TIL: Ruby and Rails Knowledges 1

What I Learned

After a couple of months working with Rails, I am summarizing some of the useful things I have learned about Ruby and Rails.

Safe Navigation Operator

Introduced in Ruby 2.3.0, the safe navigation operator (&.) prevents undefined method for nil:NilClass errors. It is similar to the try method in Rails.

With it you can write:

user&.address&.zip

instead of:

if user
  user.address.zip
else
  nil
end

Alternatives

When only the first item in a chain is nullable, you can use && instead of &. to more accurately express intent.

user && user.address.zip

Beyond just using different syntax, there is also an opportunity to refactor. The chain of non-nullable methods can safely be extracted out, which typically results in cleaner code and also satisfies the Law of Demeter.

class User
  def zip
    address.zip
  end
end

Dynamically Define a Method

define_method defines an instance method on the receiver. The method parameter can be a Proc, a Method, or an UnboundMethod object. If a block is given, it is used as the method body.

from apidock

class Product
  class << self
    [:name, :brand].each do |attribute|
      define_method :"find_by_#{attribute}" do |value|
        all.find {|prod| prod.public_send(attribute) == value }
      end
    end
  end
end

Ruby freeze

freeze()

Prevents further modifications to an object. A RuntimeError will be raised if a modification is attempted. There is no way to unfreeze a frozen object. See also Object#frozen?.

from apidock

str = "this is string"
str.freeze

str.replace("this is new string") #=> FrozenError (can't modify frozen String)
or
str[0] #=> 't'
str[0] = 'X' #=> FrozenError (can't modify frozen String)

Retrospect

JavaScript has something similar to Ruby's safe navigation operator. However, define_method is especially powerful for specific use cases like the factory pattern, and makes for a very clean API. freeze can be found in many languages. What I learned here is how to handle constants inside a class. In JavaScript I typically reached for enums, but they were not always the smoothest solution.

These are small parts of Ruby and Rails, and I am still getting used to them. I hope to write Ruby and Rails fluently while following community conventions.

Well Done!