[Bioperl-l] Re: Automatic generation of set and get methods

[Steve Chervitz]

I inadvertantly sent off my last post before I was done typing. Here's the
complete version of the autogenerated set/get accessor with the built in throw
call if validation fails:

--- Steve Chervitz <stevechervitz@yahoo.com> wrote:

[ snip ]
 
Then you hand-code the sub validate_<field> methods to do all the checking
you desire. We could autogenerate the throw call on validation failure if 
we specify that the validate method should return nothing on success and a
string on failure explaining the reason for failure:
 
 *$func =
    sub {
       my $self = shift;
       my $current = $self->{$field};
       if(@_) {
          $self->{$field} = shift;
          if( $self->can("validate_$field") ) {
             if( my $msg = $self->validate_$field ) {
                $self->throw(-text=>$msg,
                             -class=>'Bio::Root::BadParameter',
                             -value=>$field);
             }          
          }
       }
       return $current;
    }

With this version, the module developer gets a fair amount of functionality for
free and can focus on the logic necessary for validating the field's value
within their hand-coded validate_<field> method. If it doesn't validate, just
return a string explaining why, along with what values are acceptable.

You'll note that I'm using the "set returns previous value" policy. My sense is
that most existing code which relies on the return value from setters assumes
it is the previous value, so if our autogenerated code does this, it's less
likely to break existing code.

Steve




=====
Steve Chervitz
sac@bioperl.org

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