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gadams
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ruby

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# good
def do_something(params = {})
unless params[:when] == :later
output(options[:message])
end
end
end
----
=== Safe Assignment in Condition [[safe-assignment-in-condition]]
Don't use the return value of `=` (an assignment) in conditional expressions unless the assignment is wrapped in parentheses.
This is a fairly popular idiom among Rubyists that's sometimes referred to as _safe assignment in condition_.
[source,ruby]
----
# bad (+ a warning)
if v = array.grep(/foo/)
do_something(v)
# some code
end
# good (MRI would still complain, but RuboCop won't)
if (v = array.grep(/foo/))
do_something(v)
# some code
end
# good
v = array.grep(/foo/)
if v
do_something(v)
# some code
end
----
=== `BEGIN` Blocks [[no-BEGIN-blocks]]
Avoid the use of `BEGIN` blocks.
=== `END` Blocks [[no-END-blocks]]
Do not use `END` blocks. Use `Kernel#at_exit` instead.
[source,ruby]
----
# bad
END { puts 'Goodbye!' }
# good
at_exit { puts 'Goodbye!' }
----
=== Nested Conditionals [[no-nested-conditionals]]
Avoid use of nested conditionals for flow of control.
Prefer a guard clause when you can assert invalid data.
A guard clause is a conditional statement at the top of a function that bails out as soon as it can.
[source,ruby]
----
# bad
def compute_thing(thing)
if thing[:foo]
update_with_bar(thing[:foo])
if thing[:foo][:bar]
partial_compute(thing)
else
re_compute(thing)
end
end
end
# good
def compute_thing(thing)
return unless thing[:foo]
update_with_bar(thing[:foo])
return re_compute(thing) unless thing[:foo][:bar]
partial_compute(thing)
end
----
Prefer `next` in loops instead of conditional blocks.
[source,ruby]
----
# bad
[0, 1, 2, 3].each do |item|
if item > 1
puts item
end
end
# good
[0, 1, 2, 3].each do |item|
next unless item > 1
puts item
end