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

Hiromi De Young
Hiromi De Young
2,294 Points
Posted by Hiromi De Young
Hiromi De Young
2,294 Points

Under the Ruby Boolean quiz, the question about a contains? method seems broken. Anyone else get it to work?

This code is 100% correct, yet the Ruby Boolean quiz refuses to accept it as a valid answer:

def contains?(name) @todo_items.include?(name) end

The system keeps saying "Bummer! The contains? method doesn't return a boolean value." Has anybody else been able to pass this question in order to move on?

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)
    @todo_items.include?(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

t = TodoList.new('MyList')
t.todo_items << "test"
puts t.contains? "test"

1 Answer

Tim Knight
Tim Knight
28,888 Points
Tim Knight
Tim Knight
28,888 Points

Hiromi,

What you have here is valid Ruby but I think they're looking for a little more from you. What if include? didn't exist? How would you check to see if todo_items contained a value? You'd iterate over the array.

def contains?(name)
  todo_items.each do |item|
    return true if item.name == name
  end
  return false
end
Adrian Manteza
Adrian Manteza
2,527 Points
Adrian Manteza
Adrian Manteza
2,527 Points

Hi Tim,

In the line

item.name == name ,is the .name a built in method? where is it defined?

Thanks

Tim Knight
Tim Knight
28,888 Points
Tim Knight
Tim Knight
28,888 Points

Adrian, the ".name" is the "name" reader attribute defined right in the beginning. It is the name of the todo_item within the todo_items array that we're looping through and comparing it to the local value of "name" that we're passing into the function of "contains?".

Heather Stone
Heather Stone
5,784 Points

Hi Tim, I'm working on this challenge and wondering why it's not else return false, rather than just return false. Is the default state of the program to assume that the array doesn't have the item? To get existential on you, why is else used in some applications and not others? It seems like this would be a good place for it.

Tim Knight
Tim Knight
28,888 Points
Tim Knight
Tim Knight
28,888 Points

Heather that's a really good question. The biggest thing to understand is that one you run a return in a method the method stops process anything else below it. So in this case we can just set a default return of false. If todo_items has an item that matchings the name value we just return true which stops the method and returns. It's really a syntactical choice. You could just as well do a tertiary operator if you wanted to which is like if/else shorthand

todo_items.each do |item|
  item.name == name ? return true : return false
end

Again though, it's really just a syntax choice. In my example we don't need else once it's true it'll stop... otherwise the else is inferred with the default return.