class ERB - Documentation for Ruby 4.1
Description: class ERB: Class **ERB** (the name stands for **Embedded Ruby**) is an easy-to-use, but also very powerful, [template processor][template processor]. a plain-tex
Keywords: ruby,class,ERB

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# class ERB

Class ERB (the name stands for Embedded Ruby) is an easy-to-use, but also very powerful, template processor.

## Usage

Before you can use ERB, you must first require it (examples on this page assume that this has been done):

    require 'erb'

## In Brief

Here’s how ERB works:

- You can create a template: a plain-text string that includes specially formatted tags..

- You can create an ERB object to store the template.

- You can call instance method `ERB#result` to get the result.

ERB supports tags of three kinds:

- Expression tags: each begins with `'<%='`, ends with `'%>'`; contains a Ruby expression; in the result, the value of the expression replaces the entire tag:

      template = 'The magic word is <%= magic_word %>.'
      erb = ERB.new(template)
      magic_word = 'xyzzy'
      erb.result(binding) # => "The magic word is xyzzy."

  The above call to `result` passes argument `binding`, which contains the binding of variable `magic_word` to its string value `'xyzzy'`.

  The below call to `result` need not pass a binding, because its expression `Date::DAYNAMES` is globally defined.

      ERB.new('Today is <%= Date::DAYNAMES[Date.today.wday] %>.').result # => "Today is Monday."

- Execution tags: each begins with `'<%'`, ends with `'%>'`; contains Ruby code to be executed:

       template = '<% File.write("t.txt", "Some stuff.") %>'
       ERB.new(template).result
       File.read('t.txt') # => "Some stuff."

- Comment tags: each begins with `'<%#'`, ends with `'%>'`; contains comment text; in the result, the entire tag is omitted.

       template = 'Some stuff;<%# Note to self: figure out what the stuff is. %> more stuff.'
       ERB.new(template).result # => "Some stuff; more stuff."

## Some Simple Examples

Here’s a simple example of ERB in action:

    template = 'The time is <%= Time.now %>.'
    erb = ERB.new(template)
    erb.result
    # => "The time is 2025-09-09 10:49:26 -0500."

Details:

1. A plain-text string is assigned to variable `template`. Its embedded expression tag `'<%= Time.now %>'` includes a Ruby expression, `Time.now`.

2. The string is put into a new ERB object, and stored in variable `erb`.

3. Method call `erb.result` generates a string that contains the run-time value of `Time.now`, as computed at the time of the call.

The ERB object may be re-used:

    erb.result
    # => "The time is 2025-09-09 10:49:33 -0500."

Another example:

    template = 'The magic word is <%= magic_word %>.'
    erb = ERB.new(template)
    magic_word = 'abracadabra'
    erb.result(binding)
    # => "The magic word is abracadabra."

Details:

1. As before, a plain-text string is assigned to variable `template`. Its embedded expression tag `'<%= magic_word %>'` has a variable name, `magic_word`.

2. The string is put into a new ERB object, and stored in variable `erb`; note that `magic_word` need not be defined before the ERB object is created.

3. `magic_word = 'abracadabra'` assigns a value to variable `magic_word`.

4. Method call `erb.result(binding)` generates a string that contains the value of `magic_word`.

As before, the ERB object may be re-used:

    magic_word = 'xyzzy'
    erb.result(binding)
    # => "The magic word is xyzzy."

## Bindings

A call to method `result`, which produces the formatted result string, requires a Binding object as its argument.

The binding object provides the bindings for expressions in expression tags.

There are three ways to provide the required binding:

- Default binding.

- Local binding.

- Augmented binding

### Default `Binding`

When you pass no `binding` argument to method `result`, the method uses its default binding: the one returned by method `new_toplevel`. This binding has the bindings defined by Ruby itself, which are those for Ruby’s constants and variables.

That binding is sufficient for an expression tag that refers only to Ruby’s constants and variables; these expression tags refer only to Ruby’s global constant `RUBY_COPYRIGHT` and global variable `$0`:

    template = <<TEMPLATE
    The Ruby copyright is <%= RUBY_COPYRIGHT.inspect %>.
    The current process is <%= $0 %>.
    TEMPLATE
    puts ERB.new(template).result
    The Ruby copyright is "ruby - Copyright (C) 1993-2025 Yukihiro Matsumoto".
    The current process is irb.

(The current process is `irb` because that’s where we’re doing these examples!)

### Local `Binding`

The default binding is not sufficient for an expression that refers to a a constant or variable that is not defined there:

    Foo = 1 # Defines local constant Foo.
    foo = 2 # Defines local variable foo.
    template = <<TEMPLATE
    The current value of constant Foo is <%= Foo %>.
    The current value of variable foo is <%= foo %>.
    The Ruby copyright is <%= RUBY_COPYRIGHT.inspect %>.
    The current process is <%= $0 %>.
    TEMPLATE
    erb = ERB.new(template)

This call below raises `NameError` because although `Foo` and `foo` are defined locally, they are not defined in the default binding:

    erb.result # Raises NameError.

To make the locally-defined constants and variables available, you can call `result` with the local binding:

    puts erb.result(binding)
    The current value of constant Foo is 1.
    The current value of variable foo is 2.
    The Ruby copyright is "ruby - Copyright (C) 1993-2025 Yukihiro Matsumoto".
    The current process is irb.

### Augmented `Binding`

Another way to make variable bindings (but not constant bindings) available is to use method `result_with_hash(hash)`; the passed hash has name/value pairs that are to be used to define and assign variables in a copy of the default binding:

    template = <<TEMPLATE
    The current value of variable bar is <%= bar %>.
    The current value of variable baz is <%= baz %>.
    The Ruby copyright is <%= RUBY_COPYRIGHT.inspect %>.
    The current process is <%= $0 %>.
    TEMPLATE
    erb = ERB.new(template)

Both of these calls raise `NameError`, because `bar` and `baz` are not defined in either the default binding or the local binding.

    puts erb.result          # Raises NameError.
    puts erb.result(binding) # Raises NameError.

This call passes a hash that causes `bar` and `baz` to be defined in a new binding (derived from `new_toplevel`):

    hash = {bar: 3, baz: 4}
    puts erb.result_with_hash(hash)
    The current value of variable bar is 3.
    The current value of variable baz is 4.
    The Ruby copyright is "ruby - Copyright (C) 1993-2025 Yukihiro Matsumoto".
    The current process is irb.

## Tags

The examples above use expression tags. These are the tags available in ERB:

- Expression tag: the tag contains a Ruby expression; in the result, the entire tag is to be replaced with the run-time value of the expression.

- Execution tag: the tag contains Ruby code; in the result, the entire tag is to be replaced with the run-time value of the code.

- Comment tag: the tag contains comment code; in the result, the entire tag is to be omitted.

### Expression Tags

You can embed a Ruby expression in a template using an expression tag.

Its syntax is `<%= _expression_ %>`, where expression is any valid Ruby expression.

When you call method `result`, the method evaluates the expression and replaces the entire expression tag with the expression’s value:

    ERB.new('Today is <%= Date::DAYNAMES[Date.today.wday] %>.').result
    # => "Today is Monday."
    ERB.new('Tomorrow will be <%= Date::DAYNAMES[Date.today.wday + 1] %>.').result
    # => "Tomorrow will be Tuesday."
    ERB.new('Yesterday was <%= Date::DAYNAMES[Date.today.wday - 1] %>.').result
    # => "Yesterday was Sunday."

Note that whitespace before and after the expression is allowed but not required, and that such whitespace is stripped from the result.

    ERB.new('My appointment is on <%=Date::DAYNAMES[Date.today.wday + 2]%>.').result
    # => "My appointment is on Wednesday."
    ERB.new('My appointment is on <%=     Date::DAYNAMES[Date.today.wday + 2]    %>.').result
    # => "My appointment is on Wednesday."

### Execution Tags

You can embed Ruby executable code in template using an execution tag.

Its syntax is `<% _code_ %>`, where code is any valid Ruby code.

When you call method `result`, the method executes the code and removes the entire execution tag (generating no text in the result):

    ERB.new('foo <% Dir.chdir("C:/") %> bar').result # => "foo  bar"

Whitespace before and after the embedded code is optional:

    ERB.new('foo <%Dir.chdir("C:/")%> bar').result   # => "foo  bar"

You can interleave text with execution tags to form a control structure such as a conditional, a loop, or a `case` statements.

Conditional:

    template = <<TEMPLATE
    <% if verbosity %>
    An error has occurred.
    <% else %>
    Oops!
    <% end %>
    TEMPLATE
    erb = ERB.new(template)
    verbosity = true
    erb.result(binding)
    # => "\nAn error has occurred.\n\n"
    verbosity = false
    erb.result(binding)
    # => "\nOops!\n\n"

Note that the interleaved text may itself contain expression tags:

Loop:

    template = <<TEMPLATE
    <% Date::ABBR_DAYNAMES.each do |dayname| %>
    <%= dayname %>
    <% end %>
    TEMPLATE
    ERB.new(template).result
    # => "\nSun\n\nMon\n\nTue\n\nWed\n\nThu\n\nFri\n\nSat\n\n"

Other, non-control, lines of Ruby code may be interleaved with the text, and the Ruby code may itself contain regular Ruby comments:

    template = <<TEMPLATE
    <% 3.times do %>
    <%= Time.now %>
    <% sleep(1) # Let's make the times different. %>
    <% end %>
    TEMPLATE
    ERB.new(template).result
    # => "\n2025-09-09 11:36:02 -0500\n\n\n2025-09-09 11:36:03 -0500\n\n\n2025-09-09 11:36:04 -0500\n\n\n"

The execution tag may also contain multiple lines of code:

    template = <<TEMPLATE
    <%
      (0..2).each do |i|
        (0..2).each do |j|
    %>
    * <%=i%>,<%=j%>
    <%
        end
      end
    %>
    TEMPLATE
    ERB.new(template).result
    # => "\n* 0,0\n\n* 0,1\n\n* 0,2\n\n* 1,0\n\n* 1,1\n\n* 1,2\n\n* 2,0\n\n* 2,1\n\n* 2,2\n\n"

#### Shorthand Format for Execution Tags

You can use keyword argument `trim_mode: '%'` to enable a shorthand format for execution tags; this example uses the shorthand format `% _code_` instead of `<% _code_ %>`:

    template = <<TEMPLATE
    % priorities.each do |priority|
      * <%= priority %>
    % end
    TEMPLATE
    erb = ERB.new(template, trim_mode: '%')
    priorities = [ 'Run Ruby Quiz',
                   'Document Modules',
                   'Answer Questions on Ruby Talk' ]
    puts erb.result(binding)
      * Run Ruby Quiz
      * Document Modules
      * Answer Questions on Ruby Talk

Note that in the shorthand format, the character `'%'` must be the first character in the code line (no leading whitespace).

#### Suppressing Unwanted Blank Lines

With keyword argument `trim_mode` not given, all blank lines go into the result:

    template = <<TEMPLATE
    <% if true %>
    <%= RUBY_VERSION %>
    <% end %>
    TEMPLATE
    ERB.new(template).result.lines.each {|line| puts line.inspect }
    "\n"
    "3.4.5\n"
    "\n"

You can give `trim_mode: '-'`, you can suppress each blank line whose source line ends with `-%>` (instead of `%>`):

    template = <<TEMPLATE
    <% if true -%>
    <%= RUBY_VERSION %>
    <% end -%>
    TEMPLATE
    ERB.new(template, trim_mode: '-').result.lines.each {|line| puts line.inspect }
    "3.4.5\n"

It is an error to use the trailing `'-%>'` notation without `trim_mode: '-'`:

    ERB.new(template).result.lines.each {|line| puts line.inspect } # Raises SyntaxError.

#### Suppressing Unwanted Newlines

Consider this template:

    template = <<TEMPLATE
    <% RUBY_VERSION %>
    <%= RUBY_VERSION %>
    foo <% RUBY_VERSION %>
    foo <%= RUBY_VERSION %>
    TEMPLATE

With keyword argument `trim_mode` not given, all newlines go into the result:

    ERB.new(template).result.lines.each {|line| puts line.inspect }
    "\n"
    "3.4.5\n"
    "foo \n"
    "foo 3.4.5\n"

You can give `trim_mode: '>'` to suppress the trailing newline for each line that ends with `'%>'` (regardless of its beginning):

    ERB.new(template, trim_mode: '>').result.lines.each {|line| puts line.inspect }
    "3.4.5foo foo 3.4.5"

You can give `trim_mode: '<>'` to suppress the trailing newline for each line that both begins with `'<%'` and ends with `'%>'`:

    ERB.new(template, trim_mode: '<>').result.lines.each {|line| puts line.inspect }
    "3.4.5foo \n"
    "foo 3.4.5\n"

#### Combining Trim Modes

You can combine certain trim modes:

- `'%-'`: Enable shorthand and omit each blank line ending with `'-%>'`.

- `'%>'`: Enable shorthand and omit newline for each line ending with `'%>'`.

- `'%<>'`: Enable shorthand and omit newline for each line starting with `'<%'` and ending with `'%>'`.

### Comment Tags

You can embed a comment in a template using a comment tag; its syntax is `<%# _text_ %>`, where text is the text of the comment.

When you call method `result`, it removes the entire comment tag (generating no text in the result).

Example:

    template = 'Some stuff;<%# Note to self: figure out what the stuff is. %> more stuff.'
    ERB.new(template).result # => "Some stuff; more stuff."

A comment tag may appear anywhere in the template.

Note that the beginning of the tag must be `'<%#'`, not `'<% #'`.

In this example, the tag begins with `'<% #'`, and so is an execution tag, not a comment tag; the cited code consists entirely of a Ruby-style comment (which is of course ignored):

    ERB.new('Some stuff;<% # Note to self: figure out what the stuff is. %> more stuff.').result
    # => "Some stuff;"

## Encodings

An ERB object has an encoding, which is by default the encoding of the template string; the result string will also have that encoding.

    template = <<TEMPLATE
    <%# Comment. %>
    TEMPLATE
    erb = ERB.new(template)
    template.encoding   # => #<Encoding:UTF-8>
    erb.encoding        # => #<Encoding:UTF-8>
    erb.result.encoding # => #<Encoding:UTF-8>

You can specify a different encoding by adding a magic comment at the top of the given template:

    template = <<TEMPLATE
    <%#-*- coding: Big5 -*-%>
    <%# Comment. %>
    TEMPLATE
    erb = ERB.new(template)
    template.encoding   # => #<Encoding:UTF-8>
    erb.encoding        # => #<Encoding:Big5>
    erb.result.encoding # => #<Encoding:Big5>

## Error Reporting

Consider this template (containing an error):

    template = '<%= nosuch %>'
    erb = ERB.new(template)

When ERB reports an error, it includes a file name (if available) and a line number; the file name comes from method `filename`, the line number from method `lineno`.

Initially, those values are `nil` and `0`, respectively; these initial values are reported as `'(erb)'` and `1`, respectively:

    erb.filename # => nil
    erb.lineno   # => 0
    erb.result
    (erb):1:in '<main>': undefined local variable or method 'nosuch' for main (NameError)

You can use methods `filename=` and `lineno=` to assign values that are more meaningful in your context:

    erb.filename = 't.txt'
    erb.lineno = 555
    erb.result
    t.txt:556:in '<main>': undefined local variable or method 'nosuch' for main (NameError)

You can use method `location=` to set both values:

    erb.location = ['u.txt', 999]
    erb.result
    u.txt:1000:in '<main>': undefined local variable or method 'nosuch' for main (NameError)

## Plain Text with Embedded Ruby

Here’s a plain-text template; it uses the literal notation `'%q{ ... }'` to define the template (see %q literals); this avoids problems with backslashes.

    template = %q{
    From:  James Edward Gray II <james@grayproductions.net>
    To:  <%= to %>
    Subject:  Addressing Needs

    <%= to[/\w+/] %>:

    Just wanted to send a quick note assuring that your needs are being
    addressed.

    I want you to know that my team will keep working on the issues,
    especially:

    <%# ignore numerous minor requests -- focus on priorities %>
    % priorities.each do |priority|
      * <%= priority %>
    % end

    Thanks for your patience.

    James Edward Gray II
    }

The template will need these:

    to = 'Community Spokesman <spokesman@ruby_community.org>'
    priorities = [ 'Run Ruby Quiz',
                   'Document Modules',
                   'Answer Questions on Ruby Talk' ]

Finally, create the ERB object and get the result

    erb = ERB.new(template, trim_mode: '%<>')
    puts erb.result(binding)

    From:  James Edward Gray II <james@grayproductions.net>
    To:  Community Spokesman <spokesman@ruby_community.org>
    Subject:  Addressing Needs

    Community:

    Just wanted to send a quick note assuring that your needs are being
    addressed.

    I want you to know that my team will keep working on the issues,
    especially:

    * Run Ruby Quiz
    * Document Modules
    * Answer Questions on Ruby Talk

    Thanks for your patience.

    James Edward Gray II

## HTML with Embedded Ruby

This example shows an HTML template.

First, here’s a custom class, `Product`:

    class Product
      def initialize(code, name, desc, cost)
        @code = code
        @name = name
        @desc = desc
        @cost = cost
        @features = []
      end

      def add_feature(feature)
        @features << feature
      end

      # Support templating of member data.
      def get_binding
        binding
      end

    end

The template below will need these values:

    toy = Product.new('TZ-1002',
                      'Rubysapien',
                      "Geek's Best Friend!  Responds to Ruby commands...",
                      999.95
                      )
    toy.add_feature('Listens for verbal commands in the Ruby language!')
    toy.add_feature('Ignores Perl, Java, and all C variants.')
    toy.add_feature('Karate-Chop Action!!!')
    toy.add_feature('Matz signature on left leg.')
    toy.add_feature('Gem studded eyes... Rubies, of course!')

Here’s the HTML:

    template = <<TEMPLATE
    <html>
      <head><title>Ruby Toys -- <%= @name %></title></head>
      <body>
        <h1><%= @name %> (<%= @code %>)</h1>
        <p><%= @desc %></p>
        <ul>
          <% @features.each do |f| %>
            <li><b><%= f %></b></li>
          <% end %>
        </ul>
        <p>
          <% if @cost < 10 %>
            <b>Only <%= @cost %>!!!</b>
          <% else %>
             Call for a price, today!
          <% end %>
        </p>
      </body>
    </html>
    TEMPLATE

Finally, create the ERB object and get the result (omitting some blank lines):

    erb = ERB.new(template)
    puts erb.result(toy.get_binding)
    <html>
      <head><title>Ruby Toys -- Rubysapien</title></head>
      <body>
        <h1>Rubysapien (TZ-1002)</h1>
        <p>Geek's Best Friend!  Responds to Ruby commands...</p>
        <ul>
            <li><b>Listens for verbal commands in the Ruby language!</b></li>
            <li><b>Ignores Perl, Java, and all C variants.</b></li>
            <li><b>Karate-Chop Action!!!</b></li>
            <li><b>Matz signature on left leg.</b></li>
            <li><b>Gem studded eyes... Rubies, of course!</b></li>
        </ul>
        <p>
             Call for a price, today!
        </p>
      </body>
    </html>

## Other Template Processors

Various Ruby projects have their own template processors. The Ruby Processing System RDoc, for example, has one that can be used elsewhere.

Other popular template processors may found in the Template Engines page of the Ruby Toolbox.

### Constants

VERSION

  The string ERB version.

### Attributes

encoding [R]

Returns the encoding of `self`; see Encodings:

filename [RW]

Sets or returns the file name to be used in reporting errors; see Error Reporting.

lineno [RW]

Sets or returns the line number to be used in reporting errors; see Error Reporting.

src [R]

Returns the Ruby code that, when executed, generates the result; the code is executed by method `result`, and by its wrapper methods `result_with_hash` and `run`:

    template = 'The time is <%= Time.now %>.'
    erb = ERB.new(template)
    erb.src
    # => "#coding:UTF-8\n_erbout = +''; _erbout.<< \"The time is \".freeze; _erbout.<<(( Time.now ).to_s); _erbout.<< \".\".freeze; _erbout"
    erb.result
    # => "The time is 2025-09-18 15:58:08 -0500."

In a more readable format:

      # puts erb.src.split('; ')
      # #coding:UTF-8
      # _erbout = +''
      # _erbout.<< "The time is ".freeze
      # _erbout.<<(( Time.now ).to_s)
      # _erbout.<< ".".freeze
      # _erbout

Variable `_erbout` is used to store the intermediate results in the code; the name `_erbout` is the default in `ERB.new`, and can be changed via keyword argument `eoutvar`:

    erb = ERB.new(template, eoutvar: '_foo')
    puts template.src.split('; ')
    #coding:UTF-8
    _foo = +''
    _foo.<< "The time is ".freeze
    _foo.<<(( Time.now ).to_s)
    _foo.<< ".".freeze
    _foo

### Public Class Methods

new(template, trim_mode: nil, eoutvar: '_erbout')
Source

    # File lib/erb.rb, line 831
    def initialize(str, trim_mode: nil, eoutvar: '_erbout')
      compiler = make_compiler(trim_mode)
      set_eoutvar(compiler, eoutvar)
      @src, @encoding, @frozen_string = *compiler.compile(str)
      @src.freeze
      @filename = nil
      @lineno = 0
      @_init = self.class.singleton_class
    end

Returns a new ERB object containing the given string +template+.

For details about `template`, its embedded tags, and generated results, see `ERB`.

Keyword Argument `trim_mode`

You can use keyword argument `trim_mode: '%'` to enable the shorthand format for execution tags.

This value allows blank line control:

- `'-'`: Omit each blank line ending with `'%>'`.

Other values allow newline control:

- `'>'`: Omit newline for each line ending with `'%>'`.

- `'<>'`: Omit newline for each line starting with `'<%'` and ending with `'%>'`.

You can also combine trim modes.

Keyword Argument `eoutvar`

The string value of keyword argument `eoutvar` specifies the name of the variable that method `result` uses to construct its result string; see `src`.

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.

It’s good practice to choose a variable name that begins with an underscore: `'_'`.

version → string
Source

    # File lib/erb.rb, line 786
    def self.version
      VERSION
    end

Returns the string ERB version.

### Public Instance Methods

def_class(super_class = Object, method_name = 'result') → new_class
Source

    # File lib/erb.rb, line 1173
    def def_class(superklass=Object, methodname='result')
      cls = Class.new(superklass)
      def_method(cls, methodname, @filename || '(ERB)')
      cls
    end

Returns a new nameless class whose superclass is `super_class`, and which has instance method `method_name`.

Create a template from HTML that has embedded expression tags that use `@arg1` and `@arg2`:

    html = <<TEMPLATE
    <html>
    <body>
      <p><%= @arg1 %></p>
      <p><%= @arg2 %></p>
    </body>
    </html>
    TEMPLATE
    template = ERB.new(html)

Create a base class that has `@arg1` and `@arg2`:

    class MyBaseClass
      def initialize(arg1, arg2)
        @arg1 = arg1
        @arg2 = arg2
      end
    end

Use method `def_class` to create a subclass that has method `:render`:

    MySubClass = template.def_class(MyBaseClass, :render)

Generate the result:

    puts MySubClass.new('foo', 123).render
    <html>
    <body>
      <p>foo</p>
      <p>123</p>
    </body>
    </html>

def_method(module, method_signature, filename = '(ERB)') → method_name
Source

    # File lib/erb.rb, line 1088
    def def_method(mod, methodname, fname='(ERB)')
      unless @_init.equal?(self.class.singleton_class)
        raise ArgumentError, "not initialized"
      end
      src = self.src.sub(/^(?!#|$)/) {"def #{methodname}\n"} << "\nend\n"
      mod.module_eval do
        eval(src, binding, fname, -1)
      end
    end

Creates and returns a new instance method in the given module `module`; returns the method name as a symbol.

The method is created from the given `method_signature`, which consists of the method name and its argument names (if any).

The `filename` sets the value of `filename`; see Error Reporting.

    template = '<%= arg1 %> <%= arg2 %>'
    erb = ERB.new(template)
    MyModule = Module.new
    erb.def_method(MyModule, 'render(arg1, arg2)') # => :render
    class MyClass; include MyModule; end
    MyClass.new.render('foo', 123)                      # => "foo 123"

def_module(method_name = 'erb') → new_module
Source

    # File lib/erb.rb, line 1116
    def def_module(methodname='erb')
      mod = Module.new
      def_method(mod, methodname, @filename || '(ERB)')
      mod
    end

Returns a new nameless module that has instance method `method_name`.

    template = '<%= arg1 %> <%= arg2 %>'
    erb = ERB.new(template)
    MyModule = template.def_module('render(arg1, arg2)')
    class MyClass
      include MyModule
    end
    MyClass.new.render('foo', 123)
    # => "foo 123"

location = [filename, lineno] → [filename, lineno]
location = filename → filename
Source

    # File lib/erb.rb, line 937
    def location=((filename, lineno))
      @filename = filename
      @lineno = lineno if lineno
    end

Sets the values of `filename` and, if given, `lineno`; see Error Reporting.

make_compiler → erb_compiler
Source

    # File lib/erb.rb, line 854
    def make_compiler(trim_mode)
      ERB::Compiler.new(trim_mode)
    end

Returns a new ERB::Compiler with the given `trim_mode`; for `trim_mode` values, see `ERB.new`:

    ERB.new('').make_compiler(nil)
    # => #<ERB::Compiler:0x000001cff9467678 @insert_cmd="print", @percent=false, @post_cmd=[], @pre_cmd=[], @put_cmd="print", @trim_mode=nil>

result(binding = new_toplevel) → new_string
Source

    # File lib/erb.rb, line 1008
    def result(b=new_toplevel)
      unless @_init.equal?(self.class.singleton_class)
        raise ArgumentError, "not initialized"
      end
      eval(@src, b, (@filename || '(erb)'), @lineno)
    end

Returns the string result formed by processing ERB tags found in the stored template in `self`.

With no argument given, uses the default binding; see Default Binding.

With argument `binding` given, uses the local binding; see Local Binding.

See also `result_with_hash`.

result_with_hash(hash) → new_string
Source

    # File lib/erb.rb, line 1027
    def result_with_hash(hash)
      b = new_toplevel(hash.keys)
      hash.each_pair do |key, value|
        b.local_variable_set(key, value)
      end
      result(b)
    end

Returns the string result formed by processing ERB tags found in the stored string in `self`; see Augmented Binding.

See also `result`.

run(binding = new_toplevel) → nil
Source

    # File lib/erb.rb, line 986
    def run(b=new_toplevel)
      print self.result(b)
    end

Like `result`, but prints the result string (instead of returning it); returns `nil`.

set_eoutvar(compiler, eoutvar = '_erbout') → [eoutvar]
Source

    # File lib/erb.rb, line 972
    def set_eoutvar(compiler, eoutvar = '_erbout')
      compiler.put_cmd = "#{eoutvar}.<<"
      compiler.insert_cmd = "#{eoutvar}.<<"
      compiler.pre_cmd = ["#{eoutvar} = +''"]
      compiler.post_cmd = [eoutvar]
    end

Sets the `eoutvar` value in the ERB::Compiler object `compiler`; returns a 1-element array containing the value of `eoutvar`:

    template = ERB.new('')
    compiler = template.make_compiler(nil)
    pp compiler
    #<ERB::Compiler:0x000001cff8a9aa00
     @insert_cmd="print",
     @percent=false,
     @post_cmd=[],
     @pre_cmd=[],
     @put_cmd="print",
     @trim_mode=nil>
    template.set_eoutvar(compiler, '_foo') # => ["_foo"]
    pp compiler
    #<ERB::Compiler:0x000001cff8a9aa00
     @insert_cmd="_foo.<<",
     @percent=false,
     @post_cmd=["_foo"],
     @pre_cmd=["_foo = +''"],
     @put_cmd="_foo.<<",
     @trim_mode=nil>

### Private Instance Methods

new_toplevel(symbols) → new_binding
Source

    # File lib/erb.rb, line 1051
    def new_toplevel(vars = nil)
      b = TOPLEVEL_BINDING
      if vars
        vars = vars.select {|v| b.local_variable_defined?(v)}
        unless vars.empty?
          return b.eval("tap {|;#{vars.join(',')}| break binding}")
        end
      end
      b.dup
    end

Returns a new binding based on `TOPLEVEL_BINDING`; used to create a default binding for a call to `result`.

See Default Binding.

Argument `symbols` is an array of symbols; each symbol `symbol` is defined as a new variable to hide and prevent it from overwriting a variable of the same name already defined within the binding.