Using Caché Objects - InterSystems Documentation

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Objects and SQL The way to determine if a field is Always Computed or Triggered Computed is by the TRANSIENT and/or CALCULATED property keywords. If the property is transient or calculated, and has SQLCOMPUTED, the compute type is Always. If the property is not transient, not calculated, and has SQLCOMPUTED, the compute type is Triggered. An Example Suppose a class has a Name property of the form last,first. You might use the value stored in this property to create the calculated fields FirstName and LastName (each containing the first and last name, respectively). To do this, the code to set the value of the computed LastName field would be: Set {LastName}=##class(MyClass).GetLastName({Name}) where MyClass is the class being projected and GetLastName is a class method which has the following code in it: Quit $Piece(Name,",") This code simply returns the first element in the Name property that appears before the “,” delimiter. 13.2.3 Methods A class' instance methods are only accessible via the object representation of a class, and not via SQL. This is because an SQL query does not cause objects to be instantiated their (hence, their methods are not accessible). 13.2.4 SQL Triggers Because Caché SQL supports the use of triggers, any trigger associated with a class is included as part of the class' SQL projection. For more information on triggers, see the section Triggers in Using Caché SQL. Triggers are code segments executed when specific events occur in Caché SQL. Caché supports triggers based on the execution of INSERT, UPDATE, and DELETE commands. The specified code will be executed either immediately before or immediately after the relevant command is executed, depending on the trigger definition. Each event can have multiple triggers as long as they are assigned an execution order. Triggers are not fired by the persistence methods used by the default storage class, %CacheStorage. 122 Using Caché Objects
Triggers are, however, fired by the persistence methods used by the legacy storage class, %CacheSQLStorage as it uses SQL statements internally to implement its persistent behavior. 13.2.4.1 Trigger Keywords The Object-SQL Projection A class definition may include a list of trigger definitions. A trigger definition consists of the following information: Code Event Name Order Time The Caché ObjectScript code to be executed when the specified trigger event occurs. Triggers fully support all Caché ObjectScript functionality including embedded SQL and object syntax. The event with which this trigger is associated. Possible events include INSERT, UPDATE, DELETE. Together with the Time value, this determines when a trigger is invoked. The name of the trigger. This must be unique within the extent of the trigger. A number indicating the order in which trigger actions are to be carried out when more than one trigger is defined for a specific event. If only one trigger is associated with a specific event its order must be set to 1. If more than one trigger is associated with a specific event, each must have a unique order value. Together with the Event keyword, Time determines when a trigger is invoked. The possible values of Time are BEFORE and AFTER. 13.2.5 Relationships The SQL projection of a relationship depends on its cardinality value: The single-valued side (ONE or PARENT) is projected as a simple designative reference field. For example, the Employee table will have a field called TheCompany whose value is the ID of the related Company: Using Caché Objects 123
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Using Caché Objects Version 5.2 01
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Table of Contents 1 Introduction to
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7 Properties ......................
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13.1 Inheritance and SQL ..........
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20.8 %OnNew .......................
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List of Figures Embeddable Objects
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1 Introduction to Caché Objects Th
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1.2 Class Definitions and the Class
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Development Tools Caché Class Libr
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• The Caché EJB Binding—a vers
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2 Object-Oriented Database Developm
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Encapsulation Caché exploits inher
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3 The Caché Object Model The Cach
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Referring to an Object — OREF, OI
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Types of Classes 3.2.1 Transient Ob
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Types of Classes Embeddable Objects
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A class inherits all of the specifi
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2. It resolves inheritance—it det
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Caché Classes • Class Parameters
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Caché Classes ClientDataType Descr
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Caché Classes Internally, this wor
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Packages Class Packages Any of thes
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Packages Letting the compiler resol
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Packages • “%Library” —any
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Methods where count and state are d
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Methods 6.4 Method Language You hav
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Methods 6.6 Instance and Class Meth
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Methods Write dog.Speak() Which cou
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Properties 7.1 Property Keywords Yo
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Properties Property Behavior The pr
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Properties 7.5 Attribute Properties
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Properties You can manipulate a col
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8 Class Queries Class queries provi
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Query Basics Final Specifies that s
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Caché ObjectScript. These queries
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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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Page 85 and 86: where oref is the OREF of the speci
Page 87 and 88: For example, to populate the Home p
Page 89 and 90: change the second vaccination recor
Page 91 and 92: There are two types of array proper
Page 93 and 94: Saving Objects 10.5 Saving Objects
Page 95 and 96: mation. Again, this method deletes
Page 97 and 98: Set rset = ##class(%ResultSet).%New
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Page 102 and 103: Data Types 11.1 Available Types Cac
Page 104 and 105: Data Types • INDEXSUBSCRIPTS —
Page 106 and 107: Data Types CLIENTDATATYPE Values Va
Page 108 and 109: Data Types SQLCATEGORY Values Value
Page 110 and 111: Data Types The property is restrict
Page 112 and 113: Object Persistence 1. Its primary (
Page 114 and 115: Object Persistence Note: In a multi
Page 116 and 117: Object Persistence // Open person "
Page 118 and 119: Object Persistence For example: //
Page 120 and 121: Object Persistence If a persistent
Page 122 and 123: Object Persistence The storage clas
Page 125 and 126: 13 Objects and SQL A key aspect of
Page 127 and 128: The Object-SQL Projection 13.2 The
Page 129 and 130: The Object-SQL Projection 13.2.2.1
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Page 133: If the list for a particular instan
Page 137 and 138: 14 Relationships A relationship is
Page 139 and 140: Relationship Basics the relationshi
Page 141 and 142: An Invoice class class MyApp.Invoic
Page 143: 14.4 Persistent Behavior of Relatio
Page 146 and 147: Streams Stream data may be stored i
Page 148 and 149: Streams 15.2.2 Copying Data between
Page 150 and 151: Streams Set stream=##class(%Stream.
Page 153 and 154: 16 Class Projections Class projecti
Page 155 and 156: RemoveProjection The RemoveProjecti
Page 157 and 158: 17 Object Synchronization Object sy
Page 159 and 160: About Updates • If two changes re
Page 161 and 162: About Updates Two Synchronized Data
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Page 165 and 166: Set Status = TargetSyncSet.Import(f
Page 167 and 168: 18 Method Generators A powerful fea
Page 169 and 170: Method Generator Context 6. It copi
Page 171: Implementing Method Generators 3. A
Page 174 and 175: The Caché Data Population Utility
Page 182 and 183: 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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