in reply to Re: Multiple "constructors", possible to call several.
in thread Multiple "constructors", possible to call several.
Actually, I did look at UNIVERSAL::isa(), but I didn't get that to work properly. Matter of factly, your code is very much like I started to write it - and your code breaks my testcases for this. This is what I get from them:
And these are the very simple testcases:1..11 Testing to construct via 'start_stuff()' Can't use string ("MyClass") as a HASH ref while "strict refs" in use +at MyClass.pm line 61 (#1) (F) Only hard references are allowed by "strict refs". Symbolic references are disallowed. See perlref. Uncaught exception from user code: Can't use string ("MyClass") as a HASH ref while "strict refs" + in use at MyClass.pm line 61. MyClass::start_stuff('MyClass') called at testmyclass.pl line +10
So my question now is, are my testcases faulty? I would bet on that, since I am no expert at this, but no matter how I tried, I concluded that UNIVERSAL::isa() did not work.#!/usr/bin/perl -w use strict; use Test; BEGIN { plan tests => 11 }; use MyClass; print "Testing to construct via 'start_stuff()'\n"; my $object_via_start = MyClass->start_stuff(); ok( ref( $object_via_start ), 'MyClass' ); ok( UNIVERSAL::isa( $object_via_start, 'MyClass' )); print "Testing to construct via 'init_stuff()'\n"; my $object_via_init = MyClass->init_stuff(); ok( ref( $object_via_init ), 'MyClass' ); ok( UNIVERSAL::isa( $object_via_init , 'MyClass' )); print "Testing to invoke 'start_stuff()' and 'use_stuff()' \n"; print "via object from 'init_stuff()'\n"; print "(Should not return a new object).\n"; my $start_stuff_after_init = $object_via_init->start_stuff(); my $start_stuff_after_use = $object_via_init->use_stuff(); ok( ref( $start_stuff_after_init ), 'MyClass' ); ok( UNIVERSAL::isa( $start_stuff_after_init , 'MyClass' )); ok( ref( $start_stuff_after_use ), 'MyClass' ); ok( UNIVERSAL::isa( $start_stuff_after_use , 'MyClass' )); ok( $object_via_init, $start_stuff_after_init ); ok( $object_via_init, $start_stuff_after_use ); ok( $start_stuff_after_init, $start_stuff_after_use );
But this might be why that approach doesn't work. From the docs of UNIVERSAL:
UNIVERSAL::isa ( VAL, TYPE )
isa returns true if one of the following statements is true.
The last point there being the catch. Since, when invoked for the first time, VAL will indeed be "MyClass" (the string). Which is what throws the exception you see above.
This did indeed bother me, so any ideas on why this is happening, or what I am doing wrong, or how I could redesign, would still be helpful.
Minor detail: Due to the way my constructor was finally written, it was well possible to fall off the end, that is why return undef was at the end.