Ruby: (re)defining variables from another block/method?

Question

I don't know how exactly to word this, but I am trying to define many variables and then redefine them without rewriting each of the many variables and creating redundant code in each new block I write. The variables are defining array elements from multiple databases. Here is a downsized sample what I am working with:

def lots_of_vars(array)
  name = array[1]
  membership = array[2]
  spouse = array[3]
  ....
  lap12 = array[36]
end

def second_block
  #database1 => [ "Randy", true, "Nancy", 2, 17, false...
  lots_of_vars(database1)
  return unless membership
  puts "Lap progress for #{name} and #{spouse}: #{lap1}, #{lap2}... #{lap12}..."
end

def third_block
  #database2 => [ "Steven", true, nil, 0, 5, false...
  lots_of_vars(database2)
  return unless spouse.empty? or spouse.nil?
  puts "Weekly progress for #{name}: #{lap1}, #{lap5}, #{lap6}, #{lap10}..."
end

The second and third block need all the variables defined from the first block/method. But how do I pass all these variables? One example I read suggested I pass them all as parameters like:

def second_block(name, membership, spouse...)

but this would make just as much of a mess as defining each variable twice in both blocks. What is the simple, dry approach to such a situation? Please let me know if I need to clarify anything in my question, Thanks.

Matt Briggs · Accepted Answer · 2012-04-26 06:21:50Z

3

What you want is to create a Struct, which is a simple class to represent a datastructure. A struct will take its arguments in by position, which is exactly what you want, since you can splat the array into the method call (turn an array into an argument list)

So

Thing = Struct.new(:name, :membership, :spouse, :lap12)

array = ['Larry', 'gold', 'Sue', 2.2]
thing = Thing.new(*array)

#note that the splat (*) is equivalent to saying
# Thing.new(array[0], array[1], array[2], array[3])

thing.name # => "Larry"
thing.lap12 # => 2.2

answered Apr 26, 2012 at 6:21

Matt Briggs

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Comments

luacassus · Accepted Answer · 2012-04-26 07:43:56Z

0

Definitely approach with struct is one of the best.

Also you could do something like that:

HERE BE DRAGONS, DON'T TRY IT AT HOME! :)

class Foo

  def lots_of_vars(array)
    name = array[0]
    email = array[1]
    description = array[2]

    binding
  end

  def bar
    array = ['Luke', '[email protected]', 'Lorem ipsum']
    eval('"My name is #{name}, email: #{email}, here is description: #{description}"', lots_of_vars(array))
  end

end

foo = Foo.new
foo.bar

For more details you could check this nice blog post about ruby's binding http://onestepback.org/index.cgi/Tech/Ruby/RubyBindings.rdoc

answered Apr 26, 2012 at 7:43

luacassus

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1 Comment

luacassus Over a year ago

no problem, but please promise me that you won't use binding technique in your application ;)

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