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====
Don't use `||=` to initialize boolean variables.
(Consider what would happen if the current value happened to be `false`.)
[source,ruby]
----
# bad - would set enabled to true even if it was false
enabled ||= true
# good
enabled = true if enabled.nil?
----
====
=== Existence Check Shorthand [[double-amper-preprocess]]
Use `&&=` to preprocess variables that may or may not exist.
Using `&&=` will change the value only if it exists, removing the need to check its existence with `if`.
[source,ruby]
----
# bad
if something
something = something.downcase
end
# bad
something = something ? something.downcase : nil
# ok
something = something.downcase if something
# good
something = something && something.downcase
# better
something &&= something.downcase
----
=== Identity Comparison [[identity-comparison]]
Prefer `equal?` over `==` when comparing `object_id`. `Object#equal?` is provided to compare objects for identity, and in contrast `Object#==` is provided for the purpose of doing value comparison.
[source,ruby]
----
# bad
foo.object_id == bar.object_id
# good
foo.equal?(bar)
----
Similarly, prefer using `Hash#compare_by_identity` than using `object_id` for keys:
[source,ruby]
----
# bad
hash = {}
hash[foo.object_id] = :bar
if hash.key?(baz.object_id) # ...
# good
hash = {}.compare_by_identity
hash[foo] = :bar
if hash.key?(baz) # ...
----
Note that `Set` also has `Set#compare_by_identity` available.
=== Explicit Use of the Case Equality Operator [[no-case-equality]]
Avoid explicit use of the case equality operator `===`.
As its name implies it is meant to be used implicitly by `case` expressions and outside of them it yields some pretty confusing code.
[source,ruby]
----
# bad
Array === something
(1..100) === 7
/something/ === some_string
# good
something.is_a?(Array)
(1..100).include?(7)
some_string.match?(/something/)
----
NOTE: With direct subclasses of `BasicObject`, using `is_a?` is not an option since `BasicObject` doesn't provide that method (it's defined in `Object`). In those
rare cases it's OK to use `===`.
=== `is_a?` vs `kind_of?` [[is-a-vs-kind-of]]
Prefer `is_a?` over `kind_of?`. The two methods are synonyms, but `is_a?` is the more commonly used name in the wild.
[source,ruby]
----
# bad
something.kind_of?(Array)
# good