Key Takeaways from The Well-Grounded Rubyist

+
+Some time ago, I wrote about my journey into Ruby and how "The Well-Grounded Rubyist" helped me to get a better understanding of the language. I took a lot of notes while reading the book, and I think it's time to share some of them. This is not a comprehensive review, but rather a collection of interesting tidbits and concepts that stuck with me.
+
+My first post about the book.
+
+

The Object Model

+
+One of the most fascinating aspects of Ruby is its object model. The book does a great job of explaining the details.
+
+

Everything is an object (almost)

+
+In Ruby, most things are objects. This includes numbers, strings, and even classes themselves. This has some interesting consequences. For example, you can't use i++ like in C or Java. Integers are immutable objects. 1 is always the same object. 1 + 1 returns a new object, 2.
+
+

The self keyword

+
+There is always a current object, self. If you call a method without an explicit receiver, it's called on self. For example, puts "hello" is actually self.puts "hello".
+
+ +

# At the top level, self is the main object
+p self
+# => main
+p self.class
+# => Object
+
+def foo
+  # Inside a method, self is the object that received the call
+  p self
+end
+
+foo
+# => main
+

+
+This code demonstrates how self changes depending on the context. At the top level, it's main, an instance of Object. When foo is called without a receiver, it's called on main.
+
+

Singleton Methods

+
+You can add methods to individual objects. These are called singleton methods.
+
+ +

obj = "a string"
+
+def obj.shout
+  self.upcase + "!"
+end
+
+p obj.shout
+# => "A STRING!"
+
+obj2 = "another string"
+# obj2.shout would raise a NoMethodError
+

+
+Here, the shout method is only available on the obj object. This is a powerful feature for adding behavior to specific instances.
+
+

Classes are Objects

+
+Classes themselves are objects, instances of the Class class. This means you can create classes dynamically.
+
+ +

MyClass = Class.new do
+  def say_hello
+    puts "Hello from a dynamically created class!"
+  end
+end
+
+instance = MyClass.new
+instance.say_hello
+# => Hello from a dynamically created class!
+

+
+This shows how to create a new class and assign it to a constant. This is what happens behind the scenes when you use the class keyword.
+
+

Control Flow and Methods

+
+The book clarified many things about how methods and control flow work in Ruby.
+
+

case and the === operator

+
+The case statement is more powerful than I thought. It uses the === (threequals or case equality) operator for comparison, not ==. Different classes can implement === in their own way.
+
+ +

# For ranges, it checks for inclusion
+p (1..5) === 3 # => true
+
+# For classes, it checks if the object is an instance of the class
+p String === "hello" # => true
+
+# For regexes, it checks for a match
+p /llo/ === "hello" # => true
+
+def check(value)
+  case value
+  when String
+    "It's a string"
+  when (1..10)
+    "It's a number between 1 and 10"
+  else
+    "Something else"
+  end
+end
+
+p check(5) # => "It's a number between 1 and 10"
+

+
+

Blocks and yield

+
+Blocks are a cornerstone of Ruby. You can pass them to methods to customize their behavior. The yield keyword is used to call the block.
+
+ +

def my_iterator
+  puts "Entering the method"
+  yield
+  puts "Back in the method"
+  yield
+end
+
+my_iterator { puts "Inside the block" }
+# Entering the method
+# Inside the block
+# Back in the method
+# Inside the block
+

+
+This simple iterator shows how yield transfers control to the block. You can also pass arguments to yield and get a return value from the block.
+
+ +

def with_return
+  result = yield(5)
+  puts "The block returned #{result}"
+end
+
+with_return { |n| n * 2 }
+# => The block returned 10
+

+
+This demonstrates passing an argument to the block and using its return value.
+
+

Fun with Data Types

+
+Ruby's core data types are full of nice little features.
+
+

Symbols

+
+Symbols are like immutable strings. They are great for keys in hashes because they are unique and memory-efficient.
+
+ +

# Two strings with the same content are different objects
+p "foo".object_id
+p "foo".object_id
+
+# Two symbols with the same content are the same object
+p :foo.object_id
+p :foo.object_id
+
+# Modern hash syntax uses symbols as keys
+my_hash = { name: "Paul", language: "Ruby" }
+p my_hash[:name] # => "Paul"
+

+
+This code highlights the difference between strings and symbols and shows the convenient hash syntax.
+
+

Arrays and Hashes

+
+Arrays and hashes have a rich API. The %w and %i shortcuts for creating arrays of strings and symbols are very handy.
+
+ +

# Array of strings
+p %w[one two three]
+# => ["one", "two", "three"]
+
+# Array of symbols
+p %i[one two three]
+# => [:one, :two, :three]
+

+
+A quick way to create arrays. You can also retrieve multiple values at once.
+
+ +

arr = [10, 20, 30, 40, 50]
+p arr.values_at(0, 2, 4)
+# => [10, 30, 50]
+
+hash = { a: 1, b: 2, c: 3 }
+p hash.values_at(:a, :c)
+# => [1, 3]
+

+
+The values_at method is a concise way to get multiple elements.
+
+

Final Thoughts

+
+These are just a few of the many things I learned from "The Well-Grounded Rubyist". The book gave me a much deeper appreciation for the language and its design. If you are a Ruby programmer, I highly recommend it. Meanwhile, I also read the book "Programming Ruby 3.3", just I didn't have time to process my notes there yet.
+
+E-Mail your comments to paul@nospam.buetow.org :-)
+
+Other Ruby-related posts:
+
+2021-07-04 The Well-Grounded Rubyist
+
+Back to the main site
+

Key Takeaways from The Well-Grounded Rubyist

The Object Model

Everything is an object (almost)

The self keyword

Singleton Methods

Classes are Objects

Control Flow and Methods

case and the === operator

Blocks and yield

Fun with Data Types

Symbols

Arrays and Hashes

Final Thoughts

Key Takeaways from The Well-Grounded Rubyist

The Object Model

Everything is an object (almost)

The self keyword

Singleton Methods

Classes are Objects

Control Flow and Methods

case and the === operator

Blocks and yield

Fun with Data Types

Symbols

Arrays and Hashes

Final Thoughts

Gemtexter 2.1.0 - Let's Gemtext again³

Table of Contents

Why Bash?

Switch to GPL3 license

Source code highlighting support

HTML exact variant

Use of Hack webfont by default

HTML Mastodon verification support

More

To be in the .zone!