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mantot123
mantot123

Reputation: 203

Do methods have to be always inside classes in Ruby?

Hey guys I am new to Ruby. I have a question: Do methods have to be always inside classes?

Upvotes: 2

Views: 168

Answers (2)

Jörg W Mittag
Jörg W Mittag

Reputation: 369458

Hey guys I am new to Ruby. I have a question: Do methods have to be always inside classes?

No.

Methods have to be always inside modules. (Class are modules, too.)

Example:

module Foo
  def bar; end
end

There is no class here.

Upvotes: 2

ndnenkov
ndnenkov

Reputation: 36101

Technically they are aways defined inside a class, but this doesn't mean you always need to open a class to define a method.

Here is what might look like a top-level function in other languages:

def foo
  puts self
  puts self.class
end

If we simply call foo, we'll get:

main
Object

This actually defined a private instance method in the Object class. We see that self in the top-level scope is a special object called main.

On the other hand, we can try to call this method on other stuff:

'bar'.foo #!> private method `foo' called for "bar":String (NoMethodError)

This errorred out as foo is private. We can use a special method called send to invoke private methods:

'bar'.send :foo

Gets us:

bar
String

We can also define methods in the so-called singleton classes. You can think of them as classes with only a single instance. For example:

foo = 'foo'

def foo.bar
  puts 'baz'
end

foo.bar    # => baz
'quix'.bar # !> undefined method `bar' for "quix":String
'foo'.bar  # !> undefined method `bar' for "foo":String

puts (foo.singleton_class.instance_methods - Object.instance_methods).first
  # => bar

Here the bar method was defined on the singleton class of foo. Note that even another string with the same contents is still a difference instance, hence it doesn't have the bar method.

Upvotes: 2

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