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NOTE: Ruby 3 introduced an alternative syntax for single-line method definitions, that's discussed in the next section
of the guide.
[source,ruby]
----
# bad
def too_much; something; something_else; end
# okish - notice that the first ; is required
def no_braces_method; body end
# okish - notice that the second ; is optional
def no_braces_method; body; end
# okish - valid syntax, but no ; makes it kind of hard to read
def some_method() body end
# good
def some_method
body
end
----
One exception to the rule are empty-body methods.
[source,ruby]
----
# good
def no_op; end
----
=== Endless Methods
Only use Ruby 3.0's endless method definitions with a single line
body. Ideally, such method definitions should be both simple (a
single expression) and free of side effects.
NOTE: It's important to understand that this guideline doesn't
contradict the previous one. We still caution against the use of
single-line method definitions, but if such methods are to be used,
prefer endless methods.
[source,ruby]
----
# bad
def fib(x) = if x < 2
x
else
fib(x - 1) + fib(x - 2)
end
# good
def the_answer = 42
def get_x = @x
def square(x) = x * x
# Not (so) good: has side effect
def set_x(x) = (@x = x)
def print_foo = puts("foo")
----
=== Double Colons [[double-colons]]
Use `::` only to reference constants (this includes classes and modules) and constructors (like `Array()` or `Nokogiri::HTML()`).
Do not use `::` for regular method calls.
[source,ruby]
----
# bad
SomeClass::some_method
some_object::some_method
# good
SomeClass.some_method
some_object.some_method
SomeModule::SomeClass::SOME_CONST
SomeModule::SomeClass()
----
=== Colon Method Definition [[colon-method-definition]]
Do not use `::` to define class methods.
[source,ruby]
----
# bad
class Foo
def self::some_method
end
end
# good
class Foo
def self.some_method
end
end
----
=== Method Definition Parentheses [[method-parens]]