Effetive Ruby TLDR - part1

“Accustoming Yourself to Ruby”

#1. Understand What Ruby Considers To Be True

• Every value is trueexpect false and nil.
• The number 0 is ture in Ruby.
• Check if a value is nil with value#nil?.

#2. Treat All Objects As If They Could Be nil

• Only nil.nil? returns true.
• You can cast a nil to a empty string with nil.to_s or to a int with
  nil.to_i.

#3. Avoid Ruby’s Cryptic Perlisms

• Prefer String#match to str =~.
• Don’t modify global variables unless you must do.

#4. Be Aware That Constants Are Mutable

• Always freeze constant values to prevent them to be mutated.
• To prevent assigning new values to existing constants, freeze the module they
  are defined in.

#5. Pay attention to runtime warnings

• Use the -w CLI option to enable compile and runtime warnings. Or make it
  part of the RUBYOPT env variable.

Classes, Objects and Modules

#6. Know how ruby build inheritance hierarchies

• Method lookup algo - move right, then go up, that means when you clll a method
  foo.bar, you move to the right, find the class of the object foo, if you
  find bar in foo‘s class, then invoke it, or move to foo‘s superclass, do
  the same thing.
• If no method has been found, method_missing will be called with the same
  algo as above.
• Module are classes too. Including modules silently creates singleton classes
  which are inserted into the hierarchy above the including class.
• Class methods are just instance methods of the class’s metaclass

#7. Be Aware of the Different Behaviors of super

• Use super to call the overridden method.
• Use super with no args and no parentheses is equivalent to passing it all of
  the arguments which were given to the enclosing method.
• Use to super() to call overriden method withoug passing any arguments.

#8. Invoke super When Initializing Sub-classes

• Ruby doesn’t automatically call the initialize method in the superclass when
  creating objects from a subclass
• Call the overriden initialize method explicitly with super

#9. Be Alert for Ruby’s Most Vexing Parse

• Setter method must have a reciever, inside the class that defines it, the
  receiver should be self
• Avoid using self when call other methods inside a class.

#10. Prefer Struct to Hash for Structured Data

• When dealing with structured data which doesn’t quite justify a new class
  prefer using Struct to Hash.
• Assign the return value of Struct::new to a constant and treat that constant
  like a class.

Demo

User = Struct.new(:name, :age) # User.class = Class
user = User.new('kevin', 18)
puts user.name
user.age = 22