On Jun 2, Matthew Sacks said:
When you invoke a method, the first argument to the method equal to the
method's invocant is automatically inserted.
That sounds about right. The first argument to a method is either a class
name or the object, depending on whether it's a class method or an object
method:
my $foo = SomeClass->new('blah');
The arguments to the 'new' method are ('SomeClass', 'blah').
$foo->some_method(10, 50);
The arguments to the 'some_method' method are ($foo, 10, 50).
i) Is this essentially the same as a C++ "this" pointer?
Yes; the first argument to an object method is the object, which is
synonymous to the 'this' pointer in C++.
ii) Apparently, the first argument can be a reference to its object, or
the object.
Uh, that sounds wrong. Objects *are* references in Perl, just a special
kind of reference. An object is a reference that has been "blessed" into
a particular package/class/namespace:
package SomeClass;
sub new {
my $pkg = shift;
# $pkg is the class to bless into... it is not
# NECESSARILY SomeClass, because a class could
# be inheriting its new() method from SomeClass
my $obj = bless [EMAIL PROTECTED], $pkg;
return $obj;
}
A reference to an object is not necessarily an object. That is:
$foo->some_method(...);
works, but
my $ref_to_foo = \$foo;
$ref_to_foo->some_method(...);
does NOT work.
iii) There is an example in the Camel book, in the
Object-Oriented-Programming Chapter (ch. 12), where accessor methods are
being generated automatically; in this example, it seems that the
invocant is explicity placed into the first argument. If you put in the
this pointer, does PERL know not to put in another one?
I don't have my Camel at hand. Is this an AUTOLOADing issue?
--
Jeff "japhy" Pinyan % How can we ever be the sold short or
RPI Acacia Brother #734 % the cheated, we who for every service
http://japhy.perlmonk.org/ % have long ago been overpaid?
http://www.perlmonks.org/ % -- Meister Eckhart
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