The Objective Ruby Style Guide

This is a work in progress, send pulls, create issues, argue with me etc.

This style guide makes no effort to improve readability which is to a large extent subjective and hard to measure.

The Objective Ruby Style Guide aims to provide guidance on Ruby coding style that is based on objective fact and real benefits over more subjective reasons such as "I've always done it that way" or "I prefer the way that looks".

The guide will not apply to declarative DSL code.

Goals

Consistency

If there are two alternatives for an expression, like quotes for example, pick one for an objective reason and use that one all the time.

Reduce churn

Style that results in code that can be added to or modified by simply adding lines rather than changing existing ones will be preferred.

Reduce use of keywords

In Ruby everything is an object and almost everything is a method. This gives great power to its users. This style guide will favour use of Ruby's methods over its more mysterious keywords which often bypass calling methods you perhaps thought should be called.

This has the side effect of increased use of blocks which are an awesome Ruby feature.

Quoted strings

Always use double quotes.

More complex strings

Always use %{"a string that is maybe a quote"}.

Passing Blocks

Always use { }, never use do; end

• Text editors are MUCH better at understanding braces
• Chaining and functional operations are clearer
• Imperative operations like #each do not suffer

Receiving a block and yielding

Always capture blocks and invoke with #call.

• Capture blocks with &block at the end of the method signature
• Invoke them with #call passing yielded values as an argument
• Test for presence with if block rather than block_given?

This provides a consisent signal that a block argument is used over inspecting the method implementation for the yield keyword. Invokation with #call and presence test with if block enforce that blocks are always captured.

# Objectively inferior
def do_something_and_yield
  do_something
  yield if block_given?
end

# Objectively superior
def do_something_and_yield(&block)
  do_something
  block.call if block
end

Collections

Spread collections across multiple lines

Always define collections across multiple lines, giving each element its own line. Elements must not share lines with their containing tokens [{(.

Always add a trailing comma to the last element.

# Objectively inferior
[ "one", "two", "three" ]

# Objectively superior
[
  "one",
  "two",
  "three",
]

Hashes

Never use the #[] accessor method, Always use #fetch and #store.

hash = { kitteh: "o hai" }

# Objectively inferior
doge = hash[:doge]

doge.so_fetching

# Some time later somewhere else in the code
# =>  undefined method `so_fetching' for nil:NilClass (NoMethodError)

# Objectively superior
hash.fetch(:doge).so_fetching

# Immediately raises
# `fetch': key not found: :doge (KeyError)

Methods

def keyword

Never use the def keyword. Always use #define_method.

# Objectively inferior
def a_method(*args)
  nil # LOL
end

# Objectively superior
define_method(:a_method) { |*args|
  nil # LOL
}

• One way to define methods, statically and dynamincally
• Uses a method rather than a keyword
• Methods are defined with blocks which means every method is a lexically scoped closure

Parentheses

Always use paretheses when defining or calling a method which has arguments.

Never use paretheses when the method has no arguments.

Classes

Definition / class keyword

Never use the class keyword, Always use Class.new

# Objectively inferior
class Thing
  # ...
end

# Objectively superior
Thing = Class.new {
  # ...
}

• When anonymous classes need to be defined your syntax is the same
• More Ruby (better language transparency / less VM Magic)
• Forces you think about classes as objects

Re-opening

Crazy programmers like to reopen classes. When the urge is too much, keep to the no class keyword rule, instead use #class_eval.

# Objectively inferior
class Thing
  # I re-opened u but I can't even tell LOL
end

# Objectively superior
Thing.class_eval {
  # I re-opened u for sure ROFL
}

• Definition and re-opening cannot be confused
• Does not use any keywords

Constants

Never use class constants, instead define instance methods that return a new copy of your constant literals each time.

# Objectively inferior
class Thing
  VALUES = { one: "one" }.freeze
end

# Objectively superior
Thing = Class.new {
  define_method(:one) {
    {
      one: "one",
    }
  }
}

• Even when frozen, inner values of the constant can be mutated
• Anything at a static or class level should be avoided in an OO system

Namespacing and modules

Similarly to classes, use Module.new for definition and Module.module_eval to re-open.

Module and class constuctors yield themselves into the block, using this yielded value is better than using self as self isn't lexically scoped.

MyThings = Module.new { |things|
  things::Thing = Class.new { |klass|
    # class body
  }
}

Inheritance

Prefer object composition, avoid the super keyword.

The recommended syntax for inheritance is

Thing = Class.new(SuperThing) {
  # ... specializations
}

Structs

Never inherit from a Struct. Struct.new actually returns a new anonymous class instance in the same way Class.new does.

# Objectively inferior
class ValueObject < Struct.new(:one, :two, :three)
  VALUES = { one: "one" }.freeze
end

# Objectively superior
ValueObject = Struct.new(:one, :two, :three) {
  define_method(:some_behaviour) {
    # ooooh behave
  }
}