15 and 16: 1.2 Class Definitions and the Class
Page 17 and 18: Development Tools Caché Class Libr
Page 19 and 20: • The Caché EJB Binding—a vers
Page 21 and 22: 2 Object-Oriented Database Developm
Page 23: Encapsulation Caché exploits inher
Page 27 and 28: Referring to an Object — OREF, OI
Page 29 and 30: Types of Classes 3.2.1 Transient Ob
Page 31 and 32: Types of Classes Embeddable Objects
Page 33 and 34: A class inherits all of the specifi
Page 35: 2. It resolves inheritance—it det
Page 38 and 39: Caché Classes • Class Parameters
Page 40 and 41: Caché Classes ClientDataType Descr
Page 42 and 43: Caché Classes Internally, this wor
Page 44 and 45: Packages Class Packages Any of thes
Page 46 and 47: Packages Letting the compiler resol
Page 48 and 49: Packages • “%Library” —any
Page 50 and 51: Methods where count and state are d
Page 52 and 53: Methods 6.4 Method Language You hav
Page 54 and 55: Methods 6.6 Instance and Class Meth
Page 56 and 57: Methods Write dog.Speak() Which cou
Page 58 and 59: Properties 7.1 Property Keywords Yo
Page 60 and 61: Properties Property Behavior The pr
Page 62 and 63: Properties 7.5 Attribute Properties
Page 64 and 65: Properties You can manipulate a col
Page 67 and 68: 8 Class Queries Class queries provi
Page 69 and 70: Query Basics Final Specifies that s
Page 71 and 72: Caché ObjectScript. These queries
Page 73 and 74: The data in Row is the result of ex
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9 Indices Indexes provide a mechani
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Index Collation 9.2 Index Collation
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10 Using Objects with Caché Object
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Executing Methods 10.1.3 Executing
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Opening Objects 10.3 Opening Object
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where oref is the OREF of the speci
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For example, to populate the Home p
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change the second vaccination recor
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There are two types of array proper
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Saving Objects 10.5 Saving Objects
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mation. Again, this method deletes
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Set rset = ##class(%ResultSet).%New
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Executing Queries // Create a Resul
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Data Types 11.1 Available Types Cac
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Data Types • INDEXSUBSCRIPTS —
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Data Types CLIENTDATATYPE Values Va
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Data Types SQLCATEGORY Values Value
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Data Types The property is restrict
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Object Persistence 1. Its primary (
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Object Persistence Note: In a multi
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Object Persistence // Open person "
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Object Persistence For example: //
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Object Persistence If a persistent
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Object Persistence The storage clas
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13 Objects and SQL A key aspect of
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The Object-SQL Projection 13.2 The
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The Object-SQL Projection 13.2.2.1
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The Object-SQL Projection • The p
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If the list for a particular instan
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Triggers are, however, fired by the
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14 Relationships A relationship is
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Relationship Basics the relationshi
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An Invoice class class MyApp.Invoic
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14.4 Persistent Behavior of Relatio
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Streams Stream data may be stored i
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Streams 15.2.2 Copying Data between
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Streams Set stream=##class(%Stream.
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16 Class Projections Class projecti
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RemoveProjection The RemoveProjecti
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17 Object Synchronization Object sy
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About Updates • If two changes re
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About Updates Two Synchronized Data
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• classname is a quoted string th
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Set Status = TargetSyncSet.Import(f
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18 Method Generators A powerful fea
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Method Generator Context 6. It copi
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Implementing Method Generators 3. A
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The Caché Data Population Utility
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Using Callback Methods Since differ
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Using Callback Methods ReturnValue
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Using Callback Methods 20.6 %OnDele
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Using Callback Methods 20.10 %OnRol
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21 Object-Specific ObjectScript Fea
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##this Syntax >Do ##class(Package.C
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##super Syntax 21.4 ##super Syntax
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You can override a property's defau
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Dynamic Dispatch 22.2 Content of Me
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Dynamic Dispatch %DispatchMethod ca
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23 Class Definition Classes The Cac
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You can get detailed information ab
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Internet Classes addressed to , its
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Internet Classes For more informati
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Object Concurrency Setting 1 2 3 4
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Object Concurrency Note: You can us
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