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Re: Perl semi-object without a constructor

by sundialsvc4 (Abbot)
on Feb 21, 2013 at 14:50 UTC ( #1019955=note: print w/replies, xml ) Need Help??

in reply to Perl semi-object without a constructor

Let me try to toss-in an explanation of the big picture here:

(1)   In Perl, an “object” is (usually...) a hashref that has been passed to the built-in function, bless, which takes as its (usually...) two parameters the hashref to be blessed and a package name.   Internally, Perl now flips a switch that says that it is “blessed,” and associates the specified package-name with it.   (Yes, it can be, and occasionally is, re-blessed, which changes the associated package-name.)

Any piece of code which serves this function, no matter where it is located nor what it is named, serves this purpose.   Specifically, there is nothing “magical” about a function named new.

(2)   When something has been blessed, it becomes possible to use the $obj->methodname(args...) syntax.   This simply translates to a subroutine call, to a sub (maybe...) found in the previously-associated package, but passing $obj as an additional, first, parameter.

You will therefore find that these subroutines begin with a statement such as my $self = shift;, which grabs that first-parameter that has been added.   Once again, the name $self is simply a convention.

HTH...   If you are used to looking at very formal, computer-science-y language implementations, you might be a bit startled by Perl.

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