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# Copyright 2004, 2006 by Jim Weirich (jim@weirichhouse.org).
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# Permission is granted for use, copying, modification, distribution,
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# and distribution of modified versions of this work as long as the
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# above copyright notice is included.
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######################################################################
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# BlankSlate provides an abstract base class with no predefined
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# methods (except for <tt>\_\_send__</tt> and <tt>\_\_id__</tt>).
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# BlankSlate is useful as a base class when writing classes that
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# depend upon <tt>method_missing</tt> (e.g. dynamic proxies).
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# Hide the method named +name+ in the BlankSlate class. Don't
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# hide +instance_eval+ or any method beginning with "__".
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if instance_methods.include?(name.to_s) and
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name !~ /^(__|instance_eval)/
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@hidden_methods ||= {}
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@hidden_methods[name.to_sym] = instance_method(name)
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def find_hidden_method(name)
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@hidden_methods ||= {}
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@hidden_methods[name] || superclass.find_hidden_method(name)
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# Redefine a previously hidden method so that it may be called on a blank
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unbound_method = find_hidden_method(name)
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fail "Don't know how to reveal method '#{name}'" unless unbound_method
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define_method(name) do |*args|
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bound_method ||= unbound_method.bind(self)
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bound_method.call(*args)
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instance_methods.each { |m| hide(m) }
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######################################################################
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# Since Ruby is very dynamic, methods added to the ancestors of
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# BlankSlate <em>after BlankSlate is defined</em> will show up in the
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# list of available BlankSlate methods. We handle this by defining a
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# hook in the Object and Kernel classes that will hide any method
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# defined after BlankSlate has been loaded.
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alias_method :blank_slate_method_added, :method_added
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# Detect method additions to Kernel and remove them in the
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def method_added(name)
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result = blank_slate_method_added(name)
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return result if self != Kernel
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######################################################################
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# Same as above, except in Object.
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alias_method :blank_slate_method_added, :method_added
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# Detect method additions to Object and remove them in the
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def method_added(name)
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result = blank_slate_method_added(name)
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return result if self != Object
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def find_hidden_method(name)
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######################################################################
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# Also, modules included into Object need to be scanned and have their
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# instance methods removed from blank slate. In theory, modules
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# included into Kernel would have to be removed as well, but a
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# "feature" of Ruby prevents late includes into modules from being
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# exposed in the first place.
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alias blankslate_original_append_features append_features
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def append_features(mod)
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result = blankslate_original_append_features(mod)
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return result if mod != Object
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instance_methods.each do |name|
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BlankSlate.hide(name)
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