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.<<"
compiler.insert_cmd = "_erbout.<<"
compiler.post_cmd   = ["_erbout"]

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

Generates:

#coding:UTF-8
_erbout=+''; _erbout.<< "Got ".freeze; _erbout.<<(( obj ).to_s); _erbout.<< "!\n".freeze; _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 ".freeze; print(( obj ).to_s); print "!\n".freeze

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, 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 694

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 707

def insert_cmd
  @insert_cmd
end

#percentObject (readonly)

Returns the value of attribute percent


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# File 'lib/erb.rb', line 701

def percent
  @percent
end

#post_cmdObject

An array of commands appended to compiled code


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# File 'lib/erb.rb', line 713

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 710

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 704

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 701

def trim_mode
  @trim_mode
end

Instance Method Details

#add_insert_cmd(out, content) ⇒ Object


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# File 'lib/erb.rb', line 576

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 572

def add_put_cmd(out, content)
  out.push("#{@put_cmd} #{content.dump}.freeze#{"\n" * content.count("\n")}")
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 582

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

  self.content = +''
  scanner = make_scanner(s)
  scanner.scan do |token|
    next if token.nil?
    next if token == ''
    if scanner.stag.nil?
      compile_stag(token, out, scanner)
    else
      compile_etag(token, out, scanner)
    end
  end
  add_put_cmd(out, content) if content.size > 0
  out.close
  return out.script, *magic_comment
end

#compile_content(stag, out) ⇒ Object


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# File 'lib/erb.rb', line 642

def compile_content(stag, out)
  case 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 '<%#'    # commented out

  end
end

#compile_etag(etag, out, scanner) ⇒ Object


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# File 'lib/erb.rb', line 629

def compile_etag(etag, out, scanner)
  case etag
  when '%>'
    compile_content(scanner.stag, out)
    scanner.stag = nil
    self.content = +''
  when '%%>'
    content << '%>'
  else
    content << etag
  end
end

#compile_stag(stag, out, scanner) ⇒ Object


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# File 'lib/erb.rb', line 605

def compile_stag(stag, out, scanner)
  case stag
  when PercentLine
    add_put_cmd(out, content) if content.size > 0
    self.content = +''
    out.push(stag.to_s)
    out.cr
  when :cr
    out.cr
  when '<%', '<%=', '<%#'
    scanner.stag = stag
    add_put_cmd(out, content) if content.size > 0
    self.content = +''
  when "\n"
    content << "\n"
    add_put_cmd(out, content)
    self.content = +''
  when '<%%'
    content << '<%'
  else
    content << stag
  end
end

#make_scanner(src) ⇒ Object

:nodoc:


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# File 'lib/erb.rb', line 688

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 659

def prepare_trim_mode(mode) # :nodoc:
  case mode
  when 1
    return [false, '>']
  when 2
    return [false, '<>']
  when 0, nil
    return [false, nil]
  when String
    unless mode.match?(/\A(%|-|>|<>){1,2}\z/)
      warn_invalid_trim_mode(mode, uplevel: 5)
    end

    perc = mode.include?('%')
    if mode.include?('-')
      return [perc, '-']
    elsif mode.include?('<>')
      return [perc, '<>']
    elsif mode.include?('>')
      return [perc, '>']
    else
      [perc, nil]
    end
  else
    warn_invalid_trim_mode(mode, uplevel: 5)
    return [false, nil]
  end
end