lessons-learned-ruby.md

Lessons learned using Ruby

• Method lookup
• Complex regular expressions
• Exceptions
• Memoization in accessors
• &:symbol - Symbol to Proc / &Proc - Proc to Block / Block to Proc
• dup vs. clone
• Enumerator and Enumerable
• Docker
• Rubocop
• SQL - PostgreSQL
• Setup Ruby in VSCode

Method lookup

Complex regular expressions

Use regex literals with the x option:

%r{
    <regex_part_1> # you can add comments
    <regex_part_2> # and end of lines
}x

Exceptions

• rescue without a class will capture StandardError and its children.

  • It won't capture Ruby internal errors, which is fine most of the time.

• raise with no current exception in $! will raise a RuntimeError (which is a child of StandardError).

Docs: https://docs.ruby-lang.org/en/master/Exception.html

Memoization in accessors

• Use memoization in accessors when needed.

  def some_attribute
    @some_attribute ||= some_network_call
  end

  To avoid calling the network again if the first time it returned nil or false:

  def some_attribute
    return @some_attribute if defined? @some_attribute
    @some_attribute = some_network_call
  end

• To avoid making your code unreadable, use gems that do memoization for you.

Docs: https://www.justinweiss.com/articles/4-simple-memoization-patterns-in-ruby-and-one-gem/

&:symbol - Symbol to Proc / &Proc - Proc to Block / Block to Proc

Look at these specs:

hamax97.github.io/write-ups/ruby/&_operator_with_procs.rb

Lines 1 to 37 in 398236c

	RSpec.configure do |config|
	config.default_formatter = "doc"
	end
	RSpec.describe "'&' operator in the context of procs" do
	context "when applied to a symbol" do
	it "sends 'to_proc' to the symbol" do
	def some_method(&block)
	expect(block).to match a_kind_of Proc
	end
	some_method(&:each)
	end
	end
	context "when applied to a method's argument" do
	it "converts the block given to a Proc" do
	def some_method(&block)
	expect(block).to match a_kind_of Proc
	end
	some_method do
	# nothing
	end
	end
	end
	context "when applied to a Proc" do
	it "converts the Proc into a block" do
	def some_method
	yield
	end
	some_method(&lambda {})
	end
	end
	end

dup vs. clone

Look at these specs:

hamax97.github.io/write-ups/ruby/dup_vs_clone.rb

Lines 1 to 94 in 29c070c

	RSpec.configure do |config|
	config.default_formatter = "doc"
	config.alias_example_to :they
	end
	RSpec.describe "dup vs. clone" do
	they "both create shallow copies" do
	arr = %w[an array of strings]
	dup_arr = arr.dup
	clone_arr = arr.clone
	expect(dup_arr.object_id).not_to eq arr.object_id
	expect(clone_arr.object_id).not_to eq arr.object_id
	arr_object_ids = arr.map(&:object_id)
	# the objects inside the array are not copied, only their references.
	expect(dup_arr.map(&:object_id)).to contain_exactly(*arr_object_ids)
	expect(clone_arr.map(&:object_id)).to contain_exactly(*arr_object_ids)
	end
	describe "dup" do
	context "copies without special attributes" do
	it "ignores freezed status" do
	str = "some constant string".freeze
	dup_str = str.dup
	expect(str).to be_frozen
	expect(dup_str).not_to be_frozen
	end
	it "ignores tainted status" do
	skip "can't find a way to create a tainted object"
	# Objects created from external sources are marked as tainted.
	# Any object derived from this object is marked as tainted.
	obj = ENV["GEM_HOME"]
	dup_obj = obj.dup
	expect(obj).to be_tainted
	expect(dup_obj).not_to be_tainted
	end
	it "ignores singleton class" do
	obj = %w[some kind of object]
	def obj.method_in_singleton_class
	# this method goes to obj's singleton class.
	end
	dup_obj = obj.dup
	expect(obj).to respond_to(:method_in_singleton_class)
	expect(dup_obj).not_to respond_to(:method_in_singleton_class)
	end
	end
	end
	describe "clone" do
	context "copies the object as it is (including special attributes)" do
	it "copies freezed status" do
	str = "some constant string".freeze
	clone_str = str.clone
	expect(str).to be_frozen
	expect(clone_str).to be_frozen
	end
	it "copies tainted status" do
	skip "can't find a way to create a tainted object"
	# Objects created from external sources are marked as tainted.
	# Any object derived from this object is marked as tainted.
	obj = ENV["GEM_HOME"]
	clone_obj = obj.clone
	expect(obj).to be_tainted
	expect(clone_obj).not_to be_tainted
	end
	it "copies singleton class" do
	obj = %w[some kind of object]
	def obj.method_in_singleton_class
	# this method goes to obj's singleton class.
	end
	clone_obj = obj.clone
	expect(obj).to respond_to(:method_in_singleton_class)
	expect(clone_obj).to respond_to(:method_in_singleton_class)
	end
	end
	end
	end

Enumerator and Enumerable

TODO: Complete this.

Docker

Create a container to test things:

docker run --rm -it -h myruby --name myruby -v $(pwd):/myapp ruby:3.2.0 /bin/bash

Rubocop

To disable cops or entire departments in specific places of your codebase:

• Disable in a section of code:

# rubocop:disable Layout/LineLength, Style
[..]
# rubocop:enable Layout/LineLength, Style

• Disable all cops in a section of code:

# rubocop:disable all
[..]
# rubocop:enable all

• Disable cops or departments in a single line:

for x in (0..10) # rubocop:disable Style/For

• Disable cops or departments using the .rubocop.yml file:

Style/StringLiterals:
  Enabled: false

AllCops:
  Exclude:
    - 'docs/**/'

SQL - PostgreSQL

Spin up a container with PostgreSQL:

docker run --name mypostgresql -d -p 15432:5432 -v mypostgresql:/var/lib/postgresql/data -e POSTGRES_HOST_AUTH_METHOD=trust postgres

Setup Ruby in VSCode

Extensions:

• vscode-ruby by Peng Lv.
• Ruby Solargraph by Castwide.
• Rails Run Specs by Peter Negrei.
• Go to Spec by Lourenci.
• Endiwse.
• ERB Linter.
• ESLint (for JavaScript code).
• Auto Close Tag.
• Github Theme.
• Material Theme Icons.
• vscode-gemfile.
• Ruby Test Explorer.
• Trailing Spaces.
• Auto Markdown TOC.
• VSCode vim, or VSCode Neovim.
• TODO: For debugging?

Gems:

• bundler
• solargraph
• rubocop

Generate solargraph default config file:

bundle exec solargraph config

Settings file .vscode/settings.json:

{
    "solargraph.useBundler": true,
    "solargraph.checkGemVersion": false,
    "ruby.lint": {
        "rubocop": {
            "useBundler": true
        }
    },
    "ruby.format": "rubocop",
    "ruby.useBundler": true,
    "auto-close-tag.disableOnLanguage": ["markdown"],
    "ruby.specCommand": "bin/rspec",
    "ruby.specFocusTerminal": false,
    "ruby.specSaveFile": true,
    "markdown-toc.depthFrom": 2,
    "files.insertFinalNewline": true
}

Key shortcuts:

• Go to Spec extension:

  • Go to spec of file: Ctrl + Shift + T.

• Rails Run Specs extension:

  • Run All Specs: Ctrl + Windows + r.
  • Run File Specs: Ctrl + Windows + t.
  • Run Spec Line: Ctrl + Windows + l.
  • Run Last Spec: Ctrl + Windows + y.