ruby

See A melhor maneira que encontrei para aprender Ruby.

[TOC]

Ruby Basics

Basic Data Types

Numeric
- Integer
- Float
String
Boolean
Array
Hashes - it's like a associative array

Don't forget: everything in Ruby is an object!

Coding Style

Variables and Methods named with snake_case.

Methods

def hello(name)
  return "Hi #{name}!" # note: this return is optional
end

puts hello("meleu") # => "Hi meleu!"


# TODO: explain this '&' notation
# convert to string and convert to integer
"5 1 4 2 3 15 42 34".split.map(&:to_i)
# => [5, 1, 4, 2, 3, 15, 42, 34]

Blocks

Block styles

# do/end style
5.times do
  puts "Hello, World!"
end

# bracket style
5.times{ puts "Hello, World!" }

Blocks are passed to methods. In the examples above 👆 we're giving to the method 5.times the instructions we want to run each time.

Think of blocks as anonymous functions that can take zero or more arguments.

There are many methods that accept blocks, like gsub:

>> "augusto 'meleu' lopes".gsub("u"){ puts "Found an U!" }
Found an U!
Found an U!
Found an U!
=> "agsto 'mele' lopes"

Block Parameters

When our instructions within a block need to reference the value that they're currently working with, we can specify a block parameter inside | pipe characters:

5.times do |i|
  puts "#{i}: Hello, World!"
end

Conditionals

if age > 18
  return "You can vote"
else
  return "Sorry, you're too young to vote"
end

Loops

for loops:

for i in 0..10 do
  puts i
end

# iterating over each item of an array
array.each do |n|
  puts n
end

# iterating over each key of a hash
hash.each_key do |key|
  puts n
end
# note: .each_value works similarly

# iterating over each key,value pair of a hash
hash.each do |key, value|
  puts "#{key} => #{value}"
end

tutorials

Ruby in 100 Minutes
Navigating Ruby Files with Vim
http requests
- https://www.twilio.com/blog/5-ways-make-http-requests-ruby
- https://www.rubyguides.com/2018/08/ruby-http-request/

Some ruby tricks

# from char to ASCII value
'a'.ord # ordinal
# => 97

# from ASCII value to char
97.chr
# => "a"


# you can "subtract" arrays like this
[1, 2, 3] - [1, 3]
# => [2]


# get the lowest and biggest value in an array
[5, 1, 4, 2, 3].minmax
# => [1, 5]
# you can also use .min and .max


# repeat a string
"meleu " * 3
# => "meleu meleu meleu "

Custom `irb` prompt for copy'n'pasting

Put this in your ~/.irbrc:

IRB.conf[:PROMPT][:COPYNPASTE] = { # name of prompt mode
  :AUTO_INDENT => true,  # enables auto-indent mode
  :PROMPT_I => nil,      # simple prompt
  :PROMPT_S => nil,      # prompt for continuated strings
  :PROMPT_C => nil,      # prompt for continuated statement
  :RETURN => "# => %s\n" # format to return value
}

IRB.conf[:PROMPT_MODE] = :COPYNPASTE

Instrumentation

https://opentelemetry.io/docs/instrumentation/ruby/getting-started/