Code Smells: Your Refactoring Cheat Codes

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Code Smells: r Refactoring Cheat Codes

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@jpignata

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Code smells are heuristics for refactoring.

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Our design communicates to us through resistance.

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Our code is difficult to understand

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Our code is difficult to test

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Our code is difficult to change

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Our code is difficult to reuse

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This resistance is valuable feedback.

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Code smells are hints from our software about how to reduce this resistance.

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This is one way our design emerges.

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Application Push Daemon Google Cloud Messaging API Android Device UDP HTTPS

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Application Push Daemon Google Cloud Messaging API Android Device UDP HTTPS

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queue = Queue.new client = HTTPClient.new socket = UDPSocket.new 10.times do Thread.new do while data = queue.pop client.post("https://android.googleapis.com/gcm/send", data, { "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" }) end end end socket.bind("0.0.0.0", 6889) while data = socket.recvfrom(4096) case data[0].split.first when "PING" socket.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) queue << json end end

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PING it responds with PONG SEND it delivers the message to the Google Cloud Messaging API Commands

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$ ruby ./pushd.rb

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$ nc -u 127.0.0.1 6889 PING

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$ nc -u 127.0.0.1 6889 PING PONG

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PING ✔ it responds with PONG SEND it delivers the message to the Google Cloud Messaging API Commands

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$ nc -u 127.0.0.1 6889 SEND AP91bQd65Z5IA8p "Steve: What is up?"

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PING ✔ it responds with PONG SEND ✔ it delivers the message to the Google Cloud Messaging API Commands

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describe "Push Daemon" do let(:socket) { UDPSocket.new } before(:all) do Thread.new { load "./pushd.rb" } end describe "commands" do describe "PING" do it "responds with PONG" end describe "SEND" do it "delivers the message to the Google Cloud Messaging API" end end end

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it "responds with PONG" do socket.send("PING", 0, "127.0.0.1", 6889) response, _ = socket.recvfrom(8) response.should eq("PONG") end

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it "delivers the message to the Google Cloud Messaging API" do stub_request :post, "https://android.googleapis.com/gcm/send" socket.send('SEND t0k3n "Steve: What is up?"', 0, "127.0.0.1", 6889) assert_requested :post, "https://android.googleapis.com/gcm/send", { body: { "registration_ids" => ["t0k3n"], "data" => { "alert" => "Steve: What is up?" } }.to_json } end

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jp@oeuf:~/workspace/mwrc(master)$ rspec Push Daemon commands PING responds with PONG SEND delivers the message to the Google Cloud Messaging API Finished in 0.06854 seconds 2 examples, 0 failures

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Long Method C S

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queue = Queue.new client = HTTPClient.new socket = UDPSocket.new

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10.times do Thread.new do while data = queue.pop # ... end end end

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client.post("https://android.googleapis.com/gcm/send", data, { "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" })

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socket.bind("0.0.0.0", 6889)

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case data[0].split.first when "PING" # ... when "SEND" # ... end end

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data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } })

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Replace Method with Method Object R f r

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class PushDaemon end

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class PushDaemon def initialize @queue = Queue.new @client = HTTPClient.new @socket = UDPSocket.new end end

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10.times do Thread.new do while json = queue.pop client.post("https://android.googleapis.com/gcm/send", json, "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" ) end end end socket.bind("0.0.0.0", 6889) while data = socket.recvfrom(4096) case data[0].split.first when "PING" socket.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) queue << json end end

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def start 10.times do Thread.new do while json = @queue.pop @client.post("https://android.googleapis.com/gcm/send", json, "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" ) end end end @socket.bind("0.0.0.0", 6889) while data = @socket.recvfrom(4096) case data[0].split.first when "PING" @socket.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @queue << json end end end

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Extract Method R f r

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def start spawn_workers bind loop { process_request } end

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def spawn_workers 10.times do Thread.new do while json = @queue.pop @client.post("https://android.googleapis.com/gcm/send", json, "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" ) end end end end

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def bind @socket.bind("0.0.0.0", 6889) end

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def process_request data = @socket.recvfrom(4096) case data[0].split.first when "PING" @socket.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @queue << json end end

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class PushDaemon def initialize @queue = Queue.new @client = HTTPClient.new @socket = UDPSocket.new end def start spawn_workers bind loop { process_request } end private def spawn_workers; end def bind; end def process_request; end end

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➡ Update authorization key ➡ Increase thread pool size ➡ Swap HTTP client ➡ Use a different transport protocol ➡ Modify wire protocol format ➡ Add commands ➡ Add a different push notification service ➡ Move UDP port ➡ Use x-www-form-urlencoded instead of JSON ➡ Lower maximum payload size ➡ Bind to a specific interface address ➡ Update push service URL

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Divergent Change C S

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Extract Class R f r

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class Worker def initialize @queue = Queue.new @client = HTTPClient.new end end

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class PushDaemon def initialize @queue = Queue.new @client = HTTPClient.new @socket = UDPSocket.new end end

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class PushDaemon def initialize @worker = Worker.new @socket = UDPSocket.new end end

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class Worker def initialize @queue = Queue.new @client = HTTPClient.new end def <<(json) @queue << json end end

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def spawn_workers 10.times do Thread.new do while json = @queue.pop @client.post("https://android.googleapis.com/gcm/send", json, { "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" }) end end end end

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class Worker def initialize @queue = Queue.new @client = HTTPClient.new end def spawn(count) count.times do Thread.new do while json = @queue.pop @client.post("https://android.googleapis.com/gcm/send", json, { "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" }) end end end end def <<(json) @queue << json end end

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class PushDaemon def initialize @worker = Worker.new @socket = UDPSocket.new end def start spawn_workers bind loop { process_request } end private def spawn_workers; end def bind; end def process_request; end end

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class PushDaemon def initialize @worker = Worker.new @socket = UDPSocket.new end def start @worker.spawn(10) bind loop { process_request } end private def bind; end def process_request; end end

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class PushDaemon def initialize @worker = Worker.new @socket = UDPSocket.new end def start @worker.spawn(10) bind loop { process_request } end private def bind; end def process_request; end end

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def bind @socket.bind("0.0.0.0", 6889) end def process_request data = @socket.recvfrom(4096) case data[0].split.first when "PING" @socket.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end [ Bind [ Receive [ Send

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class UDPServer def initialize @socket = UDPSocket.new end end

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class UDPServer def initialize @socket = UDPSocket.new end def bind(port) @socket.bind("0.0.0.0", port) end def receive @socket.recvfrom(4096) end def send(message, address, port) @socket.send(message, 0, address, port) end end

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class PushDaemon def initialize @worker = Worker.new @socket = UDPSocket.new end def start @worker.spawn(10) bind loop { process_request } end private def bind; end def process_request; end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new end def start @worker.spawn(10) bind loop { process_request } end private def bind; end def process_request; end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new end def start @worker.spawn(10) bind loop { process_request } end private def bind; end def process_request; end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new end def start @worker.spawn(10) @server.bind(6889) loop { process_request } end private def process_request; end end

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def process_request data = @server.receive case data[0].split.first when "PING" @server.send("PONG", data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @queue << json end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new end def start @worker.spawn(10) @server.bind(6889) loop { process_request } end private def process_request data = @server.receive case data[0].split.first when "PING" @server.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end end

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Inappropriate Intimacy C S

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PushDaemon UDPServer bind(port) receive data

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PushDaemon UDPServer listen(port) call(data)

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.bind(6889) loop { process_request } end private def process_request data = @server.receive case data[0].split.first when "PING" @server.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.bind(6889) @server.listen end private def process_request data = @server.receive case data[0].split.first when "PING" @server.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end private def process_request data = @server.receive case data[0].split.first when "PING" @server.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def process_request(data) case data[0].split.first when "PING" @server.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def call(data) case data[0].split.first when "PING" @server.send("PONG", 0, data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end end

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class UDPServer def initialize(app) @app = app @socket = UDPSocket.new end def bind(port) @socket.bind("0.0.0.0", port) end def receive @socket.recvfrom(4096) end def send(message, address, port) @socket.send(message, 0, address, port) end end

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class UDPServer def initialize(app) @app = app @socket = UDPSocket.new end def listen(port) @socket.bind("0.0.0.0", port) loop { @app.call(receive) } end def receive @socket.recvfrom(4096) end def send(message, address, port) @socket.send(message, 0, address, port) end end

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Case Statement C S

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Replace Conditional with Polymorphism R f r

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def call(data) case data[0].split.first when "PING" @server.send("PONG", data[1][3], data[1][1]) when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end

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module Jobs class Ping def initialize(data, server) @data = data @server = server end def run @server.send("PONG", @data[1][3], @data[1][1]) end end end

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def call(data) case data[0].split.first when "PING" Jobs::Ping.new(data, @server).run when "SEND" data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) @worker << json end end

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module Jobs class Send def initialize(data, server) @data = data @server = server end def run @data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) end end end

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def call(data) case data[0].split.first when "PING" Jobs::Ping.new(data, @server).run when "SEND" json = Jobs::Send.new(data, @server).run @worker << json end end

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module Jobs class Send def self.client @client ||= HTTPClient.new end def initialize(data, server) @data = data @server = server end def run @data[0][5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) self.class.client.post("https://android.googleapis.com/gcm/send", json, { "Authorization" => "key=AIzaSyCABSTd47XeIH-ERx9rvHUSF9DIJ7DCwdk", "Content-Type" => "application/json" }) end end end

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class Worker def initialize @queue = Queue.new end def spawn(count) count.times do Thread.new { work } end end def <<(job) @queue << job end private def work while job = @queue.pop job.run end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def call(data) case data[0].split.first when "PING" Jobs::Ping.new(data, @server).run when "SEND" json = Jobs::Send.new(data, @server).run @worker << json end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def call(data) job = case data[0].split.first when "PING" Jobs::Ping.new(data, @server) when "SEND" Jobs::Send.new(data, @server) end if job @worker << job end end end

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Move Creation Knowledge to Factory R f r

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.bind(6889) @server.listen end def call(data) job = case data[0].split.first when "PING" Jobs::Ping.new(data, @server) when "SEND" Jobs::Send.new(data, @server) end if job @worker << job end end end

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module Jobs def self.factory(data, server) case data[0].split.first when "PING" Jobs::Ping.new(data, server) when "SEND" Jobs::Send.new(data, server) end end end

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module Jobs JOBS = { "PING" => Ping, "SEND" => Send } def self.factory(data, server) command = data[0].split.first.upcase klass = JOBS[command] if klass klass.new(data, server) end end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def call(data) job = Jobs.factory(data, @server) if job @worker << job end end end

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module Jobs class Ping def initialize(data, server) @data = data @server = server end def run @server.send("PONG", @data[1][3], @data[1][1]) end end end

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Data Clumps C S

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["PING", ["AF_INET", 61370, "localhost", "127.0.0.1"]] data[1][3] data[1][1] [ [

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class Client def initialize(sockaddr) @addrinfo = Addrinfo.new(sockaddr) end def address @addrinfo.ip_address end def port @addrinfo.ip_port end end

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class UDPServer def initialize(app) @app = app @socket = UDPSocket.new end def listen(port) @socket.bind("0.0.0.0", port) loop do message, sockaddr = @socket.recvfrom(4096) client = Client.new(sockaddr) @app.call(client, message) end end def send(message, address, port) @socket.send(message, 0, address, port) end end

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Uncommunicative Name C S

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def call(client, message) job = Jobs.factory(client, message, @server) if job @worker << job end end end

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module Jobs class Ping def initialize(client, message, server) @client = client @message = message @server = server end def run @server.send("PONG", @client.address, @client.port) end end end

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Feature Envy C S

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Extracted objects tend to attract behavior.

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class Client def initialize(sockaddr) @addrinfo = Addrinfo.new(sockaddr) end def address @addrinfo.ip_address end def port @addrinfo.ip_port end end

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class Client def initialize(sockaddr, server) @addrinfo = Addrinfo.new(sockaddr) @server = server end def address @addrinfo.ip_address end def port @addrinfo.ip_port end end

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class Client def initialize(sockaddr, server) @addrinfo = Addrinfo.new(sockaddr) @server = server end def send(message) @server.send(message, address, port) end def address @addrinfo.ip_address end def port @addrinfo.ip_port end end

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class UDPServer def initialize(app) @app = app @socket = UDPSocket.new end def listen @socket.bind("0.0.0.0", port) loop do message, sockaddr = @socket.recvfrom(4096) client = Client.new(sockaddr) @app.call(client, message) end end def send(message, address, port) @socket.send(message, 0, address, port) end end

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class UDPServer def initialize(app) @app = app @socket = UDPSocket.new end def listen @socket.bind("0.0.0.0", port) loop do message, sockaddr = @socket.recvfrom(4096) client = Client.new(sockaddr, self) @app.call(client, message) end end def send(message, address, port) @socket.send(message, 0, address, port) end end

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module Jobs class Ping def initialize(client, message, server) @client = client @message = message @server = server end def run @server.send("PONG", @client.address, @client.port) end end end

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module Jobs class Ping def initialize(client, message, server) @client = client @message = message @server = server end def run @client.send("PONG") end end end

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module Jobs class Ping def initialize(client, message, server) @client = client @message = message @server = server end def run @client.send("PONG") end end end

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module Jobs class Ping def initialize(client, message) @client = client @message = message end def run @client.send("PONG") end end end

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module Jobs class Send def self.client @client ||= HTTPClient.new end def initialize(client, message) @client = client @message = message end def run @message[5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) self.class.client.post("https://android.googleapis.com/gcm/send", json, { "Authorization" => "key=AIzaSyCABSTd47XeIH-ERx9rvHUSF9DIJ7DCwdk", "Content-Type" => "application/json" }) end end end

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Same Name, Different Meaning C S

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module Jobs class Send def self.client @client ||= HTTPClient.new end def initialize(client, message) @client = client @message = message end def run @message[5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) json = JSON.generate({ "registration_ids" => [$1], "data" => { "alert" => $2 } }) self.class.client.post("https://android.googleapis.com/gcm/send", json, { "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" }) end end end

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class PushNotification def self.client @client ||= HTTPClient.new end def initialize(registration_id, alert) @registration_id = registration_id @alert = alert end def deliver self.class.client.post("https://android.googleapis.com/gcm/send", to_json, "Authorization" => "key=AIzaSyCABSTd47XeIH", "Content-Type" => "application/json" ) end def to_json { "registration_ids" => [@registration_id], "data" => { "alert" => @alert } }.to_json end end

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module Jobs class Send def initialize(client, message) @client = client @message = message end def run @message[5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/) PushNotification.new($1, $2).deliver end end end

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Primitive Obsession C S

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We’re using simple data types to represent complex ideas.

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@message[5..-1].match(/([a-zA-Z0-9_\-]*) "([^"]*)/)

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COMMAND [parameters]

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parameter “second parameter”

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Shellwords

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class Request def initialize(message) @tokens = Shellwords.split(message) end def command @tokens[0].to_s.upcase end def parameters Array(@tokens[1..-1]) end end

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class PushDaemon def initialize @worker = Worker.new @server = UDPServer.new(self) end def start @worker.spawn(10) @server.listen(6889) end def call(client, message) request = Request.new(message) job = Jobs.factory(client, request) if job @worker << job end end end

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module Jobs JOBS = { "PING" => Ping, "SEND" => Send } def self.factory(client, message) command = message.split.first.upcase klass = JOBS[command] if klass klass.new(client, message) end end end

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module Jobs JOBS = { "PING" => Ping, "SEND" => Send } def self.factory(client, request) klass = JOBS[request.command] if klass klass.new(client, request) end end end

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module Jobs class Send def initialize(client, request) @client = client @request = request end def run PushNotification.new(registration_id, alert).deliver end private def registration_id @request.parameters[0] end def alert @request.parameters[1] end end end

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Nil Checks C S

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module Jobs JOBS = { "PING" => Ping, "SEND" => Send } def self.factory(client, request) klass = JOBS[request.command] if klass klass.new(client, request) end end end Possible nil from hash [

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class PushDaemon def initialize @server = UDPServer.new(self) @worker = Worker.new end def start @worker.spawn(10) @server.listen(6889) end def call(client, message) request = Request.new(message) job = Jobs.factory(client, request) if job @worker << job end end end Possible nil from factory [

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nil communicates that an unknown command has been requested

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Introduce Null Object R f r

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module Jobs class NullJob def initialize(client, request) end def run end end end

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module Jobs JOBS = { "PING" => Ping, "SEND" => Send } def self.factory(client, request) klass = JOBS[request.command] if klass klass.new(client, request) end end end

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module Jobs JOBS = { "PING" => Ping, "SEND" => Send } JOBS.default = NullJob def self.factory(client, request) JOBS[request.command].new(client, request) end end

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module Jobs class Ping def initialize(client, request) @client = client @request = request end def run @client.send("PONG") end def >>(worker) worker << self end end end

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module Jobs class NullJob def initialize(client, request) end def run end def >>(worker) end end end