DigBang

Here’s Hash#dig! and Array#dig!. They're similar to Ruby’s Hash#dig and Array#dig, but they raise an exception instead of returning nil when a key isn’t found.

In a hash:

require 'dig_bang'

places = {
  world: {
    uk: true,
    usa: true
  }
}

# No difference when the key exists
places.dig  :world, :uk # true
places.dig! :world, :uk # true

# A relevant error when the key is missing
places.dig  :world, :uk, :alaska # nil
places.dig! :world, :uk, :alaska # KeyError: Key not found: :alaska

In an array:

airports = %w(lhr sfo nyc)

# Same result when the index is valid
airports.dig  2 # 'nyc'
airports.dig! 2 # 'nyc'

# A relevant error when the index is out of bounds
airports.dig  5 # nil
airports.dig! 5 # IndexError: index 5 outside of array bounds: -3...3

In a mixed data structure:

places = {
  world: {
    uk:  %w(lhr lgw man stn),
    usa: %w(nyc pdx sfo dca)
  }
}

places.dig  :world, :usa, 2 # 'sfo'
places.dig! :world, :usa, 2 # 'sfo'

places.dig  :world, :usa, 4 # nil
places.dig! :world, :usa, 6 # IndexError: index 6 outside of array bounds: -4...4

In combination with #dig:

places.dig!(:world, :usa).dig(6) # nil

The philosohy

#dig! is to #fetch as #dig is to #[]

Ruby 2.3 introduces the new Hash#dig method for safe extraction of a nested value. It’s the equivalent of a safely repeated Hash#[].

#dig!, on the other hand, is the equivalent of a safely repeated Hash#fetch. It’s “safely unsafe”😉 raising the appropriate KeyError anywhere down the line, or returning the value if it exists.

It's also just 18 lines of code.

Installation

Add this line to your application's Gemfile:

gem 'dig_bang'

And then execute:

$ bundle

Or install it yourself as:

$ gem install dig_bang

dig_bang

Development

DigBang

The philosohy

Installation