Ruby/Rails FYI

Interpolation

2 min readOct 23, 2017

Interpolation automatically calls to_s, so the to_s calls in this sample text are unnecessary.

def s3_filename(record)
  name = record.name || 'Empty '
  date = Date.today.to_s
  guid = UUIDTools::UUID.random_create.to_s
  "#{name}-#{date}-#{guid}.txt"
end

Beginning or ending n characters of a word

If you see things like word[0..4] or word[5..-1], you can instead use Rails ActiveSupport methods like first, last, to, and from.

Suppose word = 'foobar'.

word.first(2) # fo
word.to(2) # foo
word.first(-2) # foob
word.to(-2) # fooba
word.last(2) # ar
word.from(2) # obar
word.last(-2) # obar
word.from(-2) # ar

Avoid []

Avoid calling my_hash[key]. If the key isn’t defined, you’ll get nil. This can lead to confusing errors:

user = my_hash[:user]
# Tens or hundreds of unrelated lines, then...
user.name # NoMethodError: undefined method `name' for nil:NilClass

Imagine you had this instead.

user = my_hash.fetch(:user) # KeyError: key not found: :user

That’s much clearer and makes for easier debugging.

Even if the key might not be defined, you should still use fetch, because then it will communicate that possibility to future readers. Like this:
my_hash.fetch(:key_that_might_not_be_present, nil)
If you’re dealing with a params object, there’s a better more specific method than fetch, which is params.require.

If this seems a little verbose or your skeptical about the benefits, here are some other arguments to consider, from some of the most experienced Rubyists I’ve ever encountered.

Gary’s tweet seems to have disappeared. It was:

Ruby’s `[]` operator should almost never be used. You will die. Do `x.fetch(k)`. If you really want nil by default, do `x.fetch(k) { nil }`.

Superfluous begin/end

People often write unnecessary begin/end blocks, e.g.

def foobar
  begin
    # do a thing which may fail
  rescue => e
    # do some exception handling
  end
end# That can be written simply as:
def foobar
 # do a thing which may fail
rescue => e
 # do some exception handling
end

Associations vs. ID’s

Bad: FactoryGirl.create(:user, company_id: company.id)
Good: FactoryGirl.create(:user, company: company)

Bad: validates(:company_id)
Good: validates(:company)