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Diffstat (limited to 'activerecord/lib/arel/visitors/visitor.rb')
-rw-r--r-- | activerecord/lib/arel/visitors/visitor.rb | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/activerecord/lib/arel/visitors/visitor.rb b/activerecord/lib/arel/visitors/visitor.rb new file mode 100644 index 0000000000..1c17184e86 --- /dev/null +++ b/activerecord/lib/arel/visitors/visitor.rb @@ -0,0 +1,42 @@ +# frozen_string_literal: true + +module Arel # :nodoc: all + module Visitors + class Visitor + def initialize + @dispatch = get_dispatch_cache + end + + def accept(object, *args) + visit object, *args + end + + private + + attr_reader :dispatch + + 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 visit(object, *args) + dispatch_method = dispatch[object.class] + send dispatch_method, object, *args + rescue NoMethodError => e + raise e if respond_to?(dispatch_method, 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 |