Class: Haml::Engine

Inherits:
Object
  • Object
show all
Includes:
Precompiler
Defined in:
lib/haml/engine.rb

Overview

This is the frontend for using Haml programmatically. It can be directly used by the user by creating a new instance and calling #render to render the template. For example:

template = File.read('templates/really_cool_template.haml')
haml_engine = Haml::Engine.new(template)
output = haml_engine.render
puts output

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Precompiler

#push_silent_with_haml_block_deprecation

Constructor Details

#initialize(template, options = {}) ⇒ Engine

Precompiles the Haml template.

Parameters:

Raises:

  • (Haml::Error) —

    if there's a Haml syntax error in the template



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# File 'lib/haml/engine.rb', line 72

def initialize(template, options = {})
  @options = {
    :suppress_eval => false,
    :attr_wrapper => "'",

    # Don't forget to update the docs in doc-src/HAML_REFERENCE.md
    # if you update these
    :autoclose => %w[meta img link br hr input area param col base],
    :preserve => %w[textarea pre code],

    :filename => '(haml)',
    :line => 1,
    :ugly => false,
    :format => :xhtml,
    :escape_html => false,
  }


  template = check_haml_encoding(template) do |msg, line|
    raise Haml::Error.new(msg, line)
  end

  unless ruby1_8?
    @options[:encoding] = Encoding.default_internal || template.encoding
    @options[:encoding] = "utf-8" if @options[:encoding].name == "US-ASCII"
  end
  @options.merge! options.reject {|k, v| v.nil?}
  @index = 0

  unless [:xhtml, :html4, :html5].include?(@options[:format])
    raise Haml::Error, "Invalid output format #{@options[:format].inspect}"
  end

  if @options[:encoding] && @options[:encoding].is_a?(Encoding)
    @options[:encoding] = @options[:encoding].name
  end

  # :eod is a special end-of-document marker
  @template = (template.rstrip).split(/\r\n|\r|\n/) + [:eod, :eod]
  @template_index = 0
  @to_close_stack = []
  @output_tabs = 0
  @template_tabs = 0
  @flat = false
  @newlines = 0
  @precompiled = ''
  @to_merge = []
  @tab_change  = 0

  precompile
rescue Haml::Error => e
  if @index || e.line
    e.backtrace.unshift "#{@options[:filename]}:#{(e.line ? e.line + 1 : @index) + @options[:line] - 1}"
  end
  raise
end

Instance Attribute Details

#indentation ⇒ String

The indentation used in the Haml document, or nil if the indentation is ambiguous (for example, for a single-level document).

Returns:

  • (String) 


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# File 'lib/haml/engine.rb', line 31

def indentation
  @indentation
end

#options ⇒ {Symbol => Object}

The options hash. See the Haml options documentation.

Returns:

  • ({Symbol => Object}) 


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# File 'lib/haml/engine.rb', line 24

def options
  @options
end

Instance Method Details

#def_method(object, name, *local_names)

Defines a method on object with the given name that renders the template and returns the result as a string.

If object is a class or module, the method will instead by defined as an instance method. For example:

t = Time.now
Haml::Engine.new("%p\n  Today's date is\n  .date= self.to_s").def_method(t, :render)
t.render #=> "<p>\n  Today's date is\n  <div class='date'>Fri Nov 23 18:28:29 -0800 2007</div>\n</p>\n"

Haml::Engine.new(".upcased= upcase").def_method(String, :upcased_div)
"foobar".upcased_div #=> "<div class='upcased'>FOOBAR</div>\n"

The first argument of the defined method is a hash of local variable names to values. However, due to an unfortunate Ruby quirk, the local variables which can be assigned must be pre-declared. This is done with the local_names argument. For example:

# This works
obj = Object.new
Haml::Engine.new("%p= foo").def_method(obj, :render, :foo)
obj.render(:foo => "Hello!") #=> "<p>Hello!</p>"

# This doesn't
obj = Object.new
Haml::Engine.new("%p= foo").def_method(obj, :render)
obj.render(:foo => "Hello!") #=> NameError: undefined local variable or method `foo'

Note that Haml modifies the evaluation context (either the scope object or the self object of the scope binding). It extends Helpers, and various instance variables are set (all prefixed with haml_).

Parameters:

  • object (Object, Module) —

    The object on which to define the method

  • name (String, Symbol) —

    The name of the method to define

  • local_names (Array<Symbol>) —

    The names of the locals that can be passed to the proc



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# File 'lib/haml/engine.rb', line 272

def def_method(object, name, *local_names)
  method = object.is_a?(Module) ? :module_eval : :instance_eval

  object.send(method, "def #{name}(_haml_locals = {}); #{precompiled_with_ambles(local_names)}; end",
              @options[:filename], @options[:line])
end

#html4? ⇒ Boolean

Returns Whether or not the format is HTML4.

Returns:

  • (Boolean) —

    Whether or not the format is HTML4.



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# File 'lib/haml/engine.rb', line 44

def html4?
  @options[:format] == :html4
end

#html5? ⇒ Boolean

Returns Whether or not the format is HTML5.

Returns:

  • (Boolean) —

    Whether or not the format is HTML5.



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# File 'lib/haml/engine.rb', line 49

def html5?
  @options[:format] == :html5
end

#html? ⇒ Boolean

Returns Whether or not the format is any flavor of HTML.

Returns:

  • (Boolean) —

    Whether or not the format is any flavor of HTML.



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# File 'lib/haml/engine.rb', line 39

def html?
  html4? or html5?
end

#options_for_buffer ⇒ {Symbol => Object} (protected)

Returns a subset of #options: those that Buffer cares about. All of the values here are such that when #inspect is called on the hash, it can be Kernel#evaled to get the same result back.

See the Haml options documentation.

Returns:

  • ({Symbol => Object}) —

    The options hash



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# File 'lib/haml/engine.rb', line 288

def options_for_buffer
  {
    :autoclose => @options[:autoclose],
    :preserve => @options[:preserve],
    :attr_wrapper => @options[:attr_wrapper],
    :ugly => @options[:ugly],
    :format => @options[:format],
    :encoding => @options[:encoding],
    :escape_html => @options[:escape_html],
  }
end

#precompiled ⇒ String

The source code that is evaluated to produce the Haml document.

In Ruby 1.9, this is automatically converted to the correct encoding (see the :encoding option).

Returns:

  • (String) 


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# File 'lib/haml/engine.rb', line 59

def precompiled
  return @precompiled if ruby1_8?
  encoding = Encoding.find(@options[:encoding])
  return @precompiled.force_encoding(encoding) if encoding == Encoding::BINARY
  return @precompiled.encode(encoding)
end

#render(scope = Object.new, locals = {}, &block) ⇒ String Also known as: to_html

Processes the template and returns the result as a string.

scope is the context in which the template is evaluated. If it's a Binding or Proc object, Haml uses it as the second argument to Kernel#eval; otherwise, Haml just uses its #instance_eval context.

Note that Haml modifies the evaluation context (either the scope object or the self object of the scope binding). It extends Helpers, and various instance variables are set (all prefixed with haml_). For example:

s = "foobar"
Haml::Engine.new("%p= upcase").render(s) #=> "<p>FOOBAR</p>"

# s now extends Haml::Helpers
s.respond_to?(:html_attrs) #=> true

locals is a hash of local variables to make available to the template. For example:

Haml::Engine.new("%p= foo").render(Object.new, :foo => "Hello, world!") #=> "<p>Hello, world!</p>"

If a block is passed to render, that block is run when yield is called within the template.

Due to some Ruby quirks, if scope is a Binding or Proc object and a block is given, the evaluation context may not be quite what the user expects. In particular, it's equivalent to passing eval("self", scope) as scope. This won't have an effect in most cases, but if you're relying on local variables defined in the context of scope, they won't work.

Parameters:

  • scope (Binding, Proc, Object) (defaults to: Object.new) —

    The context in which the template is evaluated

  • locals ({Symbol => Object}) (defaults to: {}) —

    Local variables that will be made available to the template

  • block (#to_proc) —

    A block that can be yielded to within the template

Returns:

  • (String) —

    The rendered template



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# File 'lib/haml/engine.rb', line 170

def render(scope = Object.new, locals = {}, &block)
  buffer = Haml::Buffer.new(scope.instance_variable_get('@haml_buffer'), options_for_buffer)

  if scope.is_a?(Binding) || scope.is_a?(Proc)
    scope_object = eval("self", scope)
    scope = scope_object.instance_eval{binding} if block_given?
  else
    scope_object = scope
    scope = scope_object.instance_eval{binding}
  end

  set_locals(locals.merge(:_hamlout => buffer, :_erbout => buffer.buffer), scope, scope_object)

  scope_object.instance_eval do
    extend Haml::Helpers
    @haml_buffer = buffer
  end

  eval(precompiled + ";" + precompiled_method_return_value,
    scope, @options[:filename], @options[:line])
ensure
  # Get rid of the current buffer
  scope_object.instance_eval do
    @haml_buffer = buffer.upper
  end
end

#render_proc(scope = Object.new, *local_names) ⇒ Proc

Returns a proc that, when called, renders the template and returns the result as a string.

scope works the same as it does for render.

The first argument of the returned proc is a hash of local variable names to values. However, due to an unfortunate Ruby quirk, the local variables which can be assigned must be pre-declared. This is done with the local_names argument. For example:

# This works
Haml::Engine.new("%p= foo").render_proc(Object.new, :foo).call :foo => "Hello!"
  #=> "<p>Hello!</p>"

# This doesn't
Haml::Engine.new("%p= foo").render_proc.call :foo => "Hello!"
  #=> NameError: undefined local variable or method `foo'

The proc doesn't take a block; any yields in the template will fail.

Parameters:

  • scope (Binding, Proc, Object) (defaults to: Object.new) —

    The context in which the template is evaluated

  • local_names (Array<Symbol>) —

    The names of the locals that can be passed to the proc

Returns:

  • (Proc) —

    The proc that will run the template



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# File 'lib/haml/engine.rb', line 222

def render_proc(scope = Object.new, *local_names)
  if scope.is_a?(Binding) || scope.is_a?(Proc)
    scope_object = eval("self", scope)
  else
    scope_object = scope
    scope = scope_object.instance_eval{binding}
  end

  eval("Proc.new { |*_haml_locals| _haml_locals = _haml_locals[0] || {};" +
       precompiled_with_ambles(local_names) + "}\n", scope, @options[:filename], @options[:line])
end

#xhtml? ⇒ Boolean

Returns Whether or not the format is XHTML.

Returns:

  • (Boolean) —

    Whether or not the format is XHTML.



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# File 'lib/haml/engine.rb', line 34

def xhtml?
  not html?
end