Using Caché Objects - InterSystems Documentation

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Object Persistence 1. Its primary (first) superclass must either be %Persistent or some other persistent class, and, 2. It must specify that its ClassType is persistent. For example: Class MyApp.MyClass Extends %Persistent [ClassType = persistent] { } If you omit the ClassType = persistent or if %Persistent (or a subclass) is not the first class in the superclass list, then your class will not be persistent. 12.2 The Persistence Interface The %Persistent class defines a set of methods, known as the Persistence Interface, that provides the means to work with object persistence. Among other things, the Persistence Interface provides the ability to save objects to the database, load objects from the database, delete objects, and test for existence. These are described in the following sections. 12.2.1 Saving Objects To save a persistent object to the database, invoke its %Save method: Set obj = ##class(MyApp.MyClass).%New() Set obj.MyValue = 10 Set sc = obj.%Save() The %Save method returns a %Status value that indicates whether the save operation succeeded or failed (such as if it has invalid property values or violates a uniqueness constraint). Calling %Save on an object automatically saves all modified objects that can be “reached” from the object being saved: that is, all embedded objects, collections, streams, referenced objects, and relationships involving the object are automatically saved if needed. The entire save operation is carried out as one transaction: if any object fails to save, then the entire transaction fails and rolls back (no changes are made to disk; all in-memory object values are what they were prior to calling %Save). When an object is saved for the first time, the %Save method automatically assigns it an Object ID value (the ID is generated using the $Increment function unless the class is using a user-provided Object ID based on property values using an idkey index) that is used to later 100 Using Caché Objects
find the object within the database. Once assigned, you cannot alter the Object ID value for a specific object instance (even if it is a user-provided ID). You can find the Object ID value for an object that has been saved using the %Id method: // Open person "22" Set person = ##class(Sample.Person).%OpenId(22) Write "Object ID: ",person.%Id(),! In more detail, the %Save method does the following: The Persistence Interface 1. First it constructs a temporary structure known as a “SaveSet.” The SaveSet is simply a graph containing references to every object that is reachable from the object being saved. The purpose of the SaveSet is to make sure that save operations involving complex sets of related objects are handled as efficiently as possible. The SaveSet also resolves any save order dependencies among objects. As each object is added to the SaveSet, its %OnAddToSaveSet callback method is called, if present. 2. It then visits each object in the SaveSet in order and checks if they are modified (that is, if any of their property values have been modified since the object was opened or last saved). If an object has been modified, it will then be saved. 3. Before being saved, each modified object is validated (its property values are tested; its %OnValidateObject method, if present, is called; and uniqueness constraints are tested); if the object is valid, the save proceeds. If any object is invalid, then the call to %Save fails and the current transaction is rolled back. 4. Before and after saving each object, the %OnBeforeSave and %OnAfterSave callback methods are called, if present. These callbacks are passed an Insert argument which indicates whether an object is being inserted (saved for the first time) or updated. If either of these callback methods fails (returns an error code) then the call to %Save fails and the current transaction is rolled back. If the current object is not modified, then %Save does not write it to disk; it returns success because the object did not need to be saved and, therefore, there is no way that there could have been a failure to save it. In fact, the return value of %Save indicates that the save operation either did all that it was asked or it was unable to do as it was asked (and not specifically whether or not anything was written to disk). Using Caché Objects 101
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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
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
Page 75 and 76: 9 Indices Indexes provide a mechani
Page 77 and 78: Index Collation 9.2 Index Collation
Page 79 and 80: 10 Using Objects with Caché Object
Page 81 and 82: Executing Methods 10.1.3 Executing
Page 83 and 84: Opening Objects 10.3 Opening Object
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
Page 99: Executing Queries // Create a Resul
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 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
Page 131 and 132: The Object-SQL Projection • The p
Page 133 and 134: If the list for a particular instan
Page 135 and 136: Triggers are, however, fired by the
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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• 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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