Thanks for everyone's help so far. Sorry for not being clear originally
but it's not that I want alternatives to using replace - I know there's
plenty of better solutions for the small example I gave - it's that I
wanted to know if there was some trick to escaping $ (and possibly other
operators) so the second argument is taken at "face value". I'm pretty
sure I have to use replace in the real world problem I have (basically a
search and replace on manually inserted placeholders within text).
Looks like I'll make a vmethod for quotemeta. Was just hoping I could
fix this small problem without needing to edit the API!
Cheers all.
On 21/04/2010 19:29, Andy Wardley wrote:
> Travis Basevi wrote:
> > Yes, I know that solution,
>
> Sorry, I totally missed that in your original message.
>
> > but lets say the text comes from a database
> > or some other source rather than being hardcoded in the template. Is
> > there a more general/correct solution than something along the lines of:
> >
> > b.replace('_err_', a.replace('$','\$'));
>
> Ah, I see. I thought that was easy work for $50 million!
>
> I think Dave's got it right in terms of counting the backslashes.
>
> b.replace('_err_', a.replace('$','\\\$'));
>
> But I would be inclined to add a custom virtual method that does it all
> in Perl space. I typically use '.format' for this kind of thing:
>
> package My::Template;
> use base 'Template';
>
> sub new {
> my $class = shift;
> my $self = $class->SUPER::new(@_);
> my $context = $self->context;
>
> $context->define_vmethod(
> item => format => sub {
> sprintf($_[1], $_[0])
> }
> );
>
> return $self;
> }
>
> package main;
> my $tt = My::Template->new(...);
> ...etc...
>
> Then you can write:
>
> [% a = 'this problem will cost me $50 million to fix';
> b = 'WARNING: %s';
> a.format(b);
> %]
>
> I recall going to add this as a core virtual method at some point in
> the past, but I couldn't decide if it made more sense as b.format(a)
> or a.format(b). I guess I must have stalled before reaching any
> decision.
>
> Now that I look at it again, I think it makes more sense as b.format(a),
> otherwise you're limited to only one argument. But for that matter, it
> should probably just be called .sprintf
>
> [% format = "hello %s, the time is %s on %s";
> format.sprintf(username, time, date)
> %]
>
> Then the implementation is even simpler:
>
> $context->define_vmethod(
> item => format => sub {
> sprintf(shift, @_)
> }
> );
>
> The other possibility is to use the existing format filter.
>
> [% a | format(b) %]
>
> But be warned that it's a line-oriented filter so if your 'a' has any
> newlines in it then the filter will be applied to each line:
>
> [% a = "Oh Noes!\nThis will cost me $50 million to fix";
> b = "WARNING: %s";
> a | format(b);
> %]
>
> This will output:
>
> WARNING: Oh Noes!
> WARNING: This will cost me $50 million to fix
>
> HTH
> A
>
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