Class: Macros4Cuke::TemplateEngine

Inherits:
Object
  • Object
show all
Defined in:
lib/macros4cuke/template-engine.rb

Overview

A very simple implementation of a templating engine.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(aSourceTemplate) ⇒ TemplateEngine

Constructor.

aSourceTemplate

the template source text. It may contain zero or tags enclosed between chevrons <…>.



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# File 'lib/macros4cuke/template-engine.rb', line 63

def initialize(aSourceTemplate)
  @source = aSourceTemplate
  @representation = compile(aSourceTemplate)
end

Instance Attribute Details

#source ⇒ Object (readonly)

The original text of the template is kept here.



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# File 'lib/macros4cuke/template-engine.rb', line 59

def source
  @source
end

Class Method Details

.parse(aTextLine) ⇒ Object

Class method. Parse the given line text. Returns an array of couples. Couples are of the form:

:static, text

or [:dynamic, text]



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# File 'lib/macros4cuke/template-engine.rb', line 97

def self.parse(aTextLine)
  scanner = StringScanner.new(aTextLine)
  result = []
  
  until scanner.eos?
    # Scan tag at current position...
    tag_literal = scanner.scan(/<(?:[^\\<>]|\\.)*>/)
    result << [:dynamic, tag_literal.gsub(/^<|>$/, '')] unless tag_literal.nil?
    
    # ... or scan plain text at current position
    text_literal = scanner.scan(/(?:[^\\<>]|\\.)+/)
    result << [:static, text_literal] unless text_literal.nil?
    
    if tag_literal.nil? && text_literal.nil?
      # Unsuccessful scanning: we have improperly balanced chevrons.
      # We will analyze the opening and closing chevrons...
      no_escaped = aTextLine.gsub(/\\[<>]/, "--")  # First: replace escaped chevron(s)
      unbalance = 0 # = count of < -  count of > (can only be 0 or -temporarily- 1)

      no_escaped.scan(/(.)/) do |match|
        case match[0]
          when '<'
            unbalance += 1 
          when '>'  
            unbalance -= 1              
        end
        
        raise StandardError, "Nested opening chevron '<'." if unbalance > 1
        raise StandardError, "Missing opening chevron '<'." if unbalance < 0
      end
      
      raise StandardError, "Missing closing chevron '>'." if unbalance == 1
      raise StandardError, "Cannot parse:\n'#{aTextLine}'"
    end
  end
  
  return result
end

Instance Method Details

#render(aContextObject = nil, theLocals) ⇒ Object

aContextObject

context object to get actual values (when not present in the Hash parameter).

theLocals

a Hash with pairs of the form: argument name => actual value.



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# File 'lib/macros4cuke/template-engine.rb', line 71

def render(aContextObject = nil, theLocals)
  return '' if @representation.empty?
  context = aContextObject.nil? ? Object.new : aContextObject
  
  result = @representation.each_with_object('') do |element, subResult|
    subResult << element.render(context, theLocals)
  end
  
  return result
end

#variables ⇒ Object

Return all variable names that appear in the template.



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# File 'lib/macros4cuke/template-engine.rb', line 83

def variables()
  # The result will be cached/memoized...
  @variables ||= begin
    vars = @representation.select { |element| element.is_a?(VariableRep) }
    vars.map(&:name)
  end
  
  return @variables
end