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Metaprogramming? Not good enough! Justin Weiss @justinweiss | #tinyobj

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Metaprogramming? Not good enough! Justin Weiss @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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→ 2005: Ruby @justinweiss | #tinyobj

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→ 2005: Ruby → 2006: JavaScript Ruby @justinweiss | #tinyobj

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→ 2005: Ruby → 2006: JavaScript Ruby → 2007: Erlang Ruby @justinweiss | #tinyobj

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→ 2005: Ruby → 2006: JavaScript Ruby → 2007: Erlang Ruby → ... → 2015: Swift Ruby @justinweiss | #tinyobj

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What makes Ruby, Ruby? @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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Erlang = Actors @justinweiss | #tinyobj

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Erlang = Actors Haskell = Monads @justinweiss | #tinyobj

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Erlang = Actors Haskell = Monads Lisp = Parentheses @justinweiss | #tinyobj

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Erlang = Actors Haskell = Monads Lisp = Parentheses Macros @justinweiss | #tinyobj

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Erlang = Actors Haskell = Monads Lisp = Parentheses Macros Ruby = Metaprogramming? @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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Metaprogramming → !? @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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A brand new object model (on top of Ruby) @justinweiss | #tinyobj

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Object model The concepts, data structures, and methods you use to build things in your language @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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I. Piumarta and A. Warth Open, Extensible Object Models http://piumarta.com/software/cola/ objmodel2.pdf @justinweiss | #tinyobj

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When you have a method name and arguments, which code do you use? @justinweiss | #tinyobj

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When you have a method name and arguments, which code do you use? @justinweiss | #tinyobj

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def lookup(object, method_name) # Look up a method by name in object's methods list # If it exists, return it # Otherwise, if you have a parent class, recurse end @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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What is behavior? @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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Object = a thing Class = a thing that builds objects, holds methods, has a parent Behavior = a thing that holds methods like lookup and add_method @justinweiss | #tinyobj

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Object add_method lookup @justinweiss | #tinyobj

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How do we get an object from a class? @justinweiss | #tinyobj

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Object add_method lookup build_object @justinweiss | #tinyobj

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What about new classes, sub-classes, or sub- behaviors? @justinweiss | #tinyobj

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Object add_method lookup build_object delegate @justinweiss | #tinyobj

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How do you call a method? @justinweiss | #tinyobj

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Object add_method lookup build_object delegate send @justinweiss | #tinyobj

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Let's build it in Ruby! @justinweiss | #tinyobj

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class TinyObject < BasicObject attr_accessor :state attr_accessor :behavior end @justinweiss | #tinyobj

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class TinyObject < BasicObject attr_accessor :state attr_accessor :behavior end @justinweiss | #tinyobj

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Create the core methods @justinweiss | #tinyobj

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behavior_add_method = lambda do |behavior, method_name, method| behavior.state[:methods][method_name] = method end @justinweiss | #tinyobj

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behavior_add_method = lambda do |behavior, method_name, method| # -------^ behavior.state[:methods][method_name] = method end @justinweiss | #tinyobj

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behavior_lookup = lambda do |behavior, method_name| # ... end @justinweiss | #tinyobj

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behavior_lookup = lambda do |behavior, method_name| # Look up a method by name in the object's methods list method = behavior.state[:methods][method_name] # ... method end @justinweiss | #tinyobj

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behavior_lookup = lambda do |behavior, method_name| # ... # If you can't find it, but have a parent class... if !method && behavior.state[:parent] # call this method recursively, using the parent instead method = behavior_lookup.call(behavior.state[:parent], method_name) end method end @justinweiss | #tinyobj

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behavior_lookup = lambda do |behavior, method_name| # Look up a method by name in the object's methods list method = behavior.state[:methods][method_name] # If you can't find it, but have a parent class... if !method && behavior.state[:parent] # call this method recursively, using the parent instead method = behavior_lookup.call(behavior.state[:parent], method_name) end method end @justinweiss | #tinyobj

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behavior_build_object = lambda do |behavior| # Allocate an object obj = TinyObject.new obj.state = {} # set the object's class / behavior # to yourself (the class that called this method) obj.behavior = behavior # return the object obj end @justinweiss | #tinyobj

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behavior_delegate = lambda do |parent_class| # ... end @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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subclass = behavior_build_object.call(parent_class.behavior) @justinweiss | #tinyobj

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# set the object's parent (in its state) to ourselves subclass.state[:parent] = parent_class # initialize the object's state with an empty set of methods subclass.state[:methods] ||= {} subclass @justinweiss | #tinyobj

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behavior_delegate = lambda do |parent_class| parent_class_behavior = parent_class && parent_class.behavior subclass = behavior_build_object.call(parent_class_behavior) # set the object's parent (in its state) to ourselves subclass.state[:parent] = parent_class # initialize the object's state with an empty set of methods subclass.state[:methods] ||= {} subclass end @justinweiss | #tinyobj

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TinyObject: Our object structure, containing behavior and state behavior_add_method: Add a method to a class behavior_lookup: Find an implementation, from a method name behavior_build_object: Like .new, build an object from a class / behavior behavior_delegate: Inherit from a class / behavior @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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default_behavior = behavior_delegate.call(nil) # ... @justinweiss | #tinyobj

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default_behavior = behavior_delegate.call(nil) default_behavior.behavior = default_behavior @justinweiss | #tinyobj

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root_object_class = behavior_delegate.call(nil) root_object_class.behavior = default_behavior @justinweiss | #tinyobj

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root_object_class = behavior_delegate.call(nil) root_object_class.behavior = default_behavior @justinweiss | #tinyobj

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# ... default_behavior.state[:parent] = root_object_class @justinweiss | #tinyobj

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default_behavior = behavior_delegate.call(nil) default_behavior.behavior = default_behavior root_object_class = behavior_delegate.call(nil) root_object_class.behavior = default_behavior default_behavior.state[:parent] = root_object_class @justinweiss | #tinyobj

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behavior_add_method.call(default_behavior, "lookup", behavior_lookup) behavior_add_method.call(default_behavior, "add_method", behavior_add_method) behavior_add_method.call(default_behavior, "build_object", behavior_build_object) behavior_add_method.call(default_behavior, "delegate", behavior_delegate) @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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object_send = lambda do |object, method_name, *args| method = find_method.call(object, method_name) if method method.call(object, *args) else raise "No method #{method_name} found on object" end end @justinweiss | #tinyobj

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find_method = lambda do |object, method_name| object_send.call(object.behavior, "lookup", method_name) end @justinweiss | #tinyobj

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find_method = lambda do |object, method_name| if (object == default_behavior && method_name == "lookup") behavior_lookup.call(default_behavior, "lookup") else object_send.call(object.behavior, "lookup", method_name) end end @justinweiss | #tinyobj

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behavior_add_method: Add a method to a class behavior_lookup: Find an implementation, from a method name behavior_build_object: Like .new, build an object from a class / behavior behavior_delegate: Inherit from a class / behavior object_send: Call a method, by name, on an object @justinweiss | #tinyobj

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greeter_class = object_send.call(root_object_class, "delegate") @justinweiss | #tinyobj

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greeter_class = object_send.call(root_object_class, "delegate") object_send.call(greeter_class, "add_method", "hello", lambda { |object| puts "Hello, world!" }) @justinweiss | #tinyobj

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greeter = object_send.call(greeter_class, "build_object") object_send.call(greeter, "hello") # => @justinweiss | #tinyobj

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greeter = object_send.call(greeter_class, "build_object") object_send.call(greeter, "hello") # => "Hello, world!" @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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greeter = object_send.call(greeter_class, "build_object") object_send.call(greeter, "hello") # => "Hello, world!" @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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class TinyObject < BasicObject attr_accessor :state attr_accessor :behavior def method_missing(name, *args) object_send = nil behavior = self.behavior # Crawl our ancestors for an "object_send" implementation while !object_send && behavior object_send = behavior.state[:methods]["object_send"] behavior = behavior.state[:parent] end # Call object_send on ourselves object_send.call(self, name.to_s, *args) end end @justinweiss | #tinyobj

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object_send.call(greeter, "hello") @justinweiss | #tinyobj

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object_send.call(greeter, "hello") ⬇ greeter.hello @justinweiss | #tinyobj

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behavior_add_method.call(root_object_class, "object_send", object_send) @justinweiss | #tinyobj

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greeter_class.add_method("hello_name", lambda { |object| puts "Hello, #{object.state[:name]}!" }) # ----^ @justinweiss | #tinyobj

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alice = greeter_class.build_object bob = greeter_class.build_object alice.state[:name] = "Alice" bob.state[:name] = "Bob" alice.hello_name # => bob.hello_name # => @justinweiss | #tinyobj

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alice = greeter_class.build_object bob = greeter_class.build_object alice.state[:name] = "Alice" bob.state[:name] = "Bob" alice.hello_name # => "Hello, Alice!" bob.hello_name # => "Hello, Bob!" @justinweiss | #tinyobj

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Now what? @justinweiss | #tinyobj

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Log method calls! @justinweiss | #tinyobj

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def lookup # Get the old lookup method from the parent of our behavior # Call it to find the real method implementation # Wrap the method and return it end @justinweiss | #tinyobj

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method_logger = lambda do |method_name, method, *args| puts "> Calling #{method_name}... " method.call(*args) puts "> Done!" end @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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intercepting_behavior = default_behavior.delegate @justinweiss | #tinyobj

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intercepting_behavior.add_method( "lookup", lambda do |sender, method_name| # Get the old lookup method from the parent of our class's behavior lookup = object_send.call(sender.behavior.state[:parent], "lookup", "lookup") # Call it to find the real method implementation method = lookup.call(sender, method_name) # Wrap the method and return it if method original_method = method interceptor = sender.state[:interceptor_method] method = lambda { |*args| interceptor.call(method_name, original_method, *args) } end method end ) @justinweiss | #tinyobj

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# Get the old lookup method # from the parent of our class's behavior super_behavior = ? lookup = super_behavior.lookup("lookup") @justinweiss | #tinyobj

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super_behavior = sender.behavior.state[:parent] lookup = super_behavior.lookup("lookup") @justinweiss | #tinyobj

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# Get the old lookup method # from the parent of our class's behavior super_behavior = sender.behavior.state[:parent] lookup = super_behavior.lookup("lookup") # Call lookup to find the real method implementation method = lookup.call(sender, method_name) @justinweiss | #tinyobj

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# Wrap the method and return it if method original_method = method interceptor = sender.state[:interceptor_method] method = lambda do |*args| interceptor.call(method_name, original_method, *args) end end method @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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person_class = root_object_class.delegate # ... @justinweiss | #tinyobj

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person_class = root_object_class.delegate person_class.behavior = intercepting_behavior @justinweiss | #tinyobj

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person_class = root_object_class.delegate # ... @justinweiss | #tinyobj

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person_class = root_object_class.delegate person_class.behavior = intercepting_behavior @justinweiss | #tinyobj

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method_logger = lambda do |method_name, method, *args| puts "> Calling #{method_name}... " method.call(*args) puts "> Done!" end person_class.state[:interceptor_method] = method_logger @justinweiss | #tinyobj

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person_class.add_method "name", lambda { |_| puts "Justin" } person_class.add_method "location", lambda { |_| puts "Cincinnati, OH" } @justinweiss | #tinyobj

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person = person_class.build_object person.name # # # person.location # # # @justinweiss | #tinyobj

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person = person_class.build_object person.name # > Calling name... # Justin # > Done! person.location # > Calling location... # Cincinnati, OH # > Done! @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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person_class.behavior = default_behavior person.name # @justinweiss | #tinyobj

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person_class.behavior = default_behavior person.name # Justin @justinweiss | #tinyobj

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Retry method calls! @justinweiss | #tinyobj

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person_class.add_method("flaky_method", lambda do |_| if rand(3) == 0 puts "Success!" true else false end end) @justinweiss | #tinyobj

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retry_interceptor = lambda do |method_name, method, *args| until method.call(*args) puts "Method #{method_name} failed, retrying..." sleep 0.5 end end @justinweiss | #tinyobj

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person_class.state[:interceptor_method] = retry_interceptor person.flaky_method @justinweiss | #tinyobj

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person_class.state[:interceptor_method] = retry_interceptor person.flaky_method # Method flaky_method failed, retrying... @justinweiss | #tinyobj

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person_class.state[:interceptor_method] = retry_interceptor person.flaky_method # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... @justinweiss | #tinyobj

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person_class.state[:interceptor_method] = retry_interceptor person.flaky_method # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... @justinweiss | #tinyobj

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person_class.state[:interceptor_method] = retry_interceptor person.flaky_method # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... @justinweiss | #tinyobj

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person_class.state[:interceptor_method] = retry_interceptor person.flaky_method # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... # Method flaky_method failed, retrying... # Success! @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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Multiple Inheritance @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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multiple_parents_behavior = default_behavior.delegate @justinweiss | #tinyobj

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multiple_parents_behavior.add_method("add_parent", lambda do |behavior, new_parent| # Initialize `parents` with the original parent unless behavior.state[:parents] behavior.state[:parents] = [] parent = behavior.state[:parent] behavior.state[:parents] << parent if parent end # Append the new parent to `parents` behavior.state[:parents] << new_parent end ) @justinweiss | #tinyobj

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multiple_parents_behavior.add_method( "lookup", lambda do |behavior, method_name| method = behavior.state[:methods][method_name] parents = behavior.state[:parents] || [behavior.state[:parent]] if !method && parents parents.each do |parent| break if method = parent.lookup(method_name) end end method end ) @justinweiss | #tinyobj

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multiple_parents_behavior.add_method( "lookup", lambda do |behavior, method_name| method = behavior.state[:methods][method_name] parents = behavior.state[:parents] || [behavior.state[:parent]] if !method && parents parents.each do |parent| # v---- -----^ break if method = parent.lookup(method_name) end end method end ) @justinweiss | #tinyobj

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person_class = root_object_class.delegate person_class.add_method "name", lambda { |_| puts "Justin" } greeter_class = root_object_class.delegate greeter_class.add_method "greeting", lambda { |_| puts "Hello! Hello! Hello!" } @justinweiss | #tinyobj

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social_person_class = person_class.delegate social_person_class.behavior = multiple_parents_behavior social_person_class.add_parent(greeter_class) @justinweiss | #tinyobj

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justin = social_person_class.build_object justin.name # => justin.greeting # => @justinweiss | #tinyobj

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justin = social_person_class.build_object justin.name # => "Justin" justin.greeting # => "Hello! Hello! Hello!" @justinweiss | #tinyobj

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→ Single inheritance → Interception → Multiple Inheritance @justinweiss | #tinyobj

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→ Object → add_method → lookup → build_object → delegate → send @justinweiss | #tinyobj

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Modules? method_missing? BasicObject? delegation? @justinweiss | #tinyobj

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Intent @justinweiss | #tinyobj

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What's normal? @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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What? Why!? @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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The best way to understand a system is to break it. @justinweiss | #tinyobj

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symbols.each do |symbol| klass = Class.new(ActiveRecord::Base) do def method_missing(name, *args) # ... end end Object.const_set(symbol.to_s.capitalize, klass) end @justinweiss | #tinyobj

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@justinweiss | #tinyobj

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@justinweiss | #tinyobj

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Try it out @justinweiss | #tinyobj

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Thank you! Justin Weiss @justinweiss https://www.avvo.com justin@justinweiss.com https://www.justinweiss.com/ rubyconf-2016 @justinweiss | #tinyobj

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Thank you! Justin Weiss @justinweiss https://www.avvo.com justin@justinweiss.com https://www.justinweiss.com/ rubyconf-2016 @justinweiss | #tinyobj

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The Ruby logo is Copyright © 2006, Yukihiro Matsumoto. It is licensed under the terms of the Creative Commons Attribution- ShareAlike 2.5 License agreement. "Happy Programmers" by Jesper Rønn-Jensen, used under CC BY- SA 2.0 / Resized from original "Laptop Stickers" by Nate Angell, used under CC BY 2.0 / Resized from original "No Brain" by Pierre-Olivier Carles, used under CC BY 2.0 @justinweiss | #tinyobj