Class: ERB::Compiler

Inherits:
Object
  • Object
show all
Defined in:
lib/erb.rb

Overview

ERB::Compiler

Compiles ERB templates into Ruby code; the compiled code produces the template result when evaluated. ERB::Compiler provides hooks to define how generated output is handled.

Internally ERB does something like this to generate the code returned by ERB#src:

compiler = ERB::Compiler.new('<>')
compiler.pre_cmd    = ["_erbout=''"]
compiler.put_cmd    = "_erbout.concat"
compiler.insert_cmd = "_erbout.concat"
compiler.post_cmd   = ["_erbout"]

code, enc = compiler.compile("Got <%= obj %>!\n")
puts code

Generates:

#coding:UTF-8
_erbout=''; _erbout.concat "Got "; _erbout.concat(( obj ).to_s); _erbout.concat "!\n"; _erbout

By default the output is sent to the print method. For example:

compiler = ERB::Compiler.new('<>')
code, enc = compiler.compile("Got <%= obj %>!\n")
puts code

Generates:

#coding:UTF-8
print "Got "; print(( obj ).to_s); print "!\n"

Evaluation

The compiled code can be used in any context where the names in the code correctly resolve. Using the last example, each of these print 'Got It!'

Evaluate using a variable:

obj = 'It'
eval code

Evaluate using an input:

mod = Module.new
mod.module_eval %{
  def get(obj)
    #{code}
  end
}
extend mod
get('It')

Evaluate using an accessor:

klass = Class.new Object
klass.class_eval %{
  attr_accessor :obj
  def initialize(obj)
    @obj = obj
  end
  def get_it
    #{code}
  end
}
klass.new('It').get_it

Good! See also ERB#def_method, ERB#def_module, and ERB#def_class.

Defined Under Namespace

Classes: Buffer, PercentLine, Scanner, SimpleScanner, TrimScanner

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(trim_mode) ⇒ Compiler

Construct a new compiler using the trim_mode. See ERB::new for available trim modes.


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# File 'lib/erb.rb', line 692

def initialize(trim_mode)
  @percent, @trim_mode = prepare_trim_mode(trim_mode)
  @put_cmd = 'print'
  @insert_cmd = @put_cmd
  @pre_cmd = []
  @post_cmd = []
end

Instance Attribute Details

#insert_cmdObject

The command to handle text that is inserted prior to a newline


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# File 'lib/erb.rb', line 705

def insert_cmd
  @insert_cmd
end

#percentObject (readonly)

Returns the value of attribute percent


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# File 'lib/erb.rb', line 699

def percent
  @percent
end

#post_cmdObject

An array of commands appended to compiled code


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# File 'lib/erb.rb', line 711

def post_cmd
  @post_cmd
end

#pre_cmdObject

An array of commands prepended to compiled code


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# File 'lib/erb.rb', line 708

def pre_cmd
  @pre_cmd
end

#put_cmdObject

The command to handle text that ends with a newline


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# File 'lib/erb.rb', line 702

def put_cmd
  @put_cmd
end

#trim_modeObject (readonly)

Returns the value of attribute trim_mode


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# File 'lib/erb.rb', line 699

def trim_mode
  @trim_mode
end

Instance Method Details

#add_insert_cmd(out, content) ⇒ Object


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# File 'lib/erb.rb', line 591

def add_insert_cmd(out, content)
  out.push("#{@insert_cmd}((#{content}).to_s)")
end

#add_put_cmd(out, content) ⇒ Object


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# File 'lib/erb.rb', line 587

def add_put_cmd(out, content)
  out.push("#{@put_cmd} #{content_dump(content)}")
end

#compile(s) ⇒ Object

Compiles an ERB template into Ruby code. Returns an array of the code and encoding like [“code”, Encoding].

Raises:

  • (ArgumentError)

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# File 'lib/erb.rb', line 597

def compile(s)
  enc = s.encoding
  raise ArgumentError, "#{enc} is not ASCII compatible" if enc.dummy?
  s = s.b # see String#b
  enc = detect_magic_comment(s) || enc
  out = Buffer.new(self, enc)

  content = ''
  scanner = make_scanner(s)
  scanner.scan do |token|
    next if token.nil?
    next if token == ''
    if scanner.stag.nil?
      case token
      when PercentLine
        add_put_cmd(out, content) if content.size > 0
        content = ''
        out.push(token.to_s)
        out.cr
      when :cr
        out.cr
      when '<%', '<%=', '<%#'
        scanner.stag = token
        add_put_cmd(out, content) if content.size > 0
        content = ''
      when "\n"
        content << "\n"
        add_put_cmd(out, content)
        content = ''
      when '<%%'
        content << '<%'
      else
        content << token
      end
    else
      case token
      when '%>'
        case scanner.stag
        when '<%'
          if content[-1] == ?\n
            content.chop!
            out.push(content)
            out.cr
          else
            out.push(content)
          end
        when '<%='
          add_insert_cmd(out, content)
        when '<%#'
          # out.push("# #{content_dump(content)}")
        end
        scanner.stag = nil
        content = ''
      when '%%>'
        content << '%>'
      else
        content << token
      end
    end
  end
  add_put_cmd(out, content) if content.size > 0
  out.close
  return out.script, enc
end

#content_dump(s) ⇒ Object

:nodoc:


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# File 'lib/erb.rb', line 578

def content_dump(s) # :nodoc:
  n = s.count("\n")
  if n > 0
    s.dump + "\n" * n
  else
    s.dump
  end
end

#make_scanner(src) ⇒ Object

:nodoc:


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# File 'lib/erb.rb', line 686

def make_scanner(src) # :nodoc:
  Scanner.make_scanner(src, @trim_mode, @percent)
end

#prepare_trim_mode(mode) ⇒ Object

:nodoc:


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# File 'lib/erb.rb', line 662

def prepare_trim_mode(mode) # :nodoc:
  case mode
  when 1
    return [false, '>']
  when 2
    return [false, '<>']
  when 0
    return [false, nil]
  when String
    perc = mode.include?('%')
    if mode.include?('-')
      return [perc, '-']
    elsif mode.include?('<>')
      return [perc, '<>']
    elsif mode.include?('>')
      return [perc, '>']
    else
      [perc, nil]
    end
  else
    return [false, nil]
  end
end