Ruby

January 14, 2021

command line apps

http://blog.honeybadger.io/writing-command-line-apps-in-ruby/ - tutorial on command line apps in ruby

http://culttt.com/2015/07/01/creating-and-using-modules-in-ruby/ - using ruby modules

http://www.stuartellis.name/articles/rake/#using-other-ruby-libraries-in-rake-tasks - rake tasks

https://apidock.com/ruby/OptionParser - options parser doc

GSUB

https://stackoverflow.com/questions/16579223/using-named-capture-groups-inside-ruby-gsub-blocks-regex - capture groups in gsub

RVM

update rvm

rvm get stable --auto-dotfiles

list known ruby versions

rvm list known

list installed

rvm list

install ruby

rvm install ruby-2.5.1 # version 2.5.1
rvm install ruby --latest # latest stable version

create ruby-version

rvm --ruby-version use 2.5.1@my_app --create

install bundler && init

gem install bundler
bundle init

adding dependencies

bundle add pkg-config --version="~> 1.1"

dockerizing

Dockerizing Ruby Application

FROM ruby:2.5.1-alpine
ADD Gemfile /app/
ADD Gemfile.lock /app/
RUN apk --update add --virtual build-dependencies ruby-dev build-base && \
    gem install bundler --no-ri --no-rdoc && \
    cd /app ; bundle install --without development test && \
    apk del build-dependencies
ADD . /app
RUN chown -R nobody:nogroup /app
USER nobody
ENV RACK_ENV production
EXPOSE 9292
WORKDIR /app

https://medium.com/magnetis-backstage/how-to-cache-bundle-install-with-docker-7bed453a5800 - How to cache bundle install with Docker: While dockerizing a Rails app, the first problem that comes out is the slow bundle install command while building the app’s image.

https://github.com/BretFisher/jekyll-serve/blob/master/Dockerfile - working with jekyll

IDE Support

VSCode

https://medium.com/better-programming/code-like-a-pro-tooling-to-supercharge-vs-code-for-ruby-bf2ae61df5e3

  1. Install vscode extensions:

  2. Install two global gems. These are used by the IDE and have trouble using project level rvn installs.

    rvm @global do bundle update
rvm @global do gem install rubocop
rvm @global do gem install solargraph

  3. Configure VSCode User Settings:

    "ruby.codeCompletion": "rcodetools",
"ruby.format": "rubocop",
"ruby.intellisense": "rubyLocate",
"ruby.useBundler": true, //run non-lint commands with bundle exec
"ruby.useLanguageServer": true, // use the internal language server (see below)
"ruby.lint": {
    "rubocop": {
    "useBundler": true // enable rubocop via bundler
    },
    "reek": {
    "useBundler": true // enable reek via bundler
    }
}

  4. Restart IDE

Style and Lint

https://rubystyle.guide/#guiding-principles

Enforcing with rubocop

https://docs.rubocop.org/rubocop/0.87/index.html

https://medium.com/@kirill_shevch/lint-your-ruby-code-with-overcommit-and-static-analysis-tools-bd36d3147d2e

  1. Add these gems to your project.

        gem 'debase', '~> 0.2.1', group: :development
    gem 'overcommit', '~> 0.54.0'
    gem 'rubocop', require: false

    Run

    bundle install

  2. Configure IDE

  3. Setup overcommit

    overcommit --install
overcommit --sign

  4. Setup rubocop

    rubocop --auto-gen-config
rubocop -a -x

  5. Edit overcommit config, enable rubocop

    PreCommit:
  RuboCop:
    enabled: true

  6. Hooks will now run on commits

Files, I/O

Blocks, Procs & Lamdas

Special operators

[[1,2,3,4],[1,2,3,4],[1,2,3,4]].map(&:join)
#  => ["1234", "1234", "1234"]

# same as:
[[1,2,3,4],[1,2,3,4],[1,2,3,4]].map { |v| v.join('') }
#  => ["1234", "1234", "1234"]

Printing

puts

  • Special side effect of returning nil after printing
  • Adds newline
  • puts "yo".inspect is the same as p "yo" and will return the value after printing

print

  • print string without extra line

inspect returns a string of the object

Method Conventions

? methods that end in ? return a boolean

Safe Navigation

  • account&.owner&.address will get the address if owner exists on account

Control Flow

  • if, else, elsif basic if
  • puts "Strings are empty" if x.empty? inline if statement
  • unless is a negated if, or opposite of if.

Boolean

  • !, !!, &&, || boolean tests
  • !!nil will return false, it is the only object that will do that
  • !!0 will return true, like most

symbols and hash rocket

  • :name is a symbol
  • name: is only valid in a literal hash
  • { :name => 'blah'} is the hash rocket syntax
  • { name: 'blah' } is a literal hash
  • "data-turbo-track": "reload" and { "data-turbo-track": "reload" } are same, {} are optional, like parenthesis

*Splat and Double **Splat

Destructure array, object, hash

arr = [1,2,3]
first, second, third = *arr
pp first # 1
pp second # 2
first, *rest, last = [1,2,3,4,5]
pp first # 1
pp rest # [2,3,4]
pp last # 5

h = ["first": 1, "second": 2, "third": 3]
first, second, third = **h
pp first # 1
pp second # 2

Whitespace

Ruby doesn't distinguish between whitespace and others like '\n', you can break lines on char length

Classes

< inheritance self is optional in a class.

Lambda

-> stabby lambda

-> { puts "foo" } # proc output
-> { puts "foo" }.call # foo, returns nil

Math

When working with numbers if any number is a float it will use float precision.

  • 3 / 2 returns 1
  • 3 / 2 returns 1.5

Stats

def calc_stats(array, round_digits = 2)
  n = array.size
  mean = array.sum.to_f / n.to_f
  squared_differences = array.map { |x| (x - mean) ** 2 }
  variance = squared_differences.sum / n

  {
    min: array.min.round(round_digits),
    max: array.max.round(round_digits),
    mean: mean.round(round_digits),
    standard_deviation: Math.sqrt(variance).round(round_digits)
  }
end

Looping over arrays

  • [*(1..20)].each_slice(3) { |c| pp c } will break the array into groups of 3 and loop through. The last value will have two items.

Writing Files

def write_to_csv(filename, overwrite: true)
  file = "tmp/data-details/#{filename}"
  Dir.mkdir("tmp/data-details") unless File.exists?("tmp/data-details")
  mode = overwrite ? "w+" : "a+"
  action_text = overwrite ? "Writing" : "Appending"

  puts "#{action_text} to #{file}"
  CSV.open(file, mode, headers: true, converters: [:float, :integer, :date]) do |csv|
    yield csv
  end
end

write_to_csv(filename, overwrite: overwrite) do |csv|
    csv << [
      "Name",
      "Min",
      "Max",
      "Mean",
      "Standard Deviation"
    ] if overwrite
end

Exceptions

https://rollbar.com/guides/ruby/how-to-handle-exceptions-in-ruby/