did_you_know.ruby?

ivo anjo
ruby ninja @ talkdesk

Let's talk function arguments

get_contacts(10, true)



...?

Documentation!!!

get_contacts(
  start_from: 10,
  has_address: true,
)

get_contacts(10, true)

Less derping/bugs!!!

Extensibility!!!

get_contacts(10, true,
  nil, nil, :married)

??????????

When to use
...my rules of 👍

Now srsly

How to code 'em

def get_contacts(options = {})
  start_from = 
    options.fetch(:start_from)
  has_address = 
    options.fetch(:has_address)

Ruby >= 2.1

Kudos to the ones already updated, you rock guys!

def get_contacts(
  start_from:, has_address: true)

Variable Args?

Yes, you can (still) do this!

def get_contacts(**options)
  start_from = 
    options.fetch(:start_from)

And it has a name!
**double splat**

You can combine with positional stuff

def print_hello(name, language:)
  # ...
end

print_hello('Joe',
  language: 'en_US')

The most complex method signature you will ever see

def foo(a, *b, c = true, d:,
  e: true, **f, &block)

The most complex method signature you will ever see

def foo(a, *b, c = true, d:,
  e: true, **f, &block)

d ➡️ required keyword

e ➡️ optional keyword

f ➡️ vararg keyword

The most complex method signature you will ever see

def foo(a, *b, c = true, d:,
  e: true, **f, &block)

block ➡️ duh

def foo(a, *b, c = true, d:,
  e: true, **f, &block)

foo('a', 'b1', 'b2', 'b3', false,
  d: 'd', e: false, f1: 'f1',
  f2: 'f2') do puts 'Hello!' end

These rules (mostly) apply to blocks too

def foo
  yield a:1
end

foo do |a:, b: 2|
  puts a + b
end

But wait, there's more!

class Foo
  def self.print(options = {})
    name = options.fetch(:name)
    puts name
  end
  def self.print_joe
    print(user: 'Joe')
  end
end

Yay, my spec passes!

Nevermind the code actually being broken

class Foo
  def self.print(options = {})
    name = options.fetch(:name)
    puts name
  end

  def self.print_joe
    print(user: 'Joe')
  end
end

Rspec knows kung-fu

...and keyword args

def self.print(name:)
  puts name
end

That brings me to rspec doubles

d = double('Foo', print: nil)

d.print(user: 'Joe')

...verifying doubles!

d = class_double('Foo',
      print: nil)

d.print(user: 'Joe')

Keyword args are just an example

Verifying doubles check number of positional args and if the method exists too. 

https://relishapp.com/rspec/rspec-mocks/v/3-4/docs/verifying-doubles

IF YOU REMEMBER ANYTHING

Keyword arguments
&
Verifying doubles

Oh and I almost forgot to tell you can use splat like this

rgb = [:red,  :green,   :blue]
cmy = [:cyan, :magenta, :yellow]

colors =
  [:white, :black, *rgb, *cmy]

# colors is now 
[:white, :black, :red, :green,
 :blue, :cyan, :magenta, :yellow]

And you can use it on method calls too

def do_stuff(a, b, c)
  # ...
end

some_args = ['b', 'c']

do_stuff('a', *some_args)

You can do the same with the double splat

def do_stuff(a:, b:, c:)
  # ...
end

some_args =
  {b: "not_the_b's", c: 'c'}

do_stuff(a: 'a', **some_args)

Merging hashes like a sir

def build_event(data, meta)
  {**data, **meta}
end

To really confuse you, I'm going back to rspec again

class Bar
  def self.hello
    message = 
      ENV['MESSAGE'] || 'hello'
    puts message
  end
end

describe '#hello' do
  it 'prints hello' do
    expect(Bar).to \
     receive(:puts).with('hello')
    Bar.hello
  end

Nice! Time to open that PR

Well I fixed it and re-ran the specs

Random spec ordering! ... :| ?


Well, how do I debug this???

Ask me for help :)

Let's try this again: Ask **rspec** for help

$ bundle exec rspec --bisect
Bisect started
Running suite to find failures... (0.16527
seconds)
Starting bisect with 1 failing example and 
1 non-failing example.
Checking that failure(s) are order-dependent
... failure appears to be order-dependent

Bisect complete! Reduced necessary non-fail
ing examples from 1 to 1 in 0.15835 seconds.

The minimal reproduction command is:
  rspec ./bar_spec.rb[1:1:1,1:1:2]

Especially useful when issue is cross-spec 

interference

Pry is your friend

irb is dead to me

You can use it to debug too

require 'pry'; binding.pry

Inspect, interact, call, ...

ls -- list methods and variables

show-source: where does this come from, and what is it?

It has tab completion!
Such tabbing!

break/step/next/finish/continue/frame/...

...using pry-byebug

gem 'pry'

# <-- just add this to gemfile
gem 'pry-byebug'

rubular.com for all your regexp stuffies

Shiny stuff you can do with Ruby 2.3

# You can simplify this

foo && foo.bar && foo.bar.baz

Ruby & Threads

Ruby & Threads

• be careful with threads and threaded webservers (puma)
• common mistake: require is *NOT* thread-safe -- don't use it in the middle of a method!!!!

Oh and FYI on Rubies

Tired yet?

Friendly reminder:

Ruby 2.3.1 is out

Ruby < 2.1 is EOL 

UPGRADE YOUR RUBY

Get Elixir today

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git

Thanks!
You guys r awesome



learned lots from y'all