# class Builder::XmlBase

XmlBase is a base class for building XML builders. See Builder::XmlMarkup and Builder::XmlEvents for examples.

### Attributes

cache_method_calls[RW]

### Public Class Methods

new(indent=0, initial=0, encoding='utf-8') click to toggle source

Create an XML markup builder.

out

  Object receiving the markup. `out` must respond to `<<`.

indent

  Number of spaces used for indentation (0 implies no indentation and no line breaks).

initial

  Level of initial indentation.

encoding

  When `encoding` and $KCODE are set to 'utf-8' characters aren't converted to character entities in the output stream.

    # File lib/builder/xmlbase.rb, line 28
    def initialize(indent=0, initial=0, encoding='utf-8')
      @indent = indent
      @level  = initial
      @encoding = encoding.downcase
    end

### Public Instance Methods

<<(text) click to toggle source

Append text to the output target without escaping any markup. May be used within the markup brackets as:

    builder.p { |x| x << "<br/>HI" }   #=>  <p><br/>HI</p>

This is useful when using non-builder enabled software that generates strings. Just insert the string directly into the builder without changing the inserted markup.

It is also useful for stacking builder objects. Builders only use `<<` to append to the target, so by supporting this method/operation builders can use other builders as their targets.

    # File lib/builder/xmlbase.rb, line 117
    def <<(text)
      _text(text)
    end

explicit_nil_handling?() click to toggle source

    # File lib/builder/xmlbase.rb, line 34
    def explicit_nil_handling?
      @explicit_nil_handling
    end

method_missing(sym, *args, &block) click to toggle source

Create XML markup based on the name of the method. This method is never invoked directly, but is called for each markup method in the markup block that isn't cached.

    # File lib/builder/xmlbase.rb, line 91
    def method_missing(sym, *args, &block)
      cache_method_call(sym) if ::Builder::XmlBase.cache_method_calls
      tag!(sym, *args, &block)
    end

nil?() click to toggle source

For some reason, nil? is sent to the XmlMarkup object. If nil? is not defined and #method_missing is invoked, some strange kind of recursion happens. Since nil? won't ever be an XML tag, it is pretty safe to define it here. (Note: this is an example of cargo cult programming, cf. fishbowl.pastiche.org/2004/10/13/cargo_cult_programming).

    # File lib/builder/xmlbase.rb, line 127
    def nil?
      false
    end

tag!(sym, *args, &block) click to toggle source

Create a tag named `sym`. Other than the first argument which is the tag name, the arguments are the same as the tags implemented via `method_missing`.

    # File lib/builder/xmlbase.rb, line 41
    def tag!(sym, *args, &block)
      text = nil
      attrs = nil
      sym = "#{sym}:#{args.shift}" if args.first.kind_of?(::Symbol)
      sym = sym.to_sym unless sym.class == ::Symbol
      args.each do |arg|
        case arg
        when ::Hash
          attrs ||= {}
          attrs.merge!(arg)
        when nil
          attrs ||= {}
          attrs.merge!({:nil => true}) if explicit_nil_handling?
        else
          text ||= ''
          text << arg.to_s
        end
      end
      if block
        unless text.nil?
          ::Kernel::raise ::ArgumentError,
            "XmlMarkup cannot mix a text argument with a block"
        end
        _indent
        _start_tag(sym, attrs)
        _newline
        begin
          _nested_structures(block)
        ensure
          _indent
          _end_tag(sym)
          _newline
        end
      elsif text.nil?
        _indent
        _start_tag(sym, attrs, true)
        _newline
      else
        _indent
        _start_tag(sym, attrs)
        text! text
        _end_tag(sym)
        _newline
      end
      @target
    end

text!(text) click to toggle source

Append text to the output target. Escape any markup. May be used within the markup brackets as:

    builder.p { |b| b.br; b.text! "HI" }   #=>  <p><br/>HI</p>

    # File lib/builder/xmlbase.rb, line 100
    def text!(text)
      _text(_escape(text))
    end

### Private Instance Methods

_escape(text) click to toggle source

    # File lib/builder/xmlbase.rb, line 135
    def _escape(text)
      result = XChar.encode(text)
      begin
        encoding = ::Encoding::find(@encoding)
        raise Exception if encoding.dummy?
        result.encode(encoding)
      rescue
        # if the encoding can't be supported, use numeric character references
        result.
          gsub(/[^\u0000-\u007F]/) {|c| "&##{c.ord};"}.
          force_encoding('ascii')
      end
    end

_escape_attribute(text) click to toggle source

    # File lib/builder/xmlbase.rb, line 158
    def _escape_attribute(text)
      _escape(text).gsub("\n", "&#10;").gsub("\r", "&#13;").
        gsub(%r{"}, '&quot;') # " WART
    end

_indent() click to toggle source

    # File lib/builder/xmlbase.rb, line 168
    def _indent
      return if @indent == 0 || @level == 0
      text!(" " * (@level * @indent))
    end

_nested_structures(block) click to toggle source

    # File lib/builder/xmlbase.rb, line 173
    def _nested_structures(block)
      @level += 1
      block.call(self)
    ensure
      @level -= 1
    end

_newline() click to toggle source

    # File lib/builder/xmlbase.rb, line 163
    def _newline
      return if @indent == 0
      text! "\n"
    end

cache_method_call(sym) click to toggle source

If ::cache_method_calls = true, we dynamicly create the method missed as an instance method on the XMLBase object. Because XML documents are usually very repetative in nature, the next node will be handled by the new method instead of method_missing. As #method_missing is very slow, this speeds up document generation significantly.

    # File lib/builder/xmlbase.rb, line 186
    def cache_method_call(sym)
      class << self; self; end.class_eval do
        unless method_defined?(sym)
          define_method(sym) do |*args, &block|
            tag!(sym, *args, &block)
          end
        end
      end
    end