class Docile::FallbackContextProxy
@api private
A proxy object with a primary receiver as well as a secondary fallback receiver.
Will attempt to forward all method calls first to the primary receiver, and then to the fallback receiver if the primary does not handle that method.
This is useful for implementing DSL evaluation in the context of an object.
@see Docile.dsl_eval
Constants
- NON_FALLBACK_METHODS
The set of methods which will not fallback from the block’s context to the dsl object.
- NON_PROXIED_INSTANCE_VARIABLES
The set of instance variables which are local to this object and hidden. All other instance variables will be copied in and out of this object from the scope in which this proxy was created.
- NON_PROXIED_METHODS
The set of methods which will not be proxied, but instead answered by this object directly.
Public Class Methods
@param [Object] receiver the primary proxy target to which all methods
initially will be forwarded
@param [Object] fallback the fallback proxy target to which any methods
not handled by `receiver` will be forwarded
# File lib/docile/fallback_context_proxy.rb, line 42 def initialize(receiver, fallback) @__receiver__ = receiver @__fallback__ = fallback # Enables calling DSL methods from helper methods in the block's context unless fallback.respond_to?(:method_missing) # NOTE: There's no {#define_singleton_method} on Ruby 1.8.x singleton_class = (class << fallback; self; end) # instrument {#method_missing} on the block's context to fallback to # the DSL object. This allows helper methods in the block's context to # contain calls to methods on the DSL object. singleton_class. send(:define_method, :method_missing) do |method, *args, &block| m = method.to_sym if !NON_FALLBACK_METHODS.include?(m) && !fallback.respond_to?(m) && receiver.respond_to?(m) receiver.__send__(method.to_sym, *args, &block) else super(method, *args, &block) end end # instrument a helper method to remove the above instrumentation singleton_class. send(:define_method, :__docile_undo_fallback__) do singleton_class.send(:remove_method, :method_missing) singleton_class.send(:remove_method, :__docile_undo_fallback__) end end end
Public Instance Methods
@return [Array<Symbol>] Instance variable names, excluding
{NON_PROXIED_INSTANCE_VARIABLES}
@note on Ruby 1.8.x, the instance variable names are actually of
type `String`.
# File lib/docile/fallback_context_proxy.rb, line 78 def instance_variables # Ruby 1.8.x returns string names, convert to symbols for compatibility super.select { |v| !NON_PROXIED_INSTANCE_VARIABLES.include?(v.to_sym) } end
Proxy all methods, excluding {NON_PROXIED_METHODS}, first to ‘receiver` and then to `fallback` if not found.
# File lib/docile/fallback_context_proxy.rb, line 85 def method_missing(method, *args, &block) if @__receiver__.respond_to?(method.to_sym) @__receiver__.__send__(method.to_sym, *args, &block) else @__fallback__.__send__(method.to_sym, *args, &block) end end