The Rise of “Constructors” and “Accessors” A instantiation, is when a variable is assigned a super-subroutine (class). A variable assigned such a super-subroutine is now called a instance of a class or a object.
In OOP practice, certain inner-subroutines (methods) have developed into specialized purposes. A inner-subroutine that is always called when the super-subroutine is assigned to a variable (instantiation), is called a constructor or initializer. These specialized inner-subroutines are sometimes given a special status in the language. For example in Java the language, constructors are different from methods. In OOP, it has developed into a practice that in general the data inside super-subroutines are supposed to be changed only by the super-subroutine's inner-subroutines, as opposed to by reference thru the super-subroutine. (In OOP parlance: class's variables are supposed to be accessed/changed only by the class's methods.) Though this practice is not universal or absolute. Inner-subroutines that change or return the value of variables are called accessors. For example, in Java, a string class's method length() is a accessor. Because constructors are usually treated as a special method at the language level, its concept and linguistic issues is a OOP machinery complexity, while the Accessor concept is a OOP engineering complexity. ----- to be continued tomorrow. This is part of an installment of the article “What are OOP's Jargons and Complexities” by Xah Lee, 20050128. The full text is at http://xahlee.org/Periodic_dosage_dir/t2/oop.html © Copyright 2005 by Xah Lee. Verbatim duplication of the complete article for non-profit purposes is granted. The article is published in the following newsgroups: comp.lang.c,comp.lang.c++,comp.lang.lisp,comp.unix.programmer comp.lang.python,comp.lang.perl.misc,comp.lang.scheme,comp.lang.java.programmer comp.lang.functional,comp.object,comp.software-eng,comp.software.patterns Xah [EMAIL PROTECTED] ∑ http://xahlee.org/ -- http://mail.python.org/mailman/listinfo/python-list
