Hi Graeme
(I repost this email too to the list, this way somebody can correct me)
> Re: returning a hash from a method call ?
> Datum: Heute 21.08:32
> Von: "Graeme McLaren" <[EMAIL PROTECTED]>
> An: [EMAIL PROTECTED]
>
> Hey Joe, thank you for your reply, what you said all makes sense and I like
> the idea of setting all of the conf data during object creation.
>
> Could I simply put "$self->{conf}={table=>'blog',...};" in the constructor
> before it is returned then use your sub?
...to access $self->{conf}, yes
(another question is the interface of such a class)
> sub get_users_table_and_columns{
> return $_[0]->{conf};
> }
>
>
> As nothing is being passed to the method "get_users_table_and_columns" would
> the equivalent of $_[0] be exactly the same as my $self=shift; ?
Not exactly; $_[0] is the first element of @_ (the arguments passed to the
method) without retrieving it from @_.
This same first element is contained in $self after "$self=shift", shift
retrieving the first element from @_. See
perldoc -f shift
.
When calling a method of an object, like
$obj->get_users_table_and_columns;
$obj is passed implicitly to the method as first argument. Above call is
similar to get_users_table_and_columns($obj).
> I think that way would be a good way of doing it as it provides some
> indirection through an accessor/mutator function.
Yes, best access/change object attributes only by methods, not directly.
> The way I was thinking of doing it I wanted to have a sub that would return
> a hash which I could then pass to another function to make use of the data.
> Why would I only have one key of the hash printed out when I do:
>
> my $conf=configuration->new;
> die Dumper($conf->get_users_table_and_columns);
Don't know...
> Thanks again for your reply and advice you can give me would be great.
> Here's the full module.
I'll try to comment this module in detail as it is, and provide a possible
alternative.
> Cheers,
>
> Graeme :)
>
> ################## start of module #########################
> #configuration.pm
> package configuration;
> use strict;
use warnings; # additionaly
> sub new{
> my $class=shift;
> my $self={};
> bless($self, $class);
> return $self->conf;
A new() class method ("class method" because not an object, but a class name
is passed als first argument) should return the created object, $self, not
the configuration values:
return $self; # instead of return $self->conf;
(You would call $self->conf after having an object:
my $obj=configuration->new(); # create object
my %conf=$obj->conf; # call object method
)
The two different %conf contents from below can be put into the object as
object attributes:
sub new
my $class=shift;
# more params could be provided, e.g. for initializing the attributes
my $self={
host => "host",
db_name=>"db_name",
username=>"username",
tab_cols_config=>{
table=>'blog',
column1 =>'first_name',
}, # etc.
};
return bless $self, $class;
}
> }
>
> sub conf{
> my $self=shift;
> my %conf=(
> host => "host",
> db_name=>"db_name",
> username=>"username",
> password=>"password",
>
> ## templates
> registration_form => "/var/www/templates/registration.tmpl"
> );
>
> foreach my $k ( keys %conf ) {
> $self->{$k} = $conf{$k};
> }
> return $self;
Here, you should return the configuration values, not the object.
However, the question is if you don't want to provide the methods
sub host { $_[0]->{host} };
sub dbname # etc.
sub username
sub password
sub registration_form
# and, see below,
sub tab_cols_config
instead of conf() and the following get_key().
>
> }
>
> sub get_key{
> my $self = shift;
> my $key = shift;
> return $self->{$key};
> }
This could be an alternative to the proposed 6 subs, but does, as implemented,
not add much additional abstraction over the direct read access of the object
attributes. At least, get_key() could test if a certain attribute exists and
can be accessed:
return exists ($self->{$key}) ? $self->{$key} : undef;
> sub get_users_table_and_columns{
> my $self=shift;
>
> my %conf=(
> table=>'blog',
> column1 =>'first_name',
> column2 => 'last_name',
> column3 => 'email',
> column4 => 'password',
> column5 => 'active'
> );
>
>
> return \%conf;
>
> }
# returns hashref
sub get_users_table_and_columns{
$_[0]->{tab_cols_config};
}
There are other possibilities like a separate class for the tab_cols_config
data if there are many table configs...
> 1;
Maybe the class is a bit overkill, who knows :-)
>
> ################## End of Module ##########################
>
>
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