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1-130 SOMobjects Base Toolkit: Programmer’s Reference Manual

somDefaultInit Method

Purpose

Initializes instance variables and attributes in a newly created object. Replaces somInit as

the preferred method for default object initialization. For performance reasons, it is

recommended that somDefaultInit always be overridden by classes.

Syntax

void somDefaultInit (inout somInitCtrl ctrl );

Description

Every SOM class is expected to support a set of initializer methods. This set will always

include somDefaultInit, whether or not the class explicitly overrides somDefaultInit. All

other initializer methods for a class must be explicitly introduced by the class. See Section

5.5, “Initializing and Uninitializing Objects,” of the SOMobjects Developer Toolkit Users

Guide for complete information on introducing new initializers.

The purpose of an initializer method supported by a class is first to invoke initializer

methods of ancestor classes (those ancestors that are the class’s directinitclasses) and

then to place the instance variables and attributes introduced by the class into some

consistent state by loading them with appropriate values. The result is that, when an object

is initialized, each class that contributes to its implementation will run some initializer

method. The somDefaultInit method may or may not be among the initializers used to

initialize a given object, but it is always available for this purpose.

Thus, the somDefaultInit method may be invoked on a newly created object to initialize its

instance variables and attributes. The somDefaultInit method is more efficient than somInit

(the method it replaces), and it also prevents multiple initializer calls to ancestor classes.

The somInit method is now considered obsolete when writing new code, although somInit

is still supported.

To override somDefaultInit, the implementation section of the class’s .idl file should

include somDefaultInit with the override and init modifiers specified. (The init modifier

signifies that the method is an initializer method.) No additional coding is required for the

resulting somDefaultInit stub procedure in the implementation template file, unless the

class implementor wishes to customize object initialization in some way.

If the .idl file does not explicitly override somDefaultInit, then by default a generic method

procedure for somDefaultInit will be provided by the SOMobjects Toolkit. If invoked, this

generic method procedure first invokes somDefaultInit on the appropriate ancestor

classes, and then (for consistency with earlier versions of SOMobjects) calls any somInit

code that may have been provided by the class (if somInit was overridden). Because the

generic procedure for somDefaultInit is less efficient than the stub procedure that is

provided when somDefaultInit is overridden, it is recommended that the .idl file always

override somDefaultInit.

Note: It is not appropriate to override both somDefaultInit and somInit. If this is done, the

somInit code will not be executed. The best way to convert an old class that

overrides somInit to use of the more efficient somDefaultInit (if this is desired) is as

follows: (1) Replace the somInit override in the class’s .idl file with an override for

somDefaultInit, (2) run the implementation template emitter to produce a stub

procedure for somDefaultInit, and then (3) simply call the class’s somInit

procedure directly (not using a method invocation) from the somDefaultInit method

procedure.

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