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module Arel
module Visitors
class Visitor
def initialize
@dispatch = get_dispatch_cache
end
def accept object
visit object
end
private
def self.dispatch_cache
Hash.new do |hash, klass|
hash[klass] = "visit_#{(klass.name || '').gsub('::', '_')}"
end
end
def get_dispatch_cache
self.class.dispatch_cache
end
def dispatch
@dispatch
end
def visit object
send dispatch[object.class], object
rescue NoMethodError => e
raise e if respond_to?(dispatch[object.class], true)
superklass = object.class.ancestors.find { |klass|
respond_to?(dispatch[klass], true)
}
raise(TypeError, "Cannot visit #{object.class}") unless superklass
dispatch[object.class] = dispatch[superklass]
retry
end
end
end
end
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