Hi Sam, welcome aboard.
On Friday 04 Mar 2011 18:47:40 Sam Steingold wrote: > 1 How do I compare Class::Struct instances (objects) > for equality (or precedence)? > > E.g., > > use Class::Struct MyStruct => > [foo => '$', > bar => '$', > baz => '$']; > > my MyStruct $a = MyStruct->new(foo => "a"); > my MyStruct $b = MyStruct->new(bar => "b"); > my MyStruct $a1 = MyStruct->new(foo => "a"); > First of all I should note that there are better accessor generators already than Class::Struct. see: http://www.shlomifish.org/lecture/Perl/Newbies/lecture5/accessors/ where I recommend either Class-Accessor (simple, sane and popular), Class- XSAccessor (very fast) or Moose (extremely powerful and versatile, but has a small compile-time overhead). Class::Struct should also be OK. To answer your question you can use the or operator for this: http://www.shlomifish.org/lecture/Perl/Newbies/lecture4/and_or/sort.html Moreover, don't call your lexical variables "$a" and "$b" because they are used in sort. > Both ($a eq $a1) and ($a eq $b) return false which is wrong for the > first expression. > I can write my own comparison, of course: > > sub struct_eq ($$) { > my ($x,$y) = @_; > List::AllUtils::notall > (sub { $_ }, (List::AllUtils::pairwise > (sub { $a eq $b }, @$x, @$y))); > } > > but this does simple version does not work because some fields are > undefined and I have to check than and it quickly becomes a nightmare. > I could write a tedious function like > > sub MyStruct_eq ($$) { > my ($x,$y) = @_; > (defined $x->foo and defined $y->foo and $x->foo eq $y->foo) > or (not defined $x->foo and not defined $y->foo) > ..... > } > > but there must be a better way. > > 2. Is there a way to get a list of all fields in a struct? > Class::Fields seems to claim to be able to do it, but I cannot figure > out how to use it. > Class::Fields->show_fields('MyStruct') returns nothing. > MyStruct->show_fields is not defined. > I am lost. > > I would also like to be able to access MyStruct instance fields by name. > I know I can do that using hash{} instead of array[] in the definition, > but I would like to preserve the underlying array structure for passing > to Text::CSV functions (I guess I could use "values" for that too). > E.g., I want to be able to write something like > > my $mystruct_foo_pos = MyStruct->getpos('foo'); > > and have $mystruct_foo_pos set to 0. > then I will be able to write > > my MyStruct $a = MyStruct->new(...); > > $a[$mystruct_foo_pos] = "a"; > You can do it with Moose or friends ( http://www.iinteractive.com/moose/ ) using intropsection. And you should not use arrays references for structs, but hash references, where it is a bit easier. Regards, Shlomi Fish -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ The Case for File Swapping - http://shlom.in/file-swap There is no IGLU Cabal! Home-made Cabals eventually superceded the power and influence of the original IGLU Cabal, which was considered a cutting edge development at its time. Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
