class Haml::Engine
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
Attributes
The indentation used in the Haml
document, or ‘nil` if the indentation is ambiguous (for example, for a single-level document).
@return [String]
The Haml::Options
instance. See {file:REFERENCE.md#options the Haml
options documentation}.
@return Haml::Options
Public Class Methods
Precompiles the Haml
template.
@param template [String] The Haml
template @param options [{Symbol => Object}] An options hash;
see {file:REFERENCE.md#options the Haml options documentation}
@raise [Haml::Error] if there’s a Haml
syntax error in the template
# File lib/haml/engine.rb, line 54 def initialize(template, options = {}) # Reflect changes of `Haml::Options.defaults` to `Haml::TempleEngine` options, but `#initialize_encoding` # should be run against the arguemnt `options[:encoding]` for backward compatibility with old `Haml::Engine`. options = Options.defaults.dup.tap { |o| o.delete(:encoding) }.merge!(options) @options = Options.new(options) @template = check_haml_encoding(template) do |msg, line| raise Haml::Error.new(msg, line) end @temple_engine = TempleEngine.new(options) @temple_engine.compile(@template) end
Public Instance Methods
Deprecated API for backword compatibility
# File lib/haml/engine.rb, line 69 def compiler @temple_engine end
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 be 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 {Haml::Helpers}, and various instance variables are set (all prefixed with `haml_`).
@param object [Object, Module] The object on which to define the method @param name [String, Symbol] The name of the method to define @param local_names [Array<Symbol>] The names of the locals that can be passed to the proc
# File lib/haml/engine.rb, line 223 def def_method(object, name, *local_names) method = object.is_a?(Module) ? :module_eval : :instance_eval object.send(method, "def #{name}(_haml_locals = {}); #{@temple_engine.precompiled_with_ambles(local_names)}; end", @options.filename, @options.line) end
# File lib/haml/engine.rb, line 44 def options_for_buffer @options.for_buffer end
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`, 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 {Haml::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` 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.
@param scope [Binding, Object] The context in which the template is evaluated @param locals [{Symbol => Object}] Local variables that will be made available
to the template
@param block [#to_proc] A block that can be yielded to within the template @return [String] The rendered template
# File lib/haml/engine.rb, line 113 def render(scope = Object.new, locals = {}, &block) parent = scope.instance_variable_defined?(:@haml_buffer) ? scope.instance_variable_get(:@haml_buffer) : nil buffer = Haml::Buffer.new(parent, @options.for_buffer) if scope.is_a?(Binding) 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.extend(Haml::Helpers) scope_object.instance_variable_set(:@haml_buffer, buffer) begin eval(@temple_engine.precompiled_with_return_value, scope, @options.filename, @options.line) rescue ::SyntaxError => e raise SyntaxError, e.message end ensure # Get rid of the current buffer scope_object.instance_variable_set(:@haml_buffer, buffer.upper) if buffer end
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.
@param scope [Binding, Object] The context in which the template is evaluated @param local_names [Array<Symbol>] The names of the locals that can be passed to the proc @return [Proc] The proc that will run the template
# File lib/haml/engine.rb, line 164 def render_proc(scope = Object.new, *local_names) if scope.is_a?(Binding) scope_object = eval("self", scope) else scope_object = scope scope = scope_object.instance_eval{binding} end begin str = @temple_engine.precompiled_with_ambles(local_names) eval( "Proc.new { |*_haml_locals| _haml_locals = _haml_locals[0] || {}; #{str}}\n", scope, @options.filename, @options.line ) rescue ::SyntaxError => e raise SyntaxError, e.message end end
Private Instance Methods
# File lib/haml/engine.rb, line 232 def set_locals(locals, scope, scope_object) scope_object.instance_variable_set :@_haml_locals, locals set_locals = locals.keys.map { |k| "#{k} = @_haml_locals[#{k.inspect}]" }.join("\n") eval(set_locals, scope) end