Simple Question


#1

I saw the following in a book.

def deleted_roles=(values)
roles.find(*values).each(&:destroy)
end

I understand that this method finds all the roles with the given ids and
calls destroy on all of them. My question is, what is the significance
of *. Why is it roles.find(*values) and not just plain
roles.find(values)?

Is there any difference?

Could it possibly be a typo and the method should be defined as

def deleted_roles(*values)…

Thanks


#2
  • expands an array as multiple arguments. For example, type in an irb
    session:

def find(*args) # This * is not the same * as yours, this is just used
to collect all the arguments in a single array
args.each {|x| puts x.class}
end

find [1,2,3] => Array
find *[1,2,3] => Fixnum three times.

Regards,

Serabe


#3

Hi,

Is there any difference?

Could it possibly be a typo and the method should be defined as

def deleted_roles(*values)…

It looks like roles.find expects a list of parameters (i.e. it should
be invoked like this: roles.find(‘admin’, ‘user’, ‘editor’))
but deleted_roles= wants an array (i.e. deleted_rows = [‘admin’,
‘user’, ‘editor’])

The * a.k.a. splat does exactly this conversion - so if someone calls

deleted_rows = [‘admin’, ‘user’, ‘editor’]

inside the method

roles.find(‘admin’, ‘user’, ‘editor’).each(&:destroy)

will be called (note that the brackets are gone)

HTH,
Peter


http://www.rubyrailways.com