How to implement options hashes in Ruby?

Question

How can I implement options hashes? How is the structure of a class that has option hashes in it? Say I have a person class. I want to implement a method such as my_age that when called upon will tell me my age using options hashes.

Answer 1

You could do something like this:

class Person

  def initialize(opts = {})
    @options = opts
  end

  def my_age
    return @options[:age] if @options.has_key?(:age)
  end

end

and now you're able to call to the age like this

p1 = Person.new(:age => 24)<br/>
p2 = Person.new

p1.my_age # => 24<br/>
p2.my_age # => nil

Answer 2

class Person
  def birth_date
    Time.parse('1776-07-04')
  end

  def my_age(opts=nil)
    opts = {
      as_of_date: Time.now, 
      birth_date: birth_date,
      unit: :year
    }.merge(opts || {})
    (opts[:as_of_date] - opts[:birth_date]) / 1.send(opts[:unit])
  end
end

Answer 3

Might be worth mentioning that Ruby 2.1 adds the ability to pass in keyword arguments that don't need to be in a particular order AND you can make them be required or have default values.

Ditching the options hash reduces the boilerplate code to extract hash options. Unnecessary boilerplate code increases the opportunity for typos and bugs.

Also with keyword arguments defined in the method signature itself, you can immediately discover the names of the arguments without having to read the body of the method.

Required arguments are followed by a colon while args with defaults are passed in the signature as you'd expect.

For example:

class Person
  attr_accessor(:first_name, :last_name, :date_of_birth)

  def initialize(first_name:, last_name:, date_of_birth: Time.now)   
    self.first_name = first_name
    self.last_name = last_name
    self.date_of_birth = date_of_birth
  end

  def my_age(as_of_date: Time.now, unit: :year)
    (as_of_date - date_of_birth) / 1.send(unit)
  end
end

Answer 4

In Ruby 2.x you can use ** operator:

class Some
  def initialize(**options)
    @options = options
  end

  def it_is?
    return @options[:body] if @options.has_key?(:body)
  end
end