Pattern: Inefficient hash search
Issue: -
This rule checks for inefficient searching of keys and values within hashes.
Hash#keys.include? is less efficient than Hash#key? because
the former allocates a new array and then performs an O(n) search
through that array, while Hash#key? does not allocate any array and
performs a faster O(1) search for the key.
Hash#values.include? is less efficient than Hash#value?. While they
both perform an O(n) search through all of the values, calling values
allocates a new array while using value? does not.
# bad
{ a: 1, b: 2 }.keys.include?(:a)
{ a: 1, b: 2 }.keys.include?(:z)
h = { a: 1, b: 2 }; h.keys.include?(100)
# good
{ a: 1, b: 2 }.key?(:a)
{ a: 1, b: 2 }.has_key?(:z)
h = { a: 1, b: 2 }; h.key?(100)
# bad
{ a: 1, b: 2 }.values.include?(2)
{ a: 1, b: 2 }.values.include?('garbage')
h = { a: 1, b: 2 }; h.values.include?(nil)
# good
{ a: 1, b: 2 }.value?(2)
{ a: 1, b: 2 }.has_value?('garbage')
h = { a: 1, b: 2 }; h.value?(nil)