Class: Nanoc::Filter Abstract

Inherits:
Int::Context
  • Object
show all
Defined in:
lib/nanoc/base/compilation/filter.rb

Overview

This class is abstract.

Subclass and override #run to implement a custom filter.

Nanoc::Filter is responsible for filtering items. It is the superclass for all textual filters.

A filter instance should only be used once. Filters should not be reused since they store state.

When creating a filter with a hash containing assigned variables, those variables will be made available in the @assigns instance variable and the #assigns method. The assigns itself will also be available as instance variables and instance methods.

Examples:

Accessing assigns in different ways


filter = SomeFilter.new({ :foo => 'bar' })
filter.instance_eval { @assigns[:foo] }
  # => 'bar'
filter.instance_eval { assigns[:foo] }
  # => 'bar'
filter.instance_eval { @foo }
  # => 'bar'
filter.instance_eval { foo }
  # => 'bar'

Constant Summary

Class Method Summary (collapse)

Instance Method Summary (collapse)

Class Method Details

+ (void) requires(*requires) + (Enumerable<String>) requires

Overloads:

  • + (void) requires(*requires)

    This method returns an undefined value.

    Sets the required libraries for this filter.

    Parameters:

    • requires (Array<String>) —

      A list of library names that are required

  • + (Enumerable<String>) requires

    Returns the required libraries for this filter.

    Returns:

    • (Enumerable<String>) —

      This filter’s list of library names that are required



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# File 'lib/nanoc/base/compilation/filter.rb', line 90

def requires(*requires)
  if requires.any?
    @requires = requires
  else
    @requires || []
  end
end

+ (void) type(arg)

This method returns an undefined value.

Sets the new type for the filter. The type can be :binary (default) or :text. The given argument can either be a symbol indicating both “from” and “to” types, or a hash where the only key is the “from” type and the only value is the “to” type.

Examples:

Specifying a text-to-text filter


type :text

Specifying a text-to-binary filter


type :text => :binary

Parameters:

  • arg (Symbol, Hash) —

    The new type of this filter



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# File 'lib/nanoc/base/compilation/filter.rb', line 57

def type(arg)
  if arg.is_a?(Hash)
    @from = arg.keys[0]
    @to = arg.values[0]
  else
    @from = arg
    @to = arg
  end
end

Instance Method Details

- (void) depend_on(items)

This method returns an undefined value.

Creates a dependency from the item that is currently being filtered onto the given collection of items. In other words, require the given items to be compiled first before this items is processed.



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# File 'lib/nanoc/base/compilation/filter.rb', line 185

def depend_on(items)
  orig_items = items
  items = items.map { |i| i.is_a?(Nanoc::ItemWithRepsView) ? i.unwrap : i }

  # Notify
  items.each do |item|
    Nanoc::Int::NotificationCenter.post(:visit_started, item)
    Nanoc::Int::NotificationCenter.post(:visit_ended,   item)
  end

  # Raise unmet dependency error if necessary
  items.each do |item|
    rep = orig_items.sample._context.reps[item].find { |r| !r.compiled? }
    raise Nanoc::Int::Errors::UnmetDependency.new(rep) if rep
  end
end

- (String) output_filename

Returns a filename that is used to write data to. This method is only used on binary items. When running a binary filter on a file, the resulting file must end up in the location returned by this method.

The returned filename will be absolute, so it is safe to change to another directory inside the filter.

Returns:

  • (String) —

    The output filename



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# File 'lib/nanoc/base/compilation/filter.rb', line 159

def output_filename
  @output_filename ||=
    Nanoc::Int::TempFilenameFactory.instance.create(TMP_BINARY_ITEMS_DIR)
end

- (String, void) run(content_or_filename, params = {})

This method is abstract.

Runs the filter on the given content or filename.

Parameters:

  • content_or_filename (String) —

    The unprocessed content that should be filtered (if the item is a textual item) or the path to the file that should be filtered (if the item is a binary item)

  • params (Hash) (defaults to: {}) —

    A hash containing parameters. Filter subclasses can use these parameters to allow modifying the filter’s behaviour.

Returns:

  • (String, void) —

    If the filter output binary content, the return value is undefined; if the filter outputs textual content, the return value will be the filtered content.

Raises:

  • (NotImplementedError) 


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# File 'lib/nanoc/base/compilation/filter.rb', line 147

def run(content_or_filename, params = {}) # rubocop:disable Lint/UnusedMethodArgument
  raise NotImplementedError.new('Nanoc::Filter subclasses must implement #run')
end