The fewer the concepts, the better the code?

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@davetron5000 The Fewer the Concepts, The Better The Code Dave Copeland / @davetron5000

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@davetron5000 The Fewer the Concepts, The Better The Code Dave Copeland / @davetron5000

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@davetron5000 Justin

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@davetron5000 Code Reviews Justin Justin Me Me COOL WHY DID YOU DO IT THAT WAY? MY CODE IS SIMPLER! THE CYCLOMATIC COMPLEXITY IS LOWER, THERE ARE FEWER INTERMEDIATE VARIABLES, AND BY USING LIST COMPREHENSIONS I'VE MADE THE ENTIRE THING MUCH LESS COMPLEX AND THEREFORE EASIER TO UNDERSTAND, SO WHY AM I EXPLAINING THIS?!?!??!

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@davetron5000 Code does not exist in a vaccuum

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@davetron5000 All code exists within some context

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@davetron5000 All code exists within some context • What is it for? • How important is it that it works perfectly? • How often is it going to change? • Who is in charge of maintaining it? • Who might some day need to change it?

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@davetron5000 Code Metrics Ignore Context

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@davetron5000 cart1.rb class Cart def total @line_items.select(&:in_stock?).map { |line_item| line_item.price * line_item.quantity }.reduce(&:+) end end

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@davetron5000 Rubocop Metrics Metric cart1.rb MethodLength 3 AbcSize 6 CyclomaticComplexity 1 PerceivedComplexity 1 Number of statements, branches, and conditionals. Count of branches or # of paths through the code Different way to look at paths through the code

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@davetron5000 cart2.rb class Cart def total total_price = 0 for line_item in @line_items do if line_item.in_stock? cost = line_item.price * line_item.quantity total_price = total_price + cost end end return total_price end end

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@davetron5000 Rubocop Metrics Metric cart1.rb cart2.rb MethodLength 3 8 AbcSize 6 6.71 CyclomaticComplexity 1 3 PerceivedComplexity 1 3

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@davetron5000 How can we quantify the context of who is (or could be) working on this code?

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@davetron5000 What if we counted all the things you have to know to understand the code?

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@davetron5000 cart1.rb concepts class Cart def total @line_items.select(&:in_stock?).map { |line_item| line_item.price * line_item.quantity }.reduce(&:+) end end

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@davetron5000 cart1.rb concepts • class • def • @line_items • . • * • select, map, reduce • &:in_stock? • Why you can do that with plus • { creates a block • | deﬁnes params • How does the return value get sorted?

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@davetron5000 Metrics Metric cart1.rb cart2.rb MethodLength 3 8 AbcSize 6 6.71 CyclomaticComplexity 1 3 PerceivedComplexity 1 3 # of Concepts 13

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@davetron5000 cart2.rb concepts class Cart def total total_price = 0 for line_item in @line_items do if line_item.in_stock? cost = line_item.price * line_item.quantity total_price = total_price + cost end end return total_price end end

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@davetron5000 cart2.rb concepts • class • def • @line_items • . • * • + • for • if • return

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@davetron5000 Metrics Metric cart1.rb cart2.rb MethodLength 3 8 AbcSize 6 6.71 CyclomaticComplexity 1 3 PerceivedComplexity 1 3 # of Concepts 13 9

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@davetron5000 It requires less knowledge to understand the second code listing, even though metrics tell us it's more complex

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@davetron5000 Which code is "better"?

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@davetron5000 What does "better" even mean?

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@davetron5000 What do we do with code? Write Change Read

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@davetron5000 We mostly need to understand what it does Write Understand

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@davetron5000 All things being equal, code whose behavior is easier to understand is better than code whose behavior is harder to understand

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@davetron5000 Understand…by who?

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@davetron5000 –No True Scotsman “Any Rubyist should know that stuff”

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@davetron5000 –Survivorship Bias “Anyone could learn this stuff”

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@davetron5000 Josh

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@davetron5000 Josh's Contributions Josh Josh WTF Code I Wrote That Was "Less Complex" Code Justin Wrote That Was "Less Fancy" I GET IT

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@davetron5000 Look at these concepts • class • def • @line_items • . • * • select, map, reduce • &:in_stock? • Why you can do that with plus • { creates a block • | deﬁnes params • How does the return value get sorted?

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@davetron5000 But look at these concepts • class • def • @line_items • . • * • + • for • if • return

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@davetron5000 The "more complex" code requires fewer concepts to understand and the concepts it does require are more universal

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@davetron5000 Understanding Author Team Org Rubyists Programmers More Valuable / Better

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@davetron5000 How learnable are these things? • For any programmer? • For a programmer who knows an OO language? • For a Ruby programmer? • With a year of experience? • With 20 years experience?

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@davetron5000 Your code, and the concepts required to understand it, paint a picture of who can be on your team

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@davetron5000 Try this on your next PR • How many new concepts does this change introduce? • Does everyone on the team understand these concepts? • How hard are they to learn if you already understand the code before the change? • Did we decrease the number of people who could understand this code?

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@davetron5000 add_tax1.diff @@ -1,12 +1,24 @@ class Cart + TAX_RATES = Hash.new(0.45).tap { |hash| + hash[:dc] = 0.1 + hash[:ca] = 0.05 + hash[:va] = 0.03 + } + def total total_price = 0 for line_item in @line_items do if line_item.in_stock? cost = line_item.price * line_item.quantity - total_price = total_price + cost + tax = cost * TAX_RATES[@shipping_state] + total_price = total_price + cost + tax end end return total_price end end • Constants • Hash.new • [ ] • tap

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@davetron5000 add_tax2.diff @@ -1,12 +1,31 @@ class Cart def total total_price = 0 for line_item in @line_items do if line_item.in_stock? cost = line_item.price * line_item.quantity - total_price = total_price + cost + tax = cost * tax_rate(@shipping_state) + total_price = total_price + cost + tax end end return total_price end + + def tax_rate(shipping_state) + if shipping_state == :dc + return 0.1 + end + if shipping_state == :ca + return 0.05 + end + if shipping_state == :va + return 0.03 + end + return 0.45 + end end • ==

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@davetron5000 Metrics Metric cart2.rb diff1 diff2 MethodLength 8 9 9 10 AbcSize 6.71 9.64 9.64 6 CyclomaticComplexity 3 3 3 4 PerceivedComplexity 3 3 3 4 # of Concepts 9 13 (+4) 10 (+1)

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@davetron5000 –Various Doctrines & Manifestos “But you are ignoring the power of these tools. These SHARP KNIVES!”

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@davetron5000 Sharp…or shiny?

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@davetron5000 triangle_spec.rb describe Triangle do subject { Triange.new(3,3,3) } it { is_expected.to be_isoscoles.and be_equilateral } end

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@davetron5000 triangle_spec.rb class TriangeTest < TestCase def test_isoscoles triangle = Triangle.new(3,3,3) assert triangle.isoscoles? end def test_equilateral triangle = Triangle.new(3,3,3) assert triangle.equilateral? end end

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@davetron5000 conﬁg/routes.rb resources :messages do resources :comments end resources :articles do resources :comments end

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@davetron5000 conﬁg/routes.rb concern :commentable do resources :comments end resources :messages, concerns: :commentable resources :articles, concerns: :commentable

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@davetron5000 conﬁg/routes.rb def commentable_resource(resource) resources resource do resources :comments end end commentable_resource(:messages) commentable_resource(:articles)

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@davetron5000 Still…abstractions are good, right? They reduce errors, ossify conventions, and let us go faster.

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@davetron5000 Who is on the team matters. Who can and cannot easily join the team matters.

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@davetron5000 Adding a concept, bringing in a new feature, adding a library, carries one of two possible costs:

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@davetron5000 The cost to bring everyone along, or the cost of leaving some behind

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@davetron5000 Like everything, it's a tradeoff. But you should make it with eyes open.

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@davetron5000

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@davetron5000 But the complexity of the domain, the system, the deployment…who cares about the code?!

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@davetron5000 Server Next Level Complexity Most metrics are about code, not systems method method class method method class method method class method method class app app DB Load Balancer CDN Cache Code Metrics Analysis Code Metrics Analysis

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@davetron5000 # of concepts, who knows them, who could learn them— is fractal

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@davetron5000 controller1.rb def mau Customer.signed_up. with_order("created_at > ?",1.year.ago). paid. count end SELECT COUNT(*) from CUSTOMERS WHERE .....

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@davetron5000 controller2.rb def mau ActiveRecord::Base.connection.execute(" SELECT COUNT(*) FROM customers JOIN orders ON orders.customer_id = customers.id WHERE ... ")[0][0] end SELECT COUNT(*) from CUSTOMERS WHERE .....

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@davetron5000 Monolith vs. Microservices

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@davetron5000 The Metrics you have aren't bad, but… • What do you have to know to work on the system? • Who is being left behind? • Are you committed to bringing them along? • If you aren't or can't…maybe ﬁnd a solution with fewer concepts required.

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@davetron5000 sustainable-rails.com