Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Ruby Ruby Booleans Build a Simple Todo List Program Returning Boolean Values: Part 2

Posted by Chris Galatis
Chris Galatis
3,089 Points

When we give a method an argument, what is the argument actually doing?

I am a bit confused as to what the argument is used for when we define a method

todo_list.rb 
class TodoList
  attr_reader :name, :todo_items

  def initialize(name)
    @name = name
    @todo_items = []
  end

  def add_item(name)
    todo_items.push(TodoItem.new(name))
  end

  def contains?(name)
  end

  def find_index(name)
    index = 0
    found = false
        todo_items.each do |item|
      found = true if item.name == name
      break if found
      index += 1
    end
    if found
      return index
    else
      return nil
    end
  end
end

2 Answers

Dylan Shine
Dylan Shine
17,565 Points
Dylan Shine
Dylan Shine
17,565 Points

When we provide an argument to a method in Ruby, we are creating a local variable for our method to use/operate on the method object we provided.

def initialize(name)
    @name = name
    @todo_items = []
  end

For the standard initialize method, we provide an argument called name, probably in the form of a String, that we will use to assign the instance variable @name. We are simply passing a variable or value to that method, and the method will do something with or to it.

my_num = 1
def do_something_to_num(number)
  number *= 2
end

do_something_to_num(my_num) #=> 2

Here we create a variable my_num, and define a method do_something_to_num that takes one argument, number. Second we invoke the our newly defined method, passing in the variable my_num for it's argument.

To answer your question, arguments are representing/providing values for our methods, so your methods can perform whatever their trying to do.

Best,

Dylan

Chris Galatis
Chris Galatis
3,089 Points
Chris Galatis
Chris Galatis
3,089 Points

so if i am understanding it right the arguments we give the methods are kind of like characteristics of the method? like the argument is what the method does? as in this code

my_num = 1 def do_something_to_num(number) number *= 2 end

do_something_to_num(my_num) #=> 2

so the do_something_to_num method is taking an argument (number) and that arguments multiples by 2. so when the do_something_to_num method is called in the second part, it takes the my_num variable that we set equal to 1 and *= 2 onto my_num if i am understanding correctly?