Using Caché Objects - InterSystems Documentation

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Method Generators Class MyApp.MyClass Extends %RegisteredObject { Method MyMethod() [ CodeMode = objectgenerator ] { Do %code.WriteLine(" Write """ _ %class.Name _ """") Do %code.WriteLine(" Quit") Quit $$$OK } } When the class MyApp.MyClass is compiled, it ends up with a MyMethod method with the following implementation: Write "MyApp.MyClass" Quit Note: The value of CodeMode in the previous example is “objectgenerator” , since this method generator uses the preferred, object-based, method generator mechanism. Prior to version 5 of Caché, there was a different preferred mechanism, in which the value of CodeMode was “generator” . While the older mechanism is preserved for compatibility, new applications should use “objectgenerator” . 18.2 How Method Generators Work The operation of a method generator is straightforward. When you compile a class definition, the Class Compiler does the following: 1. It resolves inheritance for the class (builds a list of all inherited members). 2. It makes a list of all methods specified as method generators (by looking at the CodeMode keyword of each method). 3. It gathers the code from all method generators, copies it into one or more temporary routines, and compiles them (this makes it possible to execute the method generator code). 4. It creates a set of transient objects that represent the definition of the class being compiled. These objects are made available to the method generator code. 5. It executes the code for every method generator. If present, the compiler will arrange the order in which it invokes the method generators by looking at the value of the GenerateAfter keyword for each of the methods. This keyword gives you some control in cases where there may be compiler timing dependencies among methods. 156 Using Caché Objects
Method Generator Context 6. It copies the results of each method generator (lines of code plus any changes to other method keywords) into the compiled class structure (used to generate the actual code for the class). Note that the original method signature (arguments and return type), as well as any method keyword values, are used for the generated method. If you specify a method generator as having a return type of %Integer, then the actual method will have a return type of %Integer. 7. It generates the executable code for the class by combining the code generated by the method generators along with the code from all the non-method generator methods. 18.3 Method Generator Context The key to implementing method generators is understanding the context in which method generator code is executed. As described in the previous section, the class compiler invokes the method generator code at the point after it has resolved class inheritance but before it has generated code for the class. When it invokes method generator code, the class compiler creates the following object instances and makes them available to the method generator code: Objects Available to Method Generators Object %code %class %method %compiledclass %compiledmethod Description An instance of the %Stream.MethodGenerator class. This is a stream into which you write the code for method. An instance of the %Dictionary.ClassDefinition class. It contains the original definition of the class being compiled. An instance of the %Dictionary.MethodDefinition class. It contains the original definition of the method being compiled. An instance of the %Dictionary.CompiledClass class. It contains the compiled definition of the class being compiled. It contains information about the class after inheritance has been resolved (such as the list of all properties and methods, including those inherited from superclasses). An instance of the %Dictionary.CompiledMethod class. It contains the compiled definition of the method being generated. Using Caché Objects 157
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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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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 "
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
Page 163 and 164: • classname is a quoted string th
Page 165 and 166: Set Status = TargetSyncSet.Import(f
Page 167: 18 Method Generators A powerful fea
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
Page 184 and 185: Using Callback Methods ReturnValue
Page 186 and 187: Using Callback Methods 20.6 %OnDele
Page 188 and 189: Using Callback Methods 20.10 %OnRol
Page 191 and 192: 21 Object-Specific ObjectScript Fea
Page 193 and 194: ##this Syntax >Do ##class(Package.C
Page 195 and 196: ##super Syntax 21.4 ##super Syntax
Page 197: You can override a property's defau
Page 200 and 201: Dynamic Dispatch 22.2 Content of Me
Page 202 and 203: Dynamic Dispatch %DispatchMethod ca
Page 205 and 206: 23 Class Definition Classes The Cac
Page 207: You can get detailed information ab
Page 210 and 211: Internet Classes addressed to , its
Page 212 and 213: Internet Classes For more informati
Page 214 and 215: Object Concurrency Setting 1 2 3 4
Page 216 and 217: Object Concurrency Note: You can us
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