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How do "inline templates" work internally? #7

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ericgj opened this issue Jun 5, 2012 · 3 comments
Open

How do "inline templates" work internally? #7

ericgj opened this issue Jun 5, 2012 · 3 comments

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@ericgj
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ericgj commented Jun 5, 2012

@codereading/readers
@ericgj
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ericgj commented Jun 5, 2012

The Sinatra docs say:

NOTE: Inline templates defined in the source file that requires sinatra are automatically loaded. Call enable :inline_templates explicitly if you have inline templates in other source files.

This is a puzzler: where do the inline templates defined in the source file that requires sinatra get loaded?

Here's the code that runs when you enable :inline_templates . Curious to see that you could also do something like set :inline_templates, 'another_file.rb' .

https://github.com/codereading/sinatra/blob/ver1.3.2/lib/sinatra/base.rb#L1049

      # Load embeded templates from the file; uses the caller's __FILE__
      # when no file is specified.
      def inline_templates=(file=nil)
        file = (file.nil? || file == true) ? (caller_files.first || File.expand_path($0)) : file

        begin
          io = ::IO.respond_to?(:binread) ? ::IO.binread(file) : ::IO.read(file)
          app, data = io.gsub("\r\n", "\n").split(/^__END__$/, 2)
        rescue Errno::ENOENT
          app, data = nil
        end

        if data
          if app and app =~ /([^\n]*\n)?#[^\n]*coding: *(\S+)/m
            encoding = $2
          else
            encoding = settings.default_encoding
          end
          lines = app.count("\n") + 1
          template = nil
          force_encoding data, encoding
          data.each_line do |line|
            lines += 1
            if line =~ /^@@\s*(.*\S)\s*$/
              template = force_encoding('', encoding)
              templates[$1.to_sym] = [template, file, lines]
            elsif template
              template << line
            end
          end
        end
      end

@kgrz
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kgrz commented Jun 6, 2012

Inline templates essentially are written after the entire app is written. For example:

require 'sinatra'
  get '/' do
    erb :index
  end
__END__
@@ index
<html>
 <!-- Some stuff here -->
</html>

A complete example can be found in the chat application under sinatra/examples folder

This is what I understood:

  • The part after __END__ is not executed by Ruby.
  • IO.binread(file) reads the file in binary mode, and splits it into two parts -> app and data. This happens at this step: io.gsub("\r\n", "\n").split(/^__END__$/, 2). The gsub method is called to normalize the line ending differences between different OSes (read CRLF, LF, CR issues) and the split method splits the file at the __END__ keyword into app and data. The data object, essentially contains the inline template info.
  • At line =~ /^@@\s*(.*\S)\s*$/, the inline template "index" specified in the example by @@ index gets matched so that any line after the regex match is considered as a template.

@lyonsinbeta
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I've never seen inline erb before, online inline HAML. This is good to know for when you're writing really small apps, and don't want to use HAML.

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@ericgj @kgrz @lyonsinbeta