Caius Theory

Now with even more cowbell…

Some Small Refactorings in Ruby

Here’s a few things I refactor as I write code down initially. Not entirely convinced it’s strictly refactoring, but it’s how I amend from one pattern I see in a line or three of code into a different structure that I feel achieves the same result with cleaner or more concise code.

Multiple equality comparisons

Testing the equality of an object against another is fairly simple, just do foo == "bar". However, I usually try to test against multiple objects in a slightly different way. Your first thought might be that the easiest way is just to chain a series of == with the OR (||) operator.

foo == "bar" || foo == "baz" || foo == :sed || foo == 5

I much prefer to flip it around, think of the objects I’m testing against as a collection (Array), and then ask them if they contain the object I’m checking. And for that, I use Array#include?

    ["bar", "baz", :sed, 5].include?(foo)

(And if you’re only testing against strings, you could use %w(bar baz) as a shortcut to create the array. Here’s more ruby shortcuts.)

Assigning multiple items from a nested hash to variables

Occasionally I find myself needing to be given a hash of a hash of data (most recently, an omniauth auth hash) and assign some values from it to separate variables within my code. Given the following hash, containing a nested hash:

details = {
  uid: "12345",
  info: {
    name: "Caius Durling",
    nickname: "caius",

Lets say we want to extract the name and nickname fields from details[:info] hash into their own local variables (or instance variables within a class, more likely.) We should probably handle the case of details[:info] not being a hash, and try not to read from it if that’s the case - so we might end up with something like the following:

name = details[:info] && details[:info][:name]
nickname = details[:info] && details[:info][:nickname]

name # => "Caius Durling"
nickname # => "caius"

And then in the spirit of DRYing up our code, we see there’s duplication in both lines in checking details[:info] exists (not actually that it’s a hash, but hey ho, we rely on upstream to send us nil or a hash.) So we reduce it down using an if statement and give ourselves slightly less to type at the same time.

if (( info = details[:info] ))
  name = info[:name]
  nickname = info[:nickname]

name # => "Caius Durling"
nickname # => "caius"

Returning two values conditionally

Sometimes a method will end with a ternary, where depending on a condition it’ll either return one or another value. If this conditional returns true, then the first value is returned. Otherwise it returns the second value. You could quite easily write it out as an if/else longer-form block too.

def my_method
  @blah == foo ? :foo_matches : :no_match

My brain finds picking the logic in this apart slightly harder mentally, than if I drop a return early bomb on the method. Then it reads more akin to how I’d think through the logic. Return the first value if this conditional returns true. Otherwise the method returns this second value. I think the second value being on a completely separate line helps me make this mental distinction quicker too.

So I’d write it this way:

def my_method
  return :foo_matches if @blah == foo

Returning nil or a value conditionally

Following on from the last snippet, but taking advantage of the ruby runtime a bit more, is when you’re wanting to return a value if a conditional is true, or otherwise false. The easy way is to just write nil in the ternary:

def my_method
  @foo == :bar ? :foo_matches : nil

However, we know ruby returns the result of the last expression in the method. And that if a single line conditional isn’t met, it returns nil from the expression. Combining that, we can rewrite the previous example into this:

def my_method
  :foo_matches if @foo == :bar

And it will still return nil in the case that @foo doesn’t match :bar.

Returning a boolean

Sometimes you have a method that returns the result of a conditional, but it’s written to return true/false in a conditional instead.

def my_method @foo == :bar ? true : false end

The really easy refactor here is to just remove the ternary and leave the conditional.

def my_method @foo == :bar end

And of course if you were returning false when the conditional evaluates to true, you can either negate the comparison (use != in that example), or negate the entire conditional result by prepending ! to the line.