Module: Haml::Filters::Base

### Home Classes Methods

### In Files

- lib/haml/filters.rb

### Methods

- ::included
- #compile
- #internal_compile
- #render
- #render_with_options

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# Haml::Filters::Base

The base module for Haml filters. User-defined filters should be modules including this module. The name of the filter is taken by downcasing the module name. For instance, if the module is named `FooBar`, the filter will be `:foobar`.

A user-defined filter should override either {#render} or {#compile}. {#render} is the most common. It takes a string, the filter source, and returns another string, the result of the filter. For example, the following will define a filter named `:sass`:

    module Haml::Filters::Sass
      include Haml::Filters::Base

      def render(text)
        ::Sass::Engine.new(text).render
      end
    end

For details on overriding {#compile}, see its documentation.

Note that filters overriding {#render} automatically support `#{}` for interpolating Ruby code. Those overriding {#compile} will need to add such support manually if it’s desired.

### Public Class Methods

included(base) click to toggle source

This method is automatically called when {Base} is included in a module. It automatically defines a filter with the downcased name of that module. For example, if the module is named `FooBar`, the filter will be `:foobar`.

@param base [Module, Class] The module that this is included in

    # File lib/haml/filters.rb, line 106
    def self.included(base)
      Filters.defined[base.name.split("::").last.downcase] = base
      base.extend(base)
    end

### Public Instance Methods

compile(compiler, text) click to toggle source

This should be overridden when a filter needs to have access to the Haml evaluation context. Rather than applying a filter to a string at compile-time, {#compile} uses the {Haml::Compiler} instance to compile the string to Ruby code that will be executed in the context of the active Haml template.

Warning: the {Haml::Compiler} interface is neither well-documented nor guaranteed to be stable. If you want to make use of it, you’ll probably need to look at the source code and should test your filter when upgrading to new Haml versions.

@param compiler [Haml::Compiler] The compiler instance @param text [String] The text of the filter @raise [Haml::Error] if none of {#compile}, {#render}, and

    \{#render_with_options} are overridden

    # File lib/haml/filters.rb, line 160
    def compile(compiler, text)
      filter = self
      compiler.instance_eval do
        if contains_interpolation?(text)
          return if options[:suppress_eval]

          text = unescape_interpolation(text).gsub(/(\\+)n/) do |s|
            escapes = $1.size
            next s if escapes % 2 == 0
            ("\\" * (escapes - 1)) + "\n"
          end
          # We need to add a newline at the beginning to get the
          # filter lines to line up (since the Haml filter contains
          # a line that doesn't show up in the source, namely the
          # filter name). Then we need to escape the trailing
          # newline so that the whole filter block doesn't take up
          # too many.
          text = "\n" + text.sub(/\n"\Z/, "\\n\"")
          push_script find_and_preserve(#{filter.inspect}.render_with_options(#{text}, _hamlout.options)).rstrip, :escape_html => false
          return
        end

        rendered = Haml::Helpers::find_and_preserve(filter.render_with_options(text, compiler.options), compiler.options[:preserve])

        if options[:ugly]
          push_text(rendered.rstrip)
        else
          push_text(rendered.rstrip.gsub("\n", "\n#{'  ' * @output_tabs}"))
        end
      end
    end

internal_compile(*args) click to toggle source

Same as {#compile}, but requires the necessary files first. *This is used by {Haml::Engine} and is not intended to be overridden or used elsewhere.*

@see compile

    # File lib/haml/filters.rb, line 140
    def internal_compile(*args)
      compile(*args)
    end

render(text) click to toggle source

Takes the source text that should be passed to the filter and returns the result of running the filter on that string.

This should be overridden in most individual filter modules to render text with the given filter. If {#compile} is overridden, however, {#render} doesn’t need to be.

@param text [String] The source text for the filter to process @return [String] The filtered result @raise [Haml::Error] if it’s not overridden

    # File lib/haml/filters.rb, line 121
    def render(text)
      raise Error.new("#{self.inspect}#render not defined!")
    end

render_with_options(text, options) click to toggle source

Same as {#render}, but takes a {Haml::Engine} options hash as well. It’s only safe to rely on options made available in {Haml::Engine#options_for_buffer}.

@see render @param text [String] The source text for the filter to process @return [String] The filtered result @raise [Haml::Error] if it or {#render} isn’t overridden

    # File lib/haml/filters.rb, line 132
    def render_with_options(text, options)
      render(text)
    end

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