Customizing erb's recognized tags

Ruby
1

Hi

Does anyone know if it’s possible to change the tags that erb
recognizes so that for instance, I can have it replace on #{} instead
of <%= %> ?

If so, could you point me an example of how it’s done?

thanks.

thanks

2

On Dec 9, 2005, at 7:46 PM, Larry W. wrote:

Hi

Does anyone know if it’s possible to change the tags that erb
recognizes so that for instance, I can have it replace on #{} instead
of <%= %> ?

You mean normal String interpolation?

str = <<‘END’
I have a #{2 - 1} line string here!
END
=> “I have a #{2 - 1} line string here!\n”

eval %Q{"#{str}"}
=> “I have a 1 line string here!\n”

James Edward G. II

3

I need to read in a template file and apply replacements in two steps

  • so i can’t use the same tags for each pass.

I don’t think string interpolation works on strings read from files
which are single quoted by default. If there’s a way around that it
might be ok.

4

i want to do a series of replacements on a file in two passes - one at
‘compile time’, one at runtime. For a simple example, if i’m
creating 2 copies of a dynamic web page - one for each of two tables -
i would replace references to the table at ‘compile time’ and display
the particular values of a record from the table at runtime.It might
look like this

<% for column in #{table_name}.display_columns %> <%= column.name %> <% end %>

So i want to replace #{table_name} in the first pass and the rest of
the stuff in the second pass. Since there could be a large number of
replacements at either time, I thought a solution using erb with
different tag sets might be reasonably maintainable.

thanks for your help.

5

Larry W. wrote:

Hi

Does anyone know if it’s possible to change the tags that erb
recognizes so that for instance, I can have it replace on #{} instead
of <%= %> ?

If so, could you point me an example of how it’s done?

I wrote a hack that overrides IO.read. When IO grabs the file, it
checks the file extension; if it’s an erb template, it replaces <? ?>
(with some variants) markup with <% %> before passing along the content.

It was a Good Enough sort of thing for the circumstances.

class IO
class <<self
alias real_read read
end

def IO.read( *args )
return IO.real_read( *args ) unless args[0].to_s =~ /.rhtml/i
text = IO.real_read( *args )
s = ‘’
text.each_line( ) { |l|
next if l =~ /<?xml/ l.gsub!( '<?eq', '<%=') l.gsub!( '<? ', '<% ') l.gsub!( '?>', ‘%>’)
s << “#{l}\n”
}
s
end
end

James

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6

On Dec 9, 2005, at 8:58 PM, Larry W. wrote:

<% end %>

So i want to replace #{table_name} in the first pass and the rest of
the stuff in the second pass. Since there could be a large number of
replacements at either time, I thought a solution using erb with
different tag sets might be reasonably maintainable.

My example pretty much works for that, with minor tweaks:

template = <<‘END’

<% for column in #{table_name}.display_columns %> <%= column.name %> <% end %> END => "\n <% for column in \#{table_name}.display_columns %>\n <%= column.name %>\n <% end %>\n\n" >> table = Object.new => # >> class <> def display_columns >> names = %w{col_one col_two col_three} >> end >> end => nil >> class String >> def name; self end >> end => nil >> table_name = "table" => "table" >> template = eval(%Q{"#{template.gsub('"', '\\"')}"}, binding) => "\n <% for column in table.display_columns %>\n <%= column.name %>\n <% end %>\n\n" >> require "erb" => true >> ERB.new(template).result(binding) => "\n \n col_one\n \n col_two\n \n col_three\n \n\n"

I wouldn’t do it though. What’s the harm of sticking the table name
in a variable each tim before you run the template through ERb?
Heck, run the templates like this:

ERB.new(template).result(table.instance_eval { binding })

And then just call display_columns directly.

Hope the helps.

James Edward G. II

7

that might be a good solution. i’ll give it a try. thanks.

8

On Dec 9, 2005, at 8:33 PM, Larry W. wrote:

I need to read in a template file and apply replacements in two steps

  • so i can’t use the same tags for each pass.

I don’t think string interpolation works on strings read from files
which are single quoted by default. If there’s a way around that it
might be ok.

I just showed how to use delayed String interpolation on any String.
My example was single quoted.

Perhaps I don’t understand the question. Can you post a trivial
example of what you want to work?

James Edward G. II