Error: Undefined local variable or method 'index'

Question

I'm getting this error when I run my code which is below. The question I have is why doesn't the code in the video run into this same error as index in the 'remove_item' method of the video is not defined either.

require "./todo_item.rb"

class TodoList

  attr_reader :name, :todo_items

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

  # creates new item by instantiating ToDoItem class and them added it to the todo_items array.
  def add_item(name)
    todo_items.push(TodoItem.new(name))
  end

  def remove_item(name)
    if index == find_index(name)
      todo_items.delete_at(index)
      return true
    else
      return false
    end
  end

  def mark_complete(name)

  end

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

end

todo_list = TodoList.new("Groceries")
todo_list.add_item("Milk")
todo_list.add_item("Eggs")

puts todo_list.inspect

if todo_list.remove_item("Eggs")
  puts "Eggs were removed from the list."
end
puts todo_list.inspect

Answer 1 · 2016-04-07T18:38:24Z

April 7, 2016 6:38pm

If you use == then you are comparing what the find_index() method returns with the value of index. But there is no local variable index in remove_item() and there is also no method called index that returns anything so it's impossible to make a comparison. However, with an assignment, =, you are assigning the return value of find_index() to index. This return value is either a number, which then ruby interprets it as true even if it is 0, or it is false. So in the end the if statement ends up working as expected:

if true
  some code to run
else
  some other code to run
end

Answer 2 · 2016-04-07T00:06:21Z

April 7, 2016 12:06am

In the remove_item() method the line:

if index == find_index(name)

should be:

if index = find_index(name)

Also, there is a logical problem with your find_index() method. In the else part you add one to index but then you return nil, so the loop will never go past the first item.

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Tijo Thomas

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Error: Undefined local variable or method 'index'

2 Answers

Kourosh Raeen

Kourosh Raeen

Kourosh Raeen

Kourosh Raeen

Tijo Thomas

Tijo Thomas