array-dig.rb

client =  {client: { firstname: "bobby", lastname: "brown"}}

# Using the the [] getter
firstname = client[:client][:firstname]
=> "bobby"

# Using the new dig method, it gives you the 
# same result the best is coming
firstname = client.dig(:client, :firstname)
=> "bobby"

# Let's see what we got when the leading key doesn't exist
firstname = client[:customer][:firstname]
# Traceback (most recent call last):
#         2: from /usr/local/bin/irb:11:in `<main>'
#         1: from (irb):45
# NoMethodError (undefined method `[]' for nil:NilClass)

# And with the dig method what you got
firstname = client.dig(:customer, :firstname)
=> nil