class ERB

Constructs a new ERB object with the template specified in str.

An ERB object works by building a chunk of Ruby code that will output the completed template when run. If safe_level is set to a non-nil value, ERB code will be run in a separate thread with $SAFE set to the provided level.

If trim_mode is passed a String containing one or more of the following modifiers, ERB will adjust its code generation as listed:

%  enables Ruby code processing for lines beginning with %
<> omit newline for lines starting with <% and ending in %>
>  omit newline for lines ending in %>
-  omit blank lines ending in -%>

eoutvar can be used to set the name of the variable ERB will build up its output in. This is useful when you need to run multiple ERB templates through the same binding and/or when you want to control where output ends up. Pass the name of the variable to be used inside a String.

Example¶ ↑

require "erb"

# build data class
class Listings
  PRODUCT = { :name => "Chicken Fried Steak",
              :desc => "A well messages pattie, breaded and fried.",
              :cost => 9.95 }

  attr_reader :product, :price

  def initialize( product = "", price = "" )
    @product = product
    @price = price
  end

  def build
    b = binding
    # create and run templates, filling member data variables
    ERB.new("      <%= PRODUCT[:name] %>
      <%= PRODUCT[:desc] %>
".gsub(/^\s+/, ""), 0, "", "@product").result b
    ERB.new("      <%= PRODUCT[:name] %> -- <%= PRODUCT[:cost] %>
      <%= PRODUCT[:desc] %>
".gsub(/^\s+/, ""), 0, "", "@price").result b
  end
end

# setup template data
listings = Listings.new
listings.build

puts listings.product + "\n" + listings.price

Generates

Chicken Fried Steak
A well messages pattie, breaded and fried.

Chicken Fried Steak -- 9.95
A well messages pattie, breaded and fried.

# File lib/erb.rb, line 795
def initialize(str, safe_level=nil, trim_mode=nil, eoutvar='_erbout')
  @safe_level = safe_level
  compiler = make_compiler(trim_mode)
  set_eoutvar(compiler, eoutvar)
  @src, @enc = *compiler.compile(str)
  @filename = nil
end

Returns revision information for the erb.rb module.

# File lib/erb.rb, line 263
def self.version
  "erb.rb [2.1.0 #{ERB::Revision.split[1]}]"
end

Define unnamed class which has methodname as instance method, and return it.

example:

class MyClass_
  def initialize(arg1, arg2)
    @arg1 = arg1;  @arg2 = arg2
  end
end
filename = 'example.rhtml'  # @arg1 and @arg2 are used in example.rhtml
erb = ERB.new(File.read(filename))
erb.filename = filename
MyClass = erb.def_class(MyClass_, 'render()')
print MyClass.new('foo', 123).render()

# File lib/erb.rb, line 906
def def_class(superklass=Object, methodname='result')
  cls = Class.new(superklass)
  def_method(cls, methodname, @filename || '(ERB)')
  cls
end

Define methodname as instance method of mod from compiled Ruby source.

example:

filename = 'example.rhtml'   # 'arg1' and 'arg2' are used in example.rhtml
erb = ERB.new(File.read(filename))
erb.def_method(MyClass, 'render(arg1, arg2)', filename)
print MyClass.new.render('foo', 123)

# File lib/erb.rb, line 869
def def_method(mod, methodname, fname='(ERB)')
  src = self.src
  magic_comment = "#coding:#{@enc}\n"
  mod.module_eval do
    eval(magic_comment + "def #{methodname}\n" + src + "\nend\n", binding, fname, -2)
  end
end

Create unnamed module, define methodname as instance method of it, and return it.

example:

filename = 'example.rhtml'   # 'arg1' and 'arg2' are used in example.rhtml
erb = ERB.new(File.read(filename))
erb.filename = filename
MyModule = erb.def_module('render(arg1, arg2)')
class MyClass
  include MyModule
end

# File lib/erb.rb, line 887
def def_module(methodname='erb')
  mod = Module.new
  def_method(mod, methodname, @filename || '(ERB)')
  mod
end

Creates a new compiler for ERB. See ERB::Compiler.new for details

# File lib/erb.rb, line 806
def make_compiler(trim_mode)
  ERB::Compiler.new(trim_mode)
end

Executes the generated ERB code to produce a completed template, returning the results of that code. (See ::new for details on how this process can be affected by safe_level.)

b accepts a Binding object which is used to set the context of code evaluation.

# File lib/erb.rb, line 842
def result(b=new_toplevel)
  if @safe_level
    proc {
      $SAFE = @safe_level
      eval(@src, b, (@filename || '(erb)'), 0)
    }.call
  else
    eval(@src, b, (@filename || '(erb)'), 0)
  end
end

Generate results and print them. (see #result)

# File lib/erb.rb, line 830
def run(b=new_toplevel)
  print self.result(b)
end

Can be used to set eoutvar as described in ::new. It's probably easier to just use the constructor though, since calling this method requires the setup of an ERB compiler object.

# File lib/erb.rb, line 822
def set_eoutvar(compiler, eoutvar = '_erbout')
  compiler.put_cmd = "#{eoutvar}.concat"
  compiler.insert_cmd = "#{eoutvar}.concat"
  compiler.pre_cmd = ["#{eoutvar} = ''"]
  compiler.post_cmd = ["#{eoutvar}.force_encoding(__ENCODING__)"]
end

Returns a new binding each time near TOPLEVEL_BINDING for runs that do not specify a binding.

# File lib/erb.rb, line 857
def new_toplevel
  TOPLEVEL_BINDING.dup
end